com.google.javascript.jscomp.RemoveUnusedCode Maven / Gradle / Ivy
Show all versions of com.liferay.frontend.js.minifier
/*
* Copyright 2008 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimap;
import com.google.javascript.jscomp.CodingConvention.SubclassRelationship;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import com.google.javascript.rhino.TypeI;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import javax.annotation.Nullable;
/**
* Garbage collection for variable and function definitions. Basically performs
* a mark-and-sweep type algorithm over the JavaScript parse tree.
*
* For each scope:
* (1) Scan the variable/function declarations at that scope.
* (2) Traverse the scope for references, marking all referenced variables.
* Unlike other compiler passes, this is a pre-order traversal, not a
* post-order traversal.
* (3) If the traversal encounters an assign without other side-effects,
* create a continuation. Continue the continuation iff the assigned
* variable is referenced.
* (4) When the traversal completes, remove all unreferenced variables.
*
* If it makes it easier, you can think of the continuations of the traversal
* as a reference graph. Each continuation represents a set of edges, where the
* source node is a known variable, and the destination nodes are lazily
* evaluated when the continuation is executed.
*
* This algorithm is similar to the algorithm used by {@code SmartNameRemoval}.
* {@code SmartNameRemoval} maintains an explicit graph of dependencies
* between global symbols. However, {@code SmartNameRemoval} cannot handle
* non-trivial edges in the reference graph ("A is referenced iff both B and C
* are referenced"), or local variables. {@code SmartNameRemoval} is also
* substantially more complicated because it tries to handle namespaces
* (which is largely unnecessary in the presence of {@code CollapseProperties}.
*
* This pass also uses a more complex analysis of assignments, where
* an assignment to a variable or a property of that variable does not
* necessarily count as a reference to that variable, unless we can prove
* that it modifies external state. This is similar to
* {@code FlowSensitiveInlineVariables}, except that it works for variables
* used across scopes.
*
* Multiple datastructures are used to accumulate nodes, some of which are
* later removed. Since some nodes encompass a subtree of nodes, the removal
* can sometimes pre-remove other nodes which are also referenced in these
* datastructures for later removal. Attempting double-removal violates scope
* change notification constraints so there is a desire to excise
* already-removed subtree nodes from these datastructures. But not all of the
* datastructures are conducive to flexible removal and the ones that are
* conducive don't necessarily track all flavors of nodes. So instead of
* updating datastructures on the fly a pre-check is performed to skip
* already-removed nodes right before the moment an attempt to remove them
* would otherwise be made.
*
* @author [email protected] (Nick Santos)
*/
class RemoveUnusedCode implements CompilerPass {
// Properties that are implicitly used as part of the JS language.
private static final ImmutableSet IMPLICITLY_USED_PROPERTIES =
ImmutableSet.of("length", "toString", "valueOf", "constructor");
private final AbstractCompiler compiler;
private final CodingConvention codingConvention;
private final boolean removeLocalVars;
private final boolean removeGlobals;
private final boolean preserveFunctionExpressionNames;
/**
* Used to hold continuations that need to be invoked.
*
* When we find a subtree of the AST that may not need to be traversed, we create a Continuation
* for it. If we later discover that we do need to traverse it, we add it to this worklist
* rather than traversing it immediately. If we invoked the traversal immediately, we could
* end up modifying a data structure in the traversal as we're iterating over it.
*/
private final Deque worklist = new ArrayDeque<>();
private final Map varInfoMap = new HashMap<>();
private final Set referencedPropertyNames = new HashSet<>(IMPLICITLY_USED_PROPERTIES);
/** Stores Removable objects for each property name that is currently considered removable. */
private final Multimap removablesForPropertyNames = HashMultimap.create();
/** Single value to use for all vars for which we cannot remove anything at all. */
private final VarInfo canonicalUnremovableVarInfo;
/**
* Keep track of scopes that we've traversed.
*/
private final List allFunctionParamScopes = new ArrayList<>();
private final Es6SyntacticScopeCreator scopeCreator;
private final boolean removeUnusedPrototypeProperties;
private final boolean allowRemovalOfExternProperties;
private final boolean removeUnusedThisProperties;
private final boolean removeUnusedStaticProperties;
private final boolean removeUnusedObjectDefinePropertiesDefinitions;
RemoveUnusedCode(Builder builder) {
this.compiler = builder.compiler;
this.codingConvention = builder.compiler.getCodingConvention();
this.removeLocalVars = builder.removeLocalVars;
this.removeGlobals = builder.removeGlobals;
this.preserveFunctionExpressionNames = builder.preserveFunctionExpressionNames;
this.removeUnusedPrototypeProperties = builder.removeUnusedPrototypeProperties;
this.allowRemovalOfExternProperties = builder.allowRemovalOfExternProperties;
this.removeUnusedThisProperties = builder.removeUnusedThisProperties;
this.removeUnusedStaticProperties = builder.removeUnusedStaticProperties;
this.removeUnusedObjectDefinePropertiesDefinitions =
builder.removeUnusedObjectDefinePropertiesDefinitions;
this.scopeCreator = new Es6SyntacticScopeCreator(builder.compiler);
// All Vars that are completely unremovable will share this VarInfo instance.
canonicalUnremovableVarInfo = new VarInfo();
canonicalUnremovableVarInfo.setIsExplicitlyNotRemovable();
}
public static class Builder {
private final AbstractCompiler compiler;
private boolean removeLocalVars = false;
private boolean removeGlobals = false;
private boolean preserveFunctionExpressionNames = false;
private boolean removeUnusedPrototypeProperties = false;
private boolean allowRemovalOfExternProperties = false;
private boolean removeUnusedThisProperties = false;
private boolean removeUnusedStaticProperties = false;
private boolean removeUnusedObjectDefinePropertiesDefinitions = false;
Builder(AbstractCompiler compiler) {
this.compiler = compiler;
}
Builder removeLocalVars(boolean value) {
this.removeLocalVars = value;
return this;
}
Builder removeGlobals(boolean value) {
this.removeGlobals = value;
return this;
}
Builder preserveFunctionExpressionNames(boolean value) {
this.preserveFunctionExpressionNames = value;
return this;
}
Builder removeUnusedPrototypeProperties(boolean value) {
this.removeUnusedPrototypeProperties = value;
return this;
}
Builder allowRemovalOfExternProperties(boolean value) {
this.allowRemovalOfExternProperties = value;
return this;
}
Builder removeUnusedThisProperties(boolean value) {
this.removeUnusedThisProperties = value;
return this;
}
Builder removeUnusedConstructorProperties(boolean value) {
this.removeUnusedStaticProperties = value;
return this;
}
Builder removeUnusedObjectDefinePropertiesDefinitions(boolean value) {
this.removeUnusedObjectDefinePropertiesDefinitions = value;
return this;
}
RemoveUnusedCode build() {
return new RemoveUnusedCode(this);
}
}
/**
* Traverses the root, removing all unused variables. Multiple traversals
* may occur to ensure all unused variables are removed.
*/
@Override
public void process(Node externs, Node root) {
checkState(compiler.getLifeCycleStage().isNormalized());
if (!allowRemovalOfExternProperties) {
referencedPropertyNames.addAll(compiler.getExternProperties());
}
traverseAndRemoveUnusedReferences(root);
}
/**
* Traverses a node recursively. Call this once per pass.
*/
private void traverseAndRemoveUnusedReferences(Node root) {
// Create scope from parent of root node, which also has externs as a child, so we'll
// have extern definitions in scope.
Scope scope = scopeCreator.createScope(root.getParent(), null);
if (!scope.isDeclared(NodeUtil.JSC_PROPERTY_NAME_FN, /* recurse */ true)) {
// TODO(b/70730762): Passes that add references to this should ensure it is declared.
// NOTE: null input makes this an extern var.
scope.declare(
NodeUtil.JSC_PROPERTY_NAME_FN, /* no declaration node */ null, /* no input */ null);
}
worklist.add(new Continuation(root, scope));
while (!worklist.isEmpty()) {
Continuation continuation = worklist.remove();
continuation.apply();
}
removeUnreferencedVars();
removeIndependentlyRemovableProperties();
for (Scope fparamScope : allFunctionParamScopes) {
removeUnreferencedFunctionArgs(fparamScope);
}
}
private void removeIndependentlyRemovableProperties() {
for (Removable removable : removablesForPropertyNames.values()) {
removable.remove(compiler);
}
}
/**
* Traverses everything in the current scope and marks variables that
* are referenced.
*
* During traversal, we identify subtrees that will only be
* referenced if their enclosing variables are referenced. Instead of
* traversing those subtrees, we create a continuation for them,
* and traverse them lazily.
*/
private void traverseNode(Node n, Scope scope) {
Node parent = n.getParent();
Token type = n.getToken();
switch (type) {
case CATCH:
traverseCatch(n, scope);
break;
case FUNCTION:
{
VarInfo varInfo = null;
// If this function is a removable var, then create a continuation
// for it instead of traversing immediately.
if (NodeUtil.isFunctionDeclaration(n)) {
varInfo = traverseNameNode(n.getFirstChild(), scope);
FunctionDeclaration functionDeclaration =
new RemovableBuilder()
.addContinuation(new Continuation(n, scope))
.buildFunctionDeclaration(n);
varInfo.addRemovable(functionDeclaration);
if (parent.isExport()) {
varInfo.markAsReferenced();
}
} else {
traverseFunction(n, scope);
}
}
break;
case ASSIGN:
traverseAssign(n, scope);
break;
case ASSIGN_BITOR:
case ASSIGN_BITXOR:
case ASSIGN_BITAND:
case ASSIGN_LSH:
case ASSIGN_RSH:
case ASSIGN_URSH:
case ASSIGN_ADD:
case ASSIGN_SUB:
case ASSIGN_MUL:
case ASSIGN_EXPONENT:
case ASSIGN_DIV:
case ASSIGN_MOD:
traverseCompoundAssign(n, scope);
break;
case INC:
case DEC:
traverseIncrementOrDecrementOp(n, scope);
break;
case CALL:
traverseCall(n, scope);
break;
case SWITCH:
case BLOCK:
// This case if for if there are let and const variables in block scopes.
// Otherwise other variables will be hoisted up into the global scope and already be
// handled.
traverseChildren(
n, NodeUtil.createsBlockScope(n) ? scopeCreator.createScope(n, scope) : scope);
break;
case MODULE_BODY:
traverseChildren(n, scopeCreator.createScope(n, scope));
break;
case CLASS:
traverseClass(n, scope);
break;
case CLASS_MEMBERS:
traverseClassMembers(n, scope);
break;
case DEFAULT_VALUE:
traverseDefaultValue(n, scope);
break;
case REST:
traverseRest(n, scope);
break;
case ARRAY_PATTERN:
traverseArrayPattern(n, scope);
break;
case OBJECT_PATTERN:
traverseObjectPattern(n, scope);
break;
case OBJECTLIT:
traverseObjectLiteral(n, scope);
break;
case FOR:
traverseVanillaFor(n, scope);
break;
case FOR_IN:
case FOR_OF:
traverseEnhancedFor(n, scope);
break;
case LET:
case CONST:
case VAR:
// for-loop cases are handled by custom traversal methods.
checkState(NodeUtil.isStatement(n));
traverseDeclarationStatement(n, scope);
break;
case INSTANCEOF:
traverseInstanceof(n, scope);
break;
case NAME:
// The only cases that should reach this point are parameter declarations and references
// to names. The name node does not have children in these cases.
checkState(!n.hasChildren());
// the parameter declaration is not a read of the name
if (!parent.isParamList()) {
// var|let|const name;
// are handled at a higher level.
checkState(!NodeUtil.isNameDeclaration(parent));
// function name() {}
// class name() {}
// handled at a higher level
checkState(!((parent.isFunction() || parent.isClass()) && parent.getFirstChild() == n));
traverseNameNode(n, scope).markAsReferenced();
}
break;
case GETPROP:
traverseGetProp(n, scope);
break;
default:
traverseChildren(n, scope);
break;
}
}
private void traverseInstanceof(Node instanceofNode, Scope scope) {
checkArgument(instanceofNode.isInstanceOf(), instanceofNode);
Node lhs = instanceofNode.getFirstChild();
Node rhs = lhs.getNext();
traverseNode(lhs, scope);
if (rhs.isName()) {
VarInfo varInfo = traverseNameNode(rhs, scope);
RemovableBuilder builder = new RemovableBuilder();
varInfo.addRemovable(builder.buildInstanceofName(instanceofNode));
} else {
traverseNode(rhs, scope);
}
}
private void traverseGetProp(Node getProp, Scope scope) {
Node objectNode = getProp.getFirstChild();
Node propertyNameNode = objectNode.getNext();
String propertyName = propertyNameNode.getString();
if (NodeUtil.isExpressionResultUsed(getProp)) {
// must record as reference to the property and continue traversal.
markPropertyNameReferenced(propertyName);
traverseNode(objectNode, scope);
} else if (objectNode.isThis()) {
// this.propName;
RemovableBuilder builder = new RemovableBuilder().setIsThisDotPropertyReference(true);
considerForIndependentRemoval(builder.buildUnusedReadReference(getProp, propertyNameNode));
} else if (isDotPrototype(objectNode)) {
// (objExpression).prototype.propName;
RemovableBuilder builder = new RemovableBuilder().setIsPrototypeDotPropertyReference(true);
Node objExpression = objectNode.getFirstChild();
if (objExpression.isName()) {
// name.prototype.propName;
VarInfo varInfo = traverseNameNode(objExpression, scope);
varInfo.addRemovable(builder.buildUnusedReadReference(getProp, propertyNameNode));
} else {
// (objExpression).prototype.propName;
if (NodeUtil.mayHaveSideEffects(objExpression)) {
traverseNode(objExpression, scope);
} else {
builder.addContinuation(new Continuation(objExpression, scope));
}
considerForIndependentRemoval(builder.buildUnusedReadReference(getProp, propertyNameNode));
}
} else {
// TODO(bradfordcsmith): add removal of `varName.propName;`
markPropertyNameReferenced(propertyName);
traverseNode(objectNode, scope);
}
}
private void traverseIncrementOrDecrementOp(Node incOrDecOp, Scope scope) {
checkArgument(incOrDecOp.isInc() || incOrDecOp.isDec(), incOrDecOp);
Node arg = incOrDecOp.getOnlyChild();
if (NodeUtil.isExpressionResultUsed(incOrDecOp)) {
// If expression result is used, then this expression is definitely not removable.
traverseNode(arg, scope);
} else if (arg.isGetProp()) {
Node getPropObj = arg.getFirstChild();
Node propertyNameNode = arg.getLastChild();
if (getPropObj.isThis()) {
// this.propName++
RemovableBuilder builder = new RemovableBuilder().setIsThisDotPropertyReference(true);
considerForIndependentRemoval(builder.buildIncOrDepOp(incOrDecOp, propertyNameNode));
} else if (isDotPrototype(getPropObj)) {
// someExpression.prototype.propName++
Node exprObj = getPropObj.getFirstChild();
RemovableBuilder builder = new RemovableBuilder().setIsPrototypeDotPropertyReference(true);
if (exprObj.isName()) {
// varName.prototype.propName++
VarInfo varInfo = traverseNameNode(exprObj, scope);
varInfo.addRemovable(builder.buildIncOrDepOp(incOrDecOp, propertyNameNode));
} else {
// (someExpression).prototype.propName++
if (NodeUtil.mayHaveSideEffects(exprObj)) {
traverseNode(exprObj, scope);
} else {
builder.addContinuation(new Continuation(exprObj, scope));
}
considerForIndependentRemoval(builder.buildIncOrDepOp(incOrDecOp, propertyNameNode));
}
} else {
// someExpression.propName++ is not removable except in the cases covered above
traverseNode(arg, scope);
}
} else {
// TODO(bradfordcsmith): varName++ should be removable if varName is otherwise unused
traverseNode(arg, scope);
}
}
private void traverseCompoundAssign(Node compoundAssignNode, Scope scope) {
// We'll allow removal of compound assignment to a this property as long as the result of the
// assignment is unused.
// e.g. `this.x += 3;`
Node targetNode = compoundAssignNode.getFirstChild();
Node valueNode = compoundAssignNode.getLastChild();
if (targetNode.isGetProp()
&& targetNode.getFirstChild().isThis()
&& !NodeUtil.isExpressionResultUsed(compoundAssignNode)) {
RemovableBuilder builder = new RemovableBuilder().setIsThisDotPropertyReference(true);
traverseRemovableAssignValue(valueNode, builder, scope);
considerForIndependentRemoval(
builder.buildNamedPropertyAssign(compoundAssignNode, targetNode.getLastChild()));
} else {
traverseNode(targetNode, scope);
traverseNode(valueNode, scope);
}
}
private VarInfo traverseNameNode(Node n, Scope scope) {
return traverseVar(getVarForNameNode(n, scope));
}
private void traverseCall(Node callNode, Scope scope) {
Node callee = callNode.getFirstChild();
if (callee.isQualifiedName()
&& codingConvention.isPropertyRenameFunction(callee.getOriginalQualifiedName())) {
Node propertyNameNode = checkNotNull(callee.getNext());
if (propertyNameNode.isString()) {
markPropertyNameReferenced(propertyNameNode.getString());
}
traverseChildren(callNode, scope);
} else if (NodeUtil.isObjectDefinePropertiesDefinition(callNode)) {
// TODO(bradfordcsmith): Should also handle Object.create() and Object.defineProperty().
traverseObjectDefinePropertiesCall(callNode, scope);
} else {
Node parent = callNode.getParent();
String classVarName = null;
// A call that is a statement unto itself or the left side of a comma expression might be
// a call to a known method for doing class setup
// e.g. $jscomp.inherits(Class, BaseClass) or goog.addSingletonGetter(Class)
// Such methods never have meaningful return values, so we won't look for them in other
// contexts
if (parent.isExprResult() || (parent.isComma() && parent.getFirstChild() == callNode)) {
SubclassRelationship subclassRelationship =
codingConvention.getClassesDefinedByCall(callNode);
if (subclassRelationship != null) {
// e.g. goog.inherits(DerivedClass, BaseClass);
// NOTE: DerivedClass and BaseClass must be QNames. Otherwise getClassesDefinedByCall()
// will return null.
classVarName = subclassRelationship.subclassName;
} else {
// Look for calls to addSingletonGetter calls.
classVarName = codingConvention.getSingletonGetterClassName(callNode);
}
}
Var classVar = null;
if (classVarName != null && NodeUtil.isValidSimpleName(classVarName)) {
classVar = checkNotNull(scope.getVar(classVarName), classVarName);
}
if (classVar == null || !classVar.isGlobal()) {
// The call we are traversing does not modify a class definition,
// or the class is not specified with a simple variable name,
// or the variable name is not global.
// TODO(bradfordcsmith): It would be more correct to check whether the class name
// references a known constructor and expand to allow QNames.
traverseChildren(callNode, scope);
} else {
RemovableBuilder builder = new RemovableBuilder();
for (Node child = callNode.getFirstChild(); child != null; child = child.getNext()) {
builder.addContinuation(new Continuation(child, scope));
}
traverseVar(classVar).addRemovable(builder.buildClassSetupCall(callNode));
}
}
}
/** Traverse `Object.defineProperties(someObject, propertyDefinitions);`. */
private void traverseObjectDefinePropertiesCall(Node callNode, Scope scope) {
// First child is Object.defineProperties or some equivalent of it.
Node callee = callNode.getFirstChild();
Node targetObject = callNode.getSecondChild();
Node propertyDefinitions = targetObject.getNext();
if ((targetObject.isName() || isNameDotPrototype(targetObject))
&& !NodeUtil.isExpressionResultUsed(callNode)) {
// NOTE: Object.defineProperties() returns its first argument, so if its return value is used
// that counts as a use of the targetObject.
Node nameNode = targetObject.isName() ? targetObject : targetObject.getFirstChild();
VarInfo varInfo = traverseNameNode(nameNode, scope);
RemovableBuilder builder = new RemovableBuilder();
// TODO(bradfordcsmith): Is it really necessary to traverse the callee
// (aka. Object.defineProperties)?
builder.addContinuation(new Continuation(callee, scope));
if (NodeUtil.mayHaveSideEffects(propertyDefinitions)) {
traverseNode(propertyDefinitions, scope);
} else {
builder.addContinuation(new Continuation(propertyDefinitions, scope));
}
varInfo.addRemovable(builder.buildClassSetupCall(callNode));
} else {
// TODO(bradfordcsmith): Is it really necessary to traverse the callee
// (aka. Object.defineProperties)?
traverseNode(callee, scope);
traverseNode(targetObject, scope);
traverseNode(propertyDefinitions, scope);
}
}
/** Traverse the object literal passed as the second argument to `Object.defineProperties()`. */
private void traverseObjectDefinePropertiesLiteral(Node propertyDefinitions, Scope scope) {
for (Node property = propertyDefinitions.getFirstChild();
property != null;
property = property.getNext()) {
if (property.isQuotedString()) {
// Quoted property name counts as a reference to the property and protects it from removal.
markPropertyNameReferenced(property.getString());
traverseNode(property.getOnlyChild(), scope);
} else if (property.isStringKey()) {
Node definition = property.getOnlyChild();
if (NodeUtil.mayHaveSideEffects(definition)) {
traverseNode(definition, scope);
} else {
considerForIndependentRemoval(
new RemovableBuilder()
.addContinuation(new Continuation(definition, scope))
.buildObjectDefinePropertiesDefinition(property));
}
} else {
// TODO(bradfordcsmith): Maybe report error for anything other than a computed property,
// since getters, setters, and methods don't make much sense in this context.
traverseNode(property, scope);
}
}
}
private void traverseRest(Node restNode, Scope scope) {
Node target = restNode.getOnlyChild();
if (target.isName()) {
VarInfo varInfo = traverseNameNode(target, scope);
if (!restNode.getParent().isParamList()) {
// Parameter removal is done in removeUnreferencedFunctionArgs().
// TODO(bradfordcsmith): Handle parameter placeholders with removables for better code
// consistency.
varInfo.addRemovable(new RemovableBuilder().buildDestructuringAssign(target));
}
} else if (isThisDotProperty(target)) {
considerForIndependentRemoval(new RemovableBuilder().buildDestructuringAssign(target));
} else {
traverseNode(target, scope);
}
}
private Var getVarForNameNode(Node nameNode, Scope scope) {
return checkNotNull(scope.getVar(nameNode.getString()), nameNode);
}
private void traverseObjectLiteral(Node objectLiteral, Scope scope) {
checkArgument(objectLiteral.isObjectLit(), objectLiteral);
// Is this an object literal that is assigned directly to a 'prototype' property?
if (isAssignmentToPrototype(objectLiteral.getParent())) {
traversePrototypeLiteral(objectLiteral, scope);
} else if (isObjectDefinePropertiesSecondArgument(objectLiteral)) {
// TODO(bradfordcsmith): Consider restricting special handling of the properties literal to
// cases where the target object is a known class, prototype, or this.
traverseObjectDefinePropertiesLiteral(objectLiteral, scope);
} else {
traverseNonPrototypeObjectLiteral(objectLiteral, scope);
}
}
private boolean isObjectDefinePropertiesSecondArgument(Node n) {
Node parent = n.getParent();
return NodeUtil.isObjectDefinePropertiesDefinition(parent) && parent.getLastChild() == n;
}
private void traverseNonPrototypeObjectLiteral(Node objectLiteral, Scope scope) {
for (Node propertyNode = objectLiteral.getFirstChild();
propertyNode != null;
propertyNode = propertyNode.getNext()) {
if (propertyNode.isStringKey()) {
// A property name in an object literal counts as a reference,
// because of some reflection patterns.
// Note that we are intentionally treating both quoted and unquoted keys as
// references.
markPropertyNameReferenced(propertyNode.getString());
traverseNode(propertyNode.getFirstChild(), scope);
} else {
traverseNode(propertyNode, scope);
}
}
}
private void traversePrototypeLiteral(Node objectLiteral, Scope scope) {
for (Node propertyNode = objectLiteral.getFirstChild();
propertyNode != null;
propertyNode = propertyNode.getNext()) {
if (propertyNode.isComputedProp() || propertyNode.isQuotedString()) {
traverseChildren(propertyNode, scope);
} else {
Node valueNode = propertyNode.getOnlyChild();
if (NodeUtil.mayHaveSideEffects(valueNode)) {
// TODO(bradfordcsmith): Ideally we should preserve the side-effect without keeping the
// property itself alive.
traverseNode(valueNode, scope);
} else {
// If we've come this far, we already know we're keeping the prototype literal itself,
// but we may be able to remove unreferenced properties in it.
considerForIndependentRemoval(
new RemovableBuilder()
.addContinuation(new Continuation(valueNode, scope))
.buildClassOrPrototypeNamedProperty(propertyNode));
}
}
}
}
private boolean isAssignmentToPrototype(Node n) {
return n.isAssign() && isDotPrototype(n.getFirstChild());
}
/** True for `someExpression.prototype`. */
private static boolean isDotPrototype(Node n) {
return n.isGetProp() && n.getLastChild().getString().equals("prototype");
}
private void traverseCatch(Node catchNode, Scope scope) {
Node exceptionNameNode = catchNode.getFirstChild();
Node block = exceptionNameNode.getNext();
VarInfo exceptionVarInfo = traverseNameNode(exceptionNameNode, scope);
exceptionVarInfo.setIsExplicitlyNotRemovable();
traverseNode(block, scope);
}
private void traverseEnhancedFor(Node enhancedFor, Scope scope) {
Scope forScope = scopeCreator.createScope(enhancedFor, scope);
// for (iterationTarget in|of collection) body;
Node iterationTarget = enhancedFor.getFirstChild();
Node collection = iterationTarget.getNext();
Node body = collection.getNext();
if (iterationTarget.isName()) {
// using previously-declared loop variable. e.g.
// `for (varName of collection) {}`
VarInfo varInfo = traverseNameNode(iterationTarget, forScope);
varInfo.setIsExplicitlyNotRemovable();
} else if (NodeUtil.isNameDeclaration(iterationTarget)) {
// loop has const/var/let declaration
Node declNode = iterationTarget.getOnlyChild();
if (declNode.isDestructuringLhs()) {
// e.g.
// `for (const [a, b] of pairList) {}`
// destructuring is handled at a lower level
// Note that destructuring assignments are always considered to set an unknown value
// equivalent to what we set for the var name case above and below.
// It isn't necessary to set the variable names as not removable, though, because the
// thing that isn't removable is the destructuring pattern itself, which we never remove.
// TODO(bradfordcsmith): The need to explain all the above shows this should be reworked.
traverseNode(declNode, forScope);
} else {
// e.g.
// `for (const varName of collection) {}`
checkState(declNode.isName());
checkState(!declNode.hasChildren());
// We can never remove the loop variable of a for-in or for-of loop, because it's
// essential to loop syntax.
VarInfo varInfo = traverseNameNode(declNode, forScope);
varInfo.setIsExplicitlyNotRemovable();
}
} else {
// using some general LHS value e.g.
// `for ([a, b] of collection) {}` destructuring with existing vars
// `for (a.x of collection) {}` using a property as the loop var
// TODO(bradfordcsmith): This should be considered a write if it's a property reference.
traverseNode(iterationTarget, forScope);
}
traverseNode(collection, forScope);
traverseNode(body, forScope);
}
private void traverseVanillaFor(Node forNode, Scope scope) {
Scope forScope = scopeCreator.createScope(forNode, scope);
Node initialization = forNode.getFirstChild();
Node condition = initialization.getNext();
Node update = condition.getNext();
Node block = update.getNext();
if (NodeUtil.isNameDeclaration(initialization)) {
traverseVanillaForNameDeclarations(initialization, forScope);
} else {
traverseNode(initialization, forScope);
}
traverseNode(condition, forScope);
traverseNode(update, forScope);
traverseNode(block, forScope);
}
private void traverseVanillaForNameDeclarations(Node nameDeclaration, Scope scope) {
for (Node child = nameDeclaration.getFirstChild(); child != null; child = child.getNext()) {
if (!child.isName()) {
// TODO(bradfordcsmith): Customize handling of destructuring
traverseNode(child, scope);
} else {
Node nameNode = child;
@Nullable Node valueNode = child.getFirstChild();
VarInfo varInfo = traverseNameNode(nameNode, scope);
if (valueNode == null) {
varInfo.addRemovable(new RemovableBuilder().buildVanillaForNameDeclaration(nameNode));
} else if (NodeUtil.mayHaveSideEffects(valueNode)) {
// TODO(bradfordcsmith): Actually allow for removing the variable while keeping the
// valueNode for its side-effects.
varInfo.setIsExplicitlyNotRemovable();
traverseNode(valueNode, scope);
} else {
VanillaForNameDeclaration vanillaForNameDeclaration =
new RemovableBuilder()
.addContinuation(new Continuation(valueNode, scope))
.buildVanillaForNameDeclaration(nameNode);
varInfo.addRemovable(vanillaForNameDeclaration);
}
}
}
}
private void traverseDeclarationStatement(Node declarationStatement, Scope scope) {
// Normalization should ensure that declaration statements always have just one child.
Node nameNode = declarationStatement.getOnlyChild();
if (!nameNode.isName()) {
// Destructuring declarations are handled elsewhere.
traverseNode(nameNode, scope);
} else {
Node valueNode = nameNode.getFirstChild();
VarInfo varInfo = traverseNameNode(nameNode, scope);
RemovableBuilder builder = new RemovableBuilder();
if (valueNode == null) {
varInfo.addRemovable(builder.buildNameDeclarationStatement(declarationStatement));
} else {
if (NodeUtil.mayHaveSideEffects(valueNode)) {
traverseNode(valueNode, scope);
} else {
builder.addContinuation(new Continuation(valueNode, scope));
}
NameDeclarationStatement removable =
builder.buildNameDeclarationStatement(declarationStatement);
varInfo.addRemovable(removable);
}
}
}
private void traverseAssign(Node assignNode, Scope scope) {
checkState(NodeUtil.isAssignmentOp(assignNode));
Node lhs = assignNode.getFirstChild();
Node valueNode = assignNode.getLastChild();
if (lhs.isName()) {
// varName = something
VarInfo varInfo = traverseNameNode(lhs, scope);
RemovableBuilder builder = new RemovableBuilder();
traverseRemovableAssignValue(valueNode, builder, scope);
varInfo.addRemovable(builder.buildVariableAssign(assignNode));
} else if (lhs.isGetElem()) {
Node getElemObj = lhs.getFirstChild();
Node getElemKey = lhs.getLastChild();
Node varNameNode =
getElemObj.isName()
? getElemObj
: isNameDotPrototype(getElemObj) ? getElemObj.getFirstChild() : null;
if (varNameNode != null) {
// varName[someExpression] = someValue
// OR
// varName.prototype[someExpression] = someValue
VarInfo varInfo = traverseNameNode(varNameNode, scope);
RemovableBuilder builder = new RemovableBuilder();
if (NodeUtil.mayHaveSideEffects(getElemKey)) {
traverseNode(getElemKey, scope);
} else {
builder.addContinuation(new Continuation(getElemKey, scope));
}
traverseRemovableAssignValue(valueNode, builder, scope);
varInfo.addRemovable(builder.buildComputedPropertyAssign(assignNode, getElemKey));
} else {
traverseNode(getElemObj, scope);
traverseNode(getElemKey, scope);
traverseNode(valueNode, scope);
}
} else if (lhs.isGetProp()) {
Node getPropLhs = lhs.getFirstChild();
Node propNameNode = lhs.getLastChild();
if (getPropLhs.isName()) {
// varName.propertyName = someValue
VarInfo varInfo = traverseNameNode(getPropLhs, scope);
RemovableBuilder builder = new RemovableBuilder();
traverseRemovableAssignValue(valueNode, builder, scope);
varInfo.addRemovable(builder.buildNamedPropertyAssign(assignNode, propNameNode));
} else if (isDotPrototype(getPropLhs)) {
// objExpression.prototype.propertyName = someValue
Node objExpression = getPropLhs.getFirstChild();
RemovableBuilder builder = new RemovableBuilder().setIsPrototypeDotPropertyReference(true);
traverseRemovableAssignValue(valueNode, builder, scope);
if (objExpression.isName()) {
// varName.prototype.propertyName = someValue
VarInfo varInfo = traverseNameNode(getPropLhs.getFirstChild(), scope);
varInfo.addRemovable(builder.buildNamedPropertyAssign(assignNode, propNameNode));
} else {
// (someExpression).prototype.propertyName = someValue
if (NodeUtil.mayHaveSideEffects(objExpression)) {
traverseNode(objExpression, scope);
} else {
builder.addContinuation(new Continuation(objExpression, scope));
}
considerForIndependentRemoval(
builder.buildAnonymousPrototypeNamedPropertyAssign(
assignNode, propNameNode.getString()));
}
} else if (getPropLhs.isThis()) {
// this.propertyName = someValue
RemovableBuilder builder = new RemovableBuilder().setIsThisDotPropertyReference(true);
traverseRemovableAssignValue(valueNode, builder, scope);
considerForIndependentRemoval(builder.buildNamedPropertyAssign(assignNode, propNameNode));
} else {
traverseNode(lhs, scope);
traverseNode(valueNode, scope);
}
} else {
// no other cases are removable
traverseNode(lhs, scope);
traverseNode(valueNode, scope);
}
}
private void traverseRemovableAssignValue(Node valueNode, RemovableBuilder builder, Scope scope) {
if (NodeUtil.mayHaveSideEffects(valueNode)
|| NodeUtil.isExpressionResultUsed(valueNode.getParent())) {
traverseNode(valueNode, scope);
} else {
builder.addContinuation(new Continuation(valueNode, scope));
}
}
private boolean isNameDotPrototype(Node n) {
return n.isGetProp()
&& n.getFirstChild().isName()
&& n.getLastChild().getString().equals("prototype");
}
private void traverseDefaultValue(Node defaultValueNode, Scope scope) {
Node target = defaultValueNode.getFirstChild();
Node value = target.getNext();
if (NodeUtil.mayHaveSideEffects(value)) {
// TODO(bradfordcsmith): Preserve side effects without keeping unreferenced variables and
// properties alive.
traverseNode(target, scope);
traverseNode(value, scope);
} else if (target.isName()) {
VarInfo varInfo = traverseNameNode(target, scope);
DestructuringAssign assign =
new RemovableBuilder()
.addContinuation(new Continuation(value, scope))
.buildDestructuringAssign(target);
varInfo.addRemovable(assign);
} else if (isThisDotProperty(target)) {
DestructuringAssign assign =
new RemovableBuilder()
.addContinuation(new Continuation(value, scope))
.buildDestructuringAssign(target);
considerForIndependentRemoval(assign);
} else {
traverseNode(target, scope);
traverseNode(value, scope);
}
}
private void traverseArrayPattern(Node arrayPattern, Scope scope) {
for (Node c = arrayPattern.getFirstChild(); c != null; c = c.getNext()) {
if (c.isName()) {
VarInfo varInfo = traverseNameNode(c, scope);
varInfo.addRemovable(new RemovableBuilder().buildDestructuringAssign(c));
} else if (isThisDotProperty(c)) {
considerForIndependentRemoval(new RemovableBuilder().buildDestructuringAssign(c));
} else if (c.isDefaultValue()) {
// traverseDefaultValue() will create a removable if necessary
traverseDefaultValue(c, scope);
} else {
// TODO(bradfordcsmith): Treat destructuring assignments to properties as removable writes.
traverseNode(c, scope);
}
}
}
private void traverseObjectPattern(Node objectPattern, Scope scope) {
for (Node propertyNode = objectPattern.getFirstChild();
propertyNode != null;
propertyNode = propertyNode.getNext()) {
if (propertyNode.isComputedProp()) {
traverseObjectPatternComputedProperty(propertyNode, scope);
} else {
traverseObjectPatternStringKey(propertyNode, scope);
}
}
}
private void traverseObjectPatternStringKey(Node elm, Scope scope) {
checkArgument(elm.isStringKey(), elm);
// `{propertyName: target} = ...`
// or
// `{'propertyName': target} = ...`
// NOTE: The parser will convert `{1: x} = ...` to `{'1': x} = ...`
// TODO(bradfordcsmith): Avoid marking the property name as referenced until we know we won't
// remove the assignment.
if (!elm.isQuotedString()) {
markPropertyNameReferenced(elm.getString());
}
Node target = elm.getOnlyChild();
Node defaultValue = null;
if (target.isDefaultValue()) {
target = target.getFirstChild();
defaultValue = checkNotNull(target.getNext());
}
if (defaultValue != null && NodeUtil.mayHaveSideEffects(defaultValue)) {
// TODO(bradfordcsmith): Preserve side effects without preventing removal of variables and
// properties.
if (defaultValue != null) {
traverseNode(defaultValue, scope);
}
traverseNode(target, scope);
} else if (target.isName()) {
VarInfo varInfo = traverseNameNode(target, scope);
RemovableBuilder builder = new RemovableBuilder();
if (defaultValue != null) {
builder.addContinuation(new Continuation(defaultValue, scope));
}
varInfo.addRemovable(builder.buildDestructuringAssign(target));
} else if (isThisDotProperty(target)) {
RemovableBuilder builder = new RemovableBuilder();
if (defaultValue != null) {
builder.addContinuation(new Continuation(defaultValue, scope));
}
considerForIndependentRemoval(builder.buildDestructuringAssign(target));
} else {
// TODO(bradfordcsmith): Handle property assignments also
// e.g. `({a: foo.bar, b: foo.baz}) = {a: 1, b: 2}`
if (defaultValue != null) {
traverseNode(defaultValue, scope);
}
traverseNode(target, scope);
}
}
private void traverseObjectPatternComputedProperty(Node elm, Scope scope) {
// `{[propertyExpression]: target} = ...`
checkArgument(elm.isComputedProp(), elm);
Node propertyExpression = elm.getFirstChild();
Node target = propertyExpression.getNext();
Node defaultValue = null;
if (target.isDefaultValue()) {
target = target.getFirstChild();
defaultValue = checkNotNull(target.getNext());
}
if (NodeUtil.mayHaveSideEffects(propertyExpression)
|| (defaultValue != null && NodeUtil.mayHaveSideEffects(defaultValue))) {
// TODO(bradfordcsmith): Preserve side effects without preventing removal of variables and
// properties.
traverseNode(propertyExpression, scope);
if (defaultValue != null) {
traverseNode(defaultValue, scope);
}
traverseNode(target, scope);
} else if (target.isName()) {
VarInfo varInfo = traverseNameNode(target, scope);
RemovableBuilder builder = new RemovableBuilder();
builder.addContinuation(new Continuation(propertyExpression, scope));
if (defaultValue != null) {
builder.addContinuation(new Continuation(defaultValue, scope));
}
varInfo.addRemovable(builder.buildDestructuringAssign(target));
} else if (isNameDotPrototype(target)) {
RemovableBuilder builder = new RemovableBuilder();
builder.addContinuation(new Continuation(propertyExpression, scope));
if (defaultValue != null) {
builder.addContinuation(new Continuation(defaultValue, scope));
}
considerForIndependentRemoval(builder.buildDestructuringAssign(target));
} else {
// TODO(bradfordcsmith): Handle property assignments also
// e.g. `({a: foo.bar, b: foo.baz}) = {a: 1, b: 2}`
traverseNode(propertyExpression, scope);
if (defaultValue != null) {
traverseNode(defaultValue, scope);
}
traverseNode(target, scope);
}
}
private void traverseChildren(Node n, Scope scope) {
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
traverseNode(c, scope);
}
}
/**
* Handle a class that is not the RHS child of an assignment or a variable declaration
* initializer.
*
* For
* @param classNode
* @param scope
*/
private void traverseClass(Node classNode, Scope scope) {
checkArgument(classNode.isClass());
if (NodeUtil.isClassDeclaration(classNode)) {
traverseClassDeclaration(classNode, scope);
} else {
traverseClassExpression(classNode, scope);
}
}
private void traverseClassDeclaration(Node classNode, Scope scope) {
checkArgument(classNode.isClass());
Node classNameNode = classNode.getFirstChild();
Node baseClassExpression = classNameNode.getNext();
Node classBodyNode = baseClassExpression.getNext();
Scope classScope = scopeCreator.createScope(classNode, scope);
VarInfo varInfo = traverseNameNode(classNameNode, scope);
if (classNode.getParent().isExport()) {
// Cannot remove an exported class.
varInfo.setIsExplicitlyNotRemovable();
traverseNode(baseClassExpression, scope);
// Use traverseChildren() here, because we should not consider any properties on the exported
// class to be removable.
traverseChildren(classBodyNode, classScope);
} else if (NodeUtil.mayHaveSideEffects(baseClassExpression)) {
// TODO(bradfordcsmith): implement removal without losing side-effects for this case
varInfo.setIsExplicitlyNotRemovable();
traverseNode(baseClassExpression, scope);
traverseClassMembers(classBodyNode, classScope);
} else {
RemovableBuilder builder =
new RemovableBuilder()
.addContinuation(new Continuation(baseClassExpression, classScope))
.addContinuation(new Continuation(classBodyNode, classScope));
varInfo.addRemovable(builder.buildClassDeclaration(classNode));
}
}
private void traverseClassExpression(Node classNode, Scope scope) {
checkArgument(classNode.isClass());
Node classNameNode = classNode.getFirstChild();
Node baseClassExpression = classNameNode.getNext();
Node classBodyNode = baseClassExpression.getNext();
Scope classScope = scopeCreator.createScope(classNode, scope);
if (classNameNode.isName()) {
// We may be able to remove the name node if nothing ends up referring to it.
VarInfo varInfo = traverseNameNode(classNameNode, classScope);
varInfo.addRemovable(new RemovableBuilder().buildNamedClassExpression(classNode));
}
// If we're traversing the class expression, we've already decided we cannot remove it.
traverseNode(baseClassExpression, scope);
traverseClassMembers(classBodyNode, classScope);
}
private void traverseClassMembers(Node node, Scope scope) {
checkArgument(node.isClassMembers(), node);
if (removeUnusedPrototypeProperties) {
for (Node member = node.getFirstChild(); member != null; member = member.getNext()) {
if (member.isMemberFunctionDef() || NodeUtil.isGetOrSetKey(member)) {
// If we get as far as traversing the members of a class, we've already decided that
// we cannot remove the class itself, so just consider individual members for removal.
considerForIndependentRemoval(
new RemovableBuilder()
.addContinuation(new Continuation(member, scope))
.buildClassOrPrototypeNamedProperty(member));
} else {
checkState(member.isComputedProp());
traverseChildren(member, scope);
}
}
} else {
traverseChildren(node, scope);
}
}
/**
* Traverses a function
*
* ES6 scopes of a function include the parameter scope and the body scope
* of the function.
*
* Note that CATCH blocks also create a new scope, but only for the
* catch variable. Declarations within the block actually belong to the
* enclosing scope. Because we don't remove catch variables, there's
* no need to treat CATCH blocks differently like we do functions.
*/
private void traverseFunction(Node function, Scope parentScope) {
checkState(function.getChildCount() == 3, function);
checkState(function.isFunction(), function);
final Node paramlist = NodeUtil.getFunctionParameters(function);
final Node body = function.getLastChild();
checkState(body.getNext() == null && body.isNormalBlock(), body);
// Checking the parameters
Scope fparamScope = scopeCreator.createScope(function, parentScope);
// Checking the function body
Scope fbodyScope = scopeCreator.createScope(body, fparamScope);
Node nameNode = function.getFirstChild();
if (!nameNode.getString().isEmpty()) {
// var x = function funcName() {};
// make sure funcName gets into the varInfoMap so it will be considered for removal.
traverseNameNode(nameNode, fparamScope);
}
traverseChildren(paramlist, fparamScope);
traverseChildren(body, fbodyScope);
allFunctionParamScopes.add(fparamScope);
}
private boolean canRemoveParameters(Node parameterList) {
checkState(parameterList.isParamList());
Node function = parameterList.getParent();
return removeGlobals && !NodeUtil.isGetOrSetKey(function.getParent());
}
/**
* Removes unreferenced arguments from a function declaration and when
* possible the function's callSites.
*
* @param fparamScope The function parameter
*/
private void removeUnreferencedFunctionArgs(Scope fparamScope) {
// Notice that removing unreferenced function args breaks
// Function.prototype.length. In advanced mode, we don't really care
// about this: we consider "length" the equivalent of reflecting on
// the function's lexical source.
//
// Rather than create a new option for this, we assume that if the user
// is removing globals, then it's OK to remove unused function args.
//
// See http://blickly.github.io/closure-compiler-issues/#253
if (!removeGlobals) {
return;
}
Node function = fparamScope.getRootNode();
checkState(function.isFunction());
if (NodeUtil.isGetOrSetKey(function.getParent())) {
// The parameters object literal setters can not be removed.
return;
}
Node argList = NodeUtil.getFunctionParameters(function);
// Strip as many unreferenced args off the end of the function declaration as possible.
maybeRemoveUnusedTrailingParameters(argList, fparamScope);
// Mark any remaining unused parameters are unused to OptimizeParameters can try to remove
// them.
markUnusedParameters(argList, fparamScope);
}
private void markPropertyNameReferenced(String propertyName) {
if (referencedPropertyNames.add(propertyName)) {
// Continue traversal of all of the property name's values and no longer consider them for
// removal.
for (Removable removable : removablesForPropertyNames.removeAll(propertyName)) {
removable.applyContinuations();
}
}
}
private void considerForIndependentRemoval(Removable removable) {
if (removable.isNamedProperty()) {
String propertyName = removable.getPropertyName();
if (referencedPropertyNames.contains(propertyName)
|| codingConvention.isExported(propertyName)) {
// Referenced or exported, so not removable.
removable.applyContinuations();
} else if (isIndependentlyRemovable(removable)) {
// Store for possible removal later.
removablesForPropertyNames.put(propertyName, removable);
} else {
removable.applyContinuations();
// This assignment counts as a reference, since we won't be removing it.
// This is necessary in order to preserve getters and setters for the property.
markPropertyNameReferenced(propertyName);
}
} else {
removable.applyContinuations();
}
}
private boolean isIndependentlyRemovable(Removable removable) {
return (removeUnusedPrototypeProperties && removable.isPrototypeProperty())
|| (removeUnusedThisProperties && removable.isThisDotPropertyReference())
|| (removeUnusedObjectDefinePropertiesDefinitions
&& removable.isObjectDefinePropertiesDefinition())
|| (removeUnusedStaticProperties && removable.isStaticProperty());
}
/**
* Mark any remaining unused parameters as being unused so it can be used elsewhere.
*
* @param paramList list of function's parameters
* @param fparamScope
*/
private void markUnusedParameters(Node paramList, Scope fparamScope) {
for (Node param = paramList.getFirstChild(); param != null; param = param.getNext()) {
if (!param.isUnusedParameter()) {
Node lValue = param;
if (lValue.isDefaultValue()) {
lValue = lValue.getFirstChild();
}
if (lValue.isRest()) {
lValue = lValue.getOnlyChild();
}
if (lValue.isDestructuringPattern()) {
continue;
}
VarInfo varInfo = traverseNameNode(lValue, fparamScope);
if (varInfo.isRemovable()) {
param.setUnusedParameter(true);
compiler.reportChangeToEnclosingScope(paramList);
}
}
}
}
/**
* Strip as many unreferenced args off the end of the function declaration as possible. We start
* from the end of the function declaration because removing parameters from the middle of the
* param list could mess up the interpretation of parameters being sent over by any function
* calls.
*
* @param argList list of function's arguments
* @param fparamScope
*/
private void maybeRemoveUnusedTrailingParameters(Node argList, Scope fparamScope) {
Node lastArg;
while ((lastArg = argList.getLastChild()) != null) {
Node lValue = lastArg;
if (lastArg.isDefaultValue()) {
lValue = lastArg.getFirstChild();
if (NodeUtil.mayHaveSideEffects(lastArg.getLastChild())) {
break;
}
}
if (lValue.isRest()) {
lValue = lValue.getFirstChild();
}
if (lValue.isDestructuringPattern()) {
if (lValue.hasChildren()) {
// TODO(johnlenz): handle the case where there are no assignments.
break;
} else {
// Remove empty destructuring patterns and their associated object literal assignment
// if it exists and if the right hand side does not have side effects. Note, a
// destructuring pattern with a "leftover" property key as in {a:{}} is not considered
// empty in this case!
NodeUtil.deleteNode(lastArg, compiler);
continue;
}
}
VarInfo varInfo = getVarInfo(getVarForNameNode(lValue, fparamScope));
if (varInfo.isRemovable()) {
NodeUtil.deleteNode(lastArg, compiler);
} else {
break;
}
}
}
/**
* Handles a variable reference seen during traversal and returns a {@link VarInfo} object
* appropriate for the given {@link Var}.
*
*
This is a wrapper for {@link #getVarInfo} that handles additional logic needed when we're
* getting the {@link VarInfo} during traversal.
*/
private VarInfo traverseVar(Var var) {
checkNotNull(var);
if (removeLocalVars && var.isArguments()) {
// If we are considering removing local variables, that includes parameters.
// If `arguments` is used in a function we must consider all parameters to be referenced.
Scope functionScope = var.getScope().getClosestHoistScope();
Node paramList = NodeUtil.getFunctionParameters(functionScope.getRootNode());
for (Node param = paramList.getFirstChild(); param != null; param = param.getNext()) {
Node lValue = param;
if (lValue.isDefaultValue()) {
lValue = lValue.getFirstChild();
}
if (lValue.isRest()) {
lValue = lValue.getOnlyChild();
}
if (lValue.isDestructuringPattern()) {
continue;
}
getVarInfo(getVarForNameNode(lValue, functionScope)).markAsReferenced();
}
// `arguments` is never removable.
return canonicalUnremovableVarInfo;
} else {
return getVarInfo(var);
}
}
/**
* Get the right {@link VarInfo} object to use for the given {@link Var}.
*
*
This method is responsible for managing the entries in {@link #varInfoMap}.
*
Note: Several {@link Var}s may share the same {@link VarInfo} when they should be treated
* the same way.
*/
private VarInfo getVarInfo(Var var) {
checkNotNull(var);
boolean isGlobal = var.isGlobal();
if (var.isExtern()) {
return canonicalUnremovableVarInfo;
} else if (isGlobal && !removeGlobals) {
return canonicalUnremovableVarInfo;
} else if (!isGlobal && !removeLocalVars) {
return canonicalUnremovableVarInfo;
} else if (codingConvention.isExported(var.getName(), !isGlobal)) {
return canonicalUnremovableVarInfo;
} else if (var.isArguments()) {
return canonicalUnremovableVarInfo;
} else {
VarInfo varInfo = varInfoMap.get(var);
if (varInfo == null) {
varInfo = new VarInfo();
if (var.getParentNode().isParamList()) {
varInfo.hasNonLocalOrNonLiteralValue = true;
}
varInfoMap.put(var, varInfo);
}
return varInfo;
}
}
/**
* Removes any vars in the scope that were not referenced. Removes any assignments to those
* variables as well.
*/
private void removeUnreferencedVars() {
for (Entryentry : varInfoMap.entrySet()) {
Var var = entry.getKey();
VarInfo varInfo = entry.getValue();
if (!varInfo.isRemovable()) {
continue;
}
// Regardless of what happens to the original declaration,
// we need to remove all assigns, because they may contain references
// to other unreferenced variables.
varInfo.removeAllRemovables();
Node nameNode = var.nameNode;
Node toRemove = nameNode.getParent();
if (toRemove == null || alreadyRemoved(toRemove)) {
// assignedVarInfo.removeAllRemovables () already removed it
} else if (NodeUtil.isFunctionExpression(toRemove)) {
// TODO(bradfordcsmith): Add a Removable for this case.
if (!preserveFunctionExpressionNames) {
Node fnNameNode = toRemove.getFirstChild();
compiler.reportChangeToEnclosingScope(fnNameNode);
fnNameNode.setString("");
}
} else {
// Removables are not created for theses cases.
// function foo(unused1 = someSideEffectingValue, ...unused2) {}
// removeUnreferencedFunctionArgs() is responsible for removing these.
// TODO(bradfordcsmith): handle parameter declarations with removables
checkState(
toRemove.isParamList()
|| (toRemove.getParent().isParamList()
&& (toRemove.isDefaultValue() || toRemove.isRest())),
"unremoved code: %s",
toRemove);
}
}
}
/**
* Our progress in a traversal can be expressed completely as the
* current node and scope. The continuation lets us save that
* information so that we can continue the traversal later.
*/
private class Continuation {
private final Node node;
private final Scope scope;
Continuation(Node node, Scope scope) {
this.node = node;
this.scope = scope;
}
void apply() {
if (node.isFunction()) {
// Calling traverseNode here would create infinite recursion for a function declaration
traverseFunction(node, scope);
} else {
traverseNode(node, scope);
}
}
}
/** Represents a portion of the AST that can be removed. */
private abstract class Removable {
private final List continuations;
@Nullable private final String propertyName;
private final boolean isPrototypeDotPropertyReference;
private final boolean isThisDotPropertyReference;
private boolean continuationsAreApplied = false;
private boolean isRemoved = false;
Removable(RemovableBuilder builder) {
continuations = builder.continuations;
propertyName = builder.propertyName;
isPrototypeDotPropertyReference = builder.isPrototypeDotPropertyReference;
isThisDotPropertyReference = builder.isThisDotPropertyReference;
}
String getPropertyName() {
return checkNotNull(propertyName);
}
/** Remove the associated nodes from the AST. */
abstract void removeInternal(AbstractCompiler compiler);
/** Remove the associated nodes from the AST, unless they've already been removed. */
void remove(AbstractCompiler compiler) {
if (!isRemoved) {
isRemoved = true;
removeInternal(compiler);
}
}
public void applyContinuations() {
if (!continuationsAreApplied) {
continuationsAreApplied = true;
for (Continuation c : continuations) {
// Enqueue the continuation for processing.
// Don't invoke the continuation immediately, because that can lead to concurrent
// modification of data structures.
worklist.add(c);
}
continuations.clear();
}
}
/** True if this object represents assignment to a variable. */
boolean isVariableAssignment() {
return false;
}
/** True if this object represents a named property, either assignment or declaration. */
boolean isNamedProperty() {
return propertyName != null;
}
/**
* True if this object represents assignment to a named property.
*
* This does not include class or object literal member declarations.
*/
boolean isNamedPropertyAssignment() {
return false;
}
boolean isAssignedValueLocal() {
return false; // assume non-local by default
}
/** Is this a direct assignment to `varName.prototype`? */
boolean isPrototypeAssignment() {
return isNamedPropertyAssignment() && propertyName.equals("prototype");
}
/** Is this an assignment to a property on a prototype object? */
boolean isPrototypeDotPropertyReference() {
return isPrototypeDotPropertyReference;
}
boolean isClassOrPrototypeNamedProperty() {
return false;
}
boolean isPrototypeProperty() {
return isPrototypeDotPropertyReference() || isClassOrPrototypeNamedProperty();
}
boolean isThisDotPropertyReference() {
return isThisDotPropertyReference;
}
public boolean isObjectDefinePropertiesDefinition() {
return false;
}
public boolean isStaticProperty() {
return false;
}
/**
* Would a nonlocal or nonliteral value prevent removal of a variable associated with this
* {@link Removable}?
*
*
True if the nature of this removable is such that a variable associated with it must not
* be removed if its value or its prototype is not a local, literal value.
*
*
e.g. When X or X.prototype is nonlocal and / or nonliteral we don't know whether it is
* safe to remove code like this.
*
*
* X.propName = something; // Don't know the effect of setting X.propName
* use(something instanceof X); // can't be certain there are no instances of X
*
*/
public boolean preventsRemovalOfVariableWithNonLocalValueOrPrototype() {
return false;
}
}
private class RemovableBuilder {
final List continuations = new ArrayList<>();
@Nullable String propertyName = null;
boolean isPrototypeDotPropertyReference = false;
boolean isThisDotPropertyReference = false;
RemovableBuilder addContinuation(Continuation continuation) {
continuations.add(continuation);
return this;
}
RemovableBuilder setIsPrototypeDotPropertyReference(boolean value) {
this.isPrototypeDotPropertyReference = value;
return this;
}
RemovableBuilder setIsThisDotPropertyReference(boolean value) {
this.isThisDotPropertyReference = value;
return this;
}
DestructuringAssign buildDestructuringAssign(Node targetNode) {
return new DestructuringAssign(this, targetNode);
}
ClassDeclaration buildClassDeclaration(Node classNode) {
return new ClassDeclaration(this, classNode);
}
NamedClassExpression buildNamedClassExpression(Node classNode) {
return new NamedClassExpression(this, classNode);
}
ClassOrPrototypeNamedProperty buildClassOrPrototypeNamedProperty(Node propertyNode) {
checkArgument(
propertyNode.isMemberFunctionDef()
|| NodeUtil.isGetOrSetKey(propertyNode)
|| (propertyNode.isStringKey() && !propertyNode.isQuotedString()),
propertyNode);
this.propertyName = propertyNode.getString();
return new ClassOrPrototypeNamedProperty(this, propertyNode);
}
ObjectDefinePropertiesDefinition buildObjectDefinePropertiesDefinition(Node propertyNode) {
this.propertyName = propertyNode.getString();
return new ObjectDefinePropertiesDefinition(this, propertyNode);
}
FunctionDeclaration buildFunctionDeclaration(Node functionNode) {
return new FunctionDeclaration(this, functionNode);
}
NameDeclarationStatement buildNameDeclarationStatement(Node declarationStatement) {
return new NameDeclarationStatement(this, declarationStatement);
}
Assign buildNamedPropertyAssign(Node assignNode, Node propertyNode) {
this.propertyName = propertyNode.getString();
return new Assign(this, assignNode, Kind.NAMED_PROPERTY, propertyNode);
}
Assign buildComputedPropertyAssign(Node assignNode, Node propertyNode) {
return new Assign(this, assignNode, Kind.COMPUTED_PROPERTY, propertyNode);
}
Assign buildVariableAssign(Node assignNode) {
return new Assign(this, assignNode, Kind.VARIABLE, /* propertyNode */ null);
}
ClassSetupCall buildClassSetupCall(Node callNode) {
return new ClassSetupCall(this, callNode);
}
VanillaForNameDeclaration buildVanillaForNameDeclaration(Node nameNode) {
return new VanillaForNameDeclaration(this, nameNode);
}
AnonymousPrototypeNamedPropertyAssign buildAnonymousPrototypeNamedPropertyAssign(
Node assignNode, String propertyName) {
this.propertyName = propertyName;
return new AnonymousPrototypeNamedPropertyAssign(this, assignNode);
}
IncOrDecOp buildIncOrDepOp(Node incOrDecOp, Node propertyNode) {
this.propertyName = propertyNode.getString();
return new IncOrDecOp(this, incOrDecOp);
}
UnusedReadReference buildUnusedReadReference(Node referenceNode, Node propertyNode) {
this.propertyName = propertyNode.getString();
return new UnusedReadReference(this, referenceNode);
}
public Removable buildInstanceofName(Node instanceofNode) {
return new InstanceofName(this, instanceofNode);
}
}
/** Represents a read reference whose value is not used. */
private class UnusedReadReference extends Removable {
final Node referenceNode;
UnusedReadReference(RemovableBuilder builder, Node referenceNode) {
super(builder);
// TODO(bradfordcsmith): handle `name;` and `name.property;` references
checkState(
isThisDotProperty(referenceNode) || isDotPrototypeDotProperty(referenceNode),
referenceNode);
this.referenceNode = referenceNode;
}
@Override
void removeInternal(AbstractCompiler compiler) {
if (!alreadyRemoved(referenceNode)) {
if (isThisDotProperty(referenceNode)) {
removeExpressionCompletely(referenceNode);
} else {
checkState(isDotPrototypeDotProperty(referenceNode), referenceNode);
// objExpression.prototype.propertyName
Node objExpression = referenceNode.getFirstFirstChild();
if (NodeUtil.mayHaveSideEffects(objExpression)) {
replaceNodeWith(referenceNode, objExpression.detach());
} else {
removeExpressionCompletely(referenceNode);
}
}
}
}
}
/**
* Represents `something instanceof varName`.
*
* If `varName` is removed, this expression can be replaced with `false` or
* `(something, false)` to preserve side effects.
*/
private class InstanceofName extends Removable {
final Node instanceofNode;
InstanceofName(RemovableBuilder builder, Node instanceofNode) {
super(builder);
checkArgument(instanceofNode.isInstanceOf(), instanceofNode);
this.instanceofNode = instanceofNode;
}
@Override
void removeInternal(AbstractCompiler compiler) {
if (!alreadyRemoved(instanceofNode)) {
Node lhs = instanceofNode.getFirstChild();
Node falseNode = IR.falseNode().srcref(instanceofNode);
if (NodeUtil.mayHaveSideEffects(lhs)) {
replaceNodeWith(instanceofNode, IR.comma(lhs.detach(), falseNode).srcref(instanceofNode));
} else {
replaceNodeWith(instanceofNode, falseNode);
}
}
}
@Override
public boolean preventsRemovalOfVariableWithNonLocalValueOrPrototype() {
// If we aren't sure where X comes from and what aliases it might have, we cannot be sure
// there are no instances of it.
return true;
}
}
/** Represents an increment or decrement operation that could be removed. */
private class IncOrDecOp extends Removable {
final Node incOrDecNode;
IncOrDecOp(RemovableBuilder builder, Node incOrDecNode) {
super(builder);
checkArgument(incOrDecNode.isInc() || incOrDecNode.isDec(), incOrDecNode);
Node arg = incOrDecNode.getOnlyChild();
// TODO(bradfordcsmith): handle `name;` and `name.property;` references
checkState(isThisDotProperty(arg) || isDotPrototypeDotProperty(arg), arg);
this.incOrDecNode = incOrDecNode;
}
@Override
void removeInternal(AbstractCompiler compiler) {
if (!alreadyRemoved(incOrDecNode)) {
Node arg = incOrDecNode.getOnlyChild();
checkState(arg.isGetProp(), arg);
if (isThisDotProperty(arg)) {
removeExpressionCompletely(incOrDecNode);
} else {
checkState(isDotPrototypeDotProperty(arg), arg);
// objExpression.prototype.propertyName
Node objExpression = arg.getFirstFirstChild();
if (NodeUtil.mayHaveSideEffects(objExpression)) {
replaceNodeWith(incOrDecNode, objExpression.detach());
} else {
removeExpressionCompletely(incOrDecNode);
}
}
}
}
}
/** True for `this.propertyName` */
private static boolean isThisDotProperty(Node n) {
return n.isGetProp() && n.getFirstChild().isThis();
}
/** True for `(something).prototype.propertyName` */
private static boolean isDotPrototypeDotProperty(Node n) {
return n.isGetProp() && isDotPrototype(n.getFirstChild());
}
private class DestructuringAssign extends Removable {
final Node targetNode;
DestructuringAssign(RemovableBuilder builder, Node targetNode) {
super(builder);
checkState(targetNode.isName() || isThisDotProperty(targetNode), targetNode);
this.targetNode = targetNode;
}
@Override
boolean isVariableAssignment() {
return targetNode.isName();
}
@Override
boolean isThisDotPropertyReference() {
return isThisDotProperty(targetNode);
}
@Override
boolean isNamedProperty() {
return targetNode.isGetProp();
}
@Override
public boolean preventsRemovalOfVariableWithNonLocalValueOrPrototype() {
if (targetNode.isGetProp()) {
Node getPropLhs = targetNode.getFirstChild();
// assignment to varName.property or varName.prototype.property
// cannot be removed unless varName and varName.prototype have literal, local values.
return getPropLhs.isName() || isNameDotPrototype(getPropLhs);
} else {
return false;
}
}
@Override
boolean isNamedPropertyAssignment() {
return targetNode.isGetProp();
}
@Override
String getPropertyName() {
checkState(targetNode.isGetProp(), targetNode);
return targetNode.getLastChild().getString();
}
@Override
public void removeInternal(AbstractCompiler compiler) {
if (!alreadyRemoved(targetNode)) {
removeDestructuringTarget(targetNode);
}
}
private void removeDestructuringTarget(Node target) {
Node targetParent = target.getParent();
if (targetParent.isArrayPattern()) {
// [a, target, b] = something;
// [a, target] = something;
// Replace target with an empty node to avoid messing up the order of patterns,
// then clean up trailing empties.
replaceNodeWith(target, IR.empty().srcref(target));
// We prefer `[a, b]` to `[a, b, , , , ]`
// So remove any trailing empty nodes.
for (Node maybeEmpty = targetParent.getLastChild();
maybeEmpty != null && maybeEmpty.isEmpty();
maybeEmpty = targetParent.getLastChild()) {
maybeEmpty.detach();
}
compiler.reportChangeToEnclosingScope(targetParent);
// TODO(bradfordcsmith): If the array pattern is now empty, try to remove it entirely.
} else if (targetParent.isParamList()) {
// removeUnreferencedFunctionArgs() is responsible for removal of function parameter
// positions, so all we can do here is remove the default value.
// NOTE: traverseRest() avoids creating a removable for a rest parameter.
// TODO(bradfordcsmith): Handle parameter removal consistently with other removals.
checkState(target.isDefaultValue(), target);
// function(removableName = removableValue)
compiler.reportChangeToEnclosingScope(targetParent);
// preserve the slot in the parameter list
Node name = target.getFirstChild();
checkState(name.isName());
if (target == targetParent.getLastChild()
&& removeGlobals
&& canRemoveParameters(targetParent)) {
// function(p1, removableName = removableDefault)
// and we're allowed to remove the parameter entirely
target.detach();
} else {
// function(removableName = removableDefault, otherParam)
// or removableName is at the end, but cannot be completely removed.
target.replaceWith(name.detach());
}
NodeUtil.markFunctionsDeleted(target, compiler);
} else if (targetParent.isRest()) {
// remove all of `...target`
removeDestructuringTarget(targetParent);
} else if (targetParent.isDefaultValue()) {
// remove value along with target
removeDestructuringTarget(targetParent);
} else {
// ({ [propExpression]: target } = something)
// becomes
// ({} = something)
checkState(targetParent.isStringKey() || targetParent.isComputedProp(), targetParent);
NodeUtil.deleteNode(targetParent, compiler);
// TODO(bradfordcsmith): If the pattern is now empty, see if it can be removed.
}
}
}
private class ClassDeclaration extends Removable {
final Node classDeclarationNode;
ClassDeclaration(RemovableBuilder builder, Node classDeclarationNode) {
super(builder);
this.classDeclarationNode = classDeclarationNode;
}
@Override
public void removeInternal(AbstractCompiler compiler) {
NodeUtil.deleteNode(classDeclarationNode, compiler);
}
}
private class NamedClassExpression extends Removable {
final Node classNode;
NamedClassExpression(RemovableBuilder builder, Node classNode) {
super(builder);
this.classNode = classNode;
}
@Override
public void removeInternal(AbstractCompiler compiler) {
if (!alreadyRemoved(classNode)) {
Node nameNode = classNode.getFirstChild();
if (!nameNode.isEmpty()) {
// Just empty the class's name. If the expression is assigned to an unused variable,
// then the whole class might still be removed as part of that assignment.
classNode.replaceChild(nameNode, IR.empty().useSourceInfoFrom(nameNode));
compiler.reportChangeToEnclosingScope(classNode);
}
}
}
}
private class ClassOrPrototypeNamedProperty extends Removable {
final Node propertyNode;
ClassOrPrototypeNamedProperty(RemovableBuilder builder, Node propertyNode) {
super(builder);
this.propertyNode = propertyNode;
}
@Override
public boolean isStaticProperty() {
return propertyNode.isStaticMember();
}
@Override
boolean isClassOrPrototypeNamedProperty() {
return !isStaticProperty();
}
@Override
void removeInternal(AbstractCompiler compiler) {
NodeUtil.deleteNode(propertyNode, compiler);
}
}
/**
* Represents a single property definition in the object literal passed as the second argument to
* e.g. `Object.defineProperties(obj, {p1: {value: 1}, p2: {value: 3}});`.
*/
private class ObjectDefinePropertiesDefinition extends Removable {
final Node propertyNode;
ObjectDefinePropertiesDefinition(RemovableBuilder builder, Node propertyNode) {
super(builder);
this.propertyNode = propertyNode;
}
@Override
public boolean isObjectDefinePropertiesDefinition() {
return true;
}
@Override
void removeInternal(AbstractCompiler compiler) {
NodeUtil.deleteNode(propertyNode, compiler);
}
}
private class FunctionDeclaration extends Removable {
final Node functionDeclarationNode;
FunctionDeclaration(RemovableBuilder builder, Node functionDeclarationNode) {
super(builder);
this.functionDeclarationNode = functionDeclarationNode;
}
@Override
public void removeInternal(AbstractCompiler compiler) {
NodeUtil.deleteNode(functionDeclarationNode, compiler);
}
@Override
boolean isAssignedValueLocal() {
// The declared function is always created locally.
return true;
}
}
private class NameDeclarationStatement extends Removable {
private final Node declarationStatement;
public NameDeclarationStatement(RemovableBuilder builder, Node declarationStatement) {
super(builder);
checkArgument(NodeUtil.isNameDeclaration(declarationStatement), declarationStatement);
this.declarationStatement = declarationStatement;
}
@Override
void removeInternal(AbstractCompiler compiler) {
Node nameNode = declarationStatement.getOnlyChild();
Node valueNode = nameNode.getFirstChild();
if (valueNode != null && NodeUtil.mayHaveSideEffects(valueNode)) {
compiler.reportChangeToEnclosingScope(declarationStatement);
valueNode.detach();
declarationStatement.replaceWith(IR.exprResult(valueNode).useSourceInfoFrom(valueNode));
} else {
NodeUtil.deleteNode(declarationStatement, compiler);
}
}
@Override
boolean isVariableAssignment() {
return true;
}
@Override
boolean isAssignedValueLocal() {
Node nameNode = declarationStatement.getOnlyChild();
Node valueNode = nameNode.getFirstChild();
return valueNode == null
|| isLocalDefaultValueAssignment(nameNode, valueNode)
|| NodeUtil.evaluatesToLocalValue(valueNode);
}
@Override
public String toString() {
return "NameDeclStmt:" + declarationStatement;
}
}
/**
* True if targetNode is a qualified name and the valueNode is of the form `targetQualifiedName ||
* localValue`.
*/
private static boolean isLocalDefaultValueAssignment(Node targetNode, Node valueNode) {
return valueNode.isOr()
&& targetNode.isQualifiedName()
&& valueNode.getFirstChild().isEquivalentTo(targetNode)
&& NodeUtil.evaluatesToLocalValue(valueNode.getLastChild());
}
enum Kind {
// X = something;
VARIABLE,
// X.propertyName = something;
// X.prototype.propertyName = something;
NAMED_PROPERTY,
// X[expression] = something;
// X.prototype[expression] = something;
COMPUTED_PROPERTY;
}
private class Assign extends Removable {
final Node assignNode;
final Kind kind;
Assign(
RemovableBuilder builder,
Node assignNode,
Kind kind,
@Nullable Node propertyNode) {
super(builder);
checkArgument(NodeUtil.isAssignmentOp(assignNode), assignNode);
if (kind == Kind.VARIABLE) {
checkArgument(
propertyNode == null,
"got property node for simple variable assignment: %s",
propertyNode);
} else {
checkArgument(propertyNode != null, "missing property node");
if (kind == Kind.NAMED_PROPERTY) {
checkArgument(propertyNode.isString(), "property name is not a string: %s", propertyNode);
}
}
this.assignNode = assignNode;
this.kind = kind;
}
/** True for `varName = value` assignments. */
@Override
boolean isVariableAssignment() {
return kind == Kind.VARIABLE;
}
@Override
boolean isAssignedValueLocal() {
if (NodeUtil.isExpressionResultUsed(assignNode)) {
// assigned value may escape or be aliased
return false;
} else {
Node targetNode = assignNode.getFirstChild();
Node valueNode = targetNode.getNext();
return NodeUtil.evaluatesToLocalValue(valueNode)
|| isLocalDefaultValueAssignment(targetNode, valueNode);
}
}
@Override
public boolean preventsRemovalOfVariableWithNonLocalValueOrPrototype() {
// If we don't know where the variable comes from or where it may go, then we don't know
// whether it is safe to remove assignments to properties on it.
return isNamedPropertyAssignment() || isComputedPropertyAssignment();
}
/** True for `varName.propName = value` and `varName.prototype.propName = value` assignments. */
@Override
boolean isNamedPropertyAssignment() {
return kind == Kind.NAMED_PROPERTY;
}
/** True for `varName[expr] = value` and `varName.prototype[expr] = value` assignments. */
boolean isComputedPropertyAssignment() {
return kind == Kind.COMPUTED_PROPERTY;
}
@Override
public boolean isStaticProperty() {
Node lhs = assignNode.getFirstChild();
if (lhs.isGetProp()) {
// something.propName = someValue
Node getPropLhs = lhs.getFirstChild();
TypeI typeI = getPropLhs.getTypeI();
return typeI != null && (typeI.isConstructor() || typeI.isInterface());
} else {
return false;
}
}
/** Replace the current assign with its right hand side. */
@Override
public void removeInternal(AbstractCompiler compiler) {
if (alreadyRemoved(assignNode)) {
return;
}
Node parent = assignNode.getParent();
compiler.reportChangeToEnclosingScope(parent);
Node lhs = assignNode.getFirstChild();
Node rhs = assignNode.getSecondChild();
boolean mustPreserveRhs =
NodeUtil.mayHaveSideEffects(rhs) || NodeUtil.isExpressionResultUsed(assignNode);
boolean mustPreserveGetElmExpr =
lhs.isGetElem() && NodeUtil.mayHaveSideEffects(lhs.getLastChild());
if (mustPreserveRhs && mustPreserveGetElmExpr) {
Node replacement =
IR.comma(lhs.getLastChild().detach(), rhs.detach()).useSourceInfoFrom(assignNode);
replaceNodeWith(assignNode, replacement);
} else if (mustPreserveGetElmExpr) {
replaceNodeWith(assignNode, lhs.getLastChild().detach());
} else if (mustPreserveRhs) {
replaceNodeWith(assignNode, rhs.detach());
} else {
removeExpressionCompletely(assignNode);
}
}
@Override
public String toString() {
return "Assign:" + assignNode;
}
}
/** Represents `(someObjectExpression).prototype.propertyName = someValue`. */
private class AnonymousPrototypeNamedPropertyAssign extends Removable {
final Node assignNode;
AnonymousPrototypeNamedPropertyAssign(RemovableBuilder builder, Node assignNode) {
super(builder);
checkNotNull(builder.propertyName);
checkArgument(assignNode.isAssign(), assignNode);
this.assignNode = assignNode;
}
@Override
void removeInternal(AbstractCompiler compiler) {
if (alreadyRemoved(assignNode)) {
return;
}
Node parent = assignNode.getParent();
compiler.reportChangeToEnclosingScope(parent);
Node lhs = assignNode.getFirstChild();
Node rhs = assignNode.getLastChild();
checkState(lhs.isGetProp(), lhs);
Node objDotPrototype = lhs.getFirstChild();
checkState(objDotPrototype.isGetProp(), objDotPrototype);
Node objExpression = objDotPrototype.getFirstChild();
Node prototype = objDotPrototype.getLastChild();
checkState(prototype.getString().equals("prototype"), prototype);
boolean mustPreserveRhs =
NodeUtil.mayHaveSideEffects(rhs) || NodeUtil.isExpressionResultUsed(assignNode);
boolean mustPreserveObjExpression = NodeUtil.mayHaveSideEffects(objExpression);
if (mustPreserveRhs && mustPreserveObjExpression) {
Node replacement =
IR.comma(objExpression.detach(), rhs.detach()).useSourceInfoFrom(assignNode);
replaceNodeWith(assignNode, replacement);
} else if (mustPreserveObjExpression) {
replaceNodeWith(assignNode, objExpression.detach());
} else if (mustPreserveRhs) {
replaceNodeWith(assignNode, rhs.detach());
} else {
removeExpressionCompletely(assignNode);
}
}
@Override
boolean isPrototypeProperty() {
return true;
}
}
/**
* Represents a call to a class setup method such as `goog.inherits()` or
* `goog.addSingletonGetter()`.
*/
private class ClassSetupCall extends Removable {
final Node callNode;
ClassSetupCall(RemovableBuilder builder, Node callNode) {
super(builder);
this.callNode = callNode;
}
@Override
public void removeInternal(AbstractCompiler compiler) {
Node parent = callNode.getParent();
Node replacement = null;
// Need to keep call args that have side effects.
// Easiest thing to do is break apart the call node as we go.
// First child is the callee (aka. Object.defineProperties or equivalent)
callNode.removeFirstChild();
for (Node arg = callNode.getLastChild(); arg != null; arg = callNode.getLastChild()) {
arg.detach();
if (NodeUtil.mayHaveSideEffects(arg)) {
if (replacement == null) {
replacement = arg;
} else {
replacement = IR.comma(arg, replacement).srcref(callNode);
}
} else {
NodeUtil.markFunctionsDeleted(arg, compiler);
}
}
// NOTE: The call must either be its own statement or the LHS of a comma expression,
// because it doesn't have a meaningful return value.
if (replacement != null) {
replaceNodeWith(callNode, replacement);
} else if (parent.isExprResult()) {
NodeUtil.deleteNode(parent, compiler);
} else {
// `(goog.inherits(A, B), something)` -> `something`
checkState(parent.isComma());
Node rhs = checkNotNull(callNode.getNext());
compiler.reportChangeToEnclosingScope(parent);
parent.replaceWith(rhs.detach());
}
}
@Override
public boolean preventsRemovalOfVariableWithNonLocalValueOrPrototype() {
// If we aren't sure where X comes from and what aliases it might have, we cannot be sure
// it's safe to remove the class setup for it.
return true;
}
}
private static boolean alreadyRemoved(Node n) {
Node parent = n.getParent();
if (parent == null) {
return true;
}
if (parent.isRoot()) {
return false;
}
return alreadyRemoved(parent);
}
private class VarInfo {
/**
* Objects that represent variable declarations, assignments, or class setup calls that can
* be removed.
*
* NOTE: Once we realize that we cannot remove the variable, this list will be cleared and
* no more will be added.
*/
final List removables = new ArrayList<>();
boolean isEntirelyRemovable = true;
boolean hasNonLocalOrNonLiteralValue = false;
boolean requiresLocalLiteralValueForRemoval = false;
void addRemovable(Removable removable) {
if (!removable.isAssignedValueLocal()
&& (removable.isVariableAssignment() || removable.isPrototypeAssignment())) {
hasNonLocalOrNonLiteralValue = true;
}
if (removable.preventsRemovalOfVariableWithNonLocalValueOrPrototype()) {
requiresLocalLiteralValueForRemoval = true;
}
if (hasNonLocalOrNonLiteralValue && requiresLocalLiteralValueForRemoval) {
setIsExplicitlyNotRemovable();
}
if (isEntirelyRemovable) {
// Store for possible removal later.
removables.add(removable);
} else {
considerForIndependentRemoval(removable);
}
}
/**
* Marks this variable as referenced and evaluates any continuations if not previously marked as
* referenced.
*
* @return true if the variable was not already marked as referenced
*/
boolean markAsReferenced() {
return setIsExplicitlyNotRemovable();
}
boolean isRemovable() {
return isEntirelyRemovable;
}
boolean setIsExplicitlyNotRemovable() {
if (isEntirelyRemovable) {
isEntirelyRemovable = false;
for (Removable r : removables) {
considerForIndependentRemoval(r);
}
removables.clear();
return true;
} else {
return false;
}
}
void removeAllRemovables() {
checkState(isEntirelyRemovable);
for (Removable removable : removables) {
removable.remove(compiler);
}
removables.clear();
}
}
/**
* Represents declarations in the standard for-loop initialization.
*
* e.g. the `let i = 0` part of `for (let i = 0; i < 10; ++i) {...}`.
* These must be handled differently from declaration statements because:
*
*
* -
* For-loop declarations may declare more than one variable.
* The normalization doesn't break them up as it does for declaration statements.
*
* -
* Removal must be handled differently.
*
* -
* We don't currently preserve initializers with side effects here.
* Instead, we just consider such cases non-removable.
*
*
*/
private class VanillaForNameDeclaration extends Removable {
private final Node nameNode;
private VanillaForNameDeclaration(RemovableBuilder builder, Node nameNode) {
super(builder);
this.nameNode = nameNode;
}
@Override
void removeInternal(AbstractCompiler compiler) {
Node declaration = checkNotNull(nameNode.getParent());
compiler.reportChangeToEnclosingScope(declaration);
// NOTE: We don't need to preserve the initializer value, because we currently do not remove
// for-loop vars whose initializing values have side effects.
if (nameNode.getPrevious() == null && nameNode.getNext() == null) {
// only child, so we can remove the whole declaration
declaration.replaceWith(IR.empty().useSourceInfoFrom(declaration));
} else {
declaration.removeChild(nameNode);
}
NodeUtil.markFunctionsDeleted(nameNode, compiler);
}
}
void removeExpressionCompletely(Node expression) {
checkState(!NodeUtil.isExpressionResultUsed(expression), expression);
Node parent = expression.getParent();
if (parent.isExprResult()) {
NodeUtil.deleteNode(parent, compiler);
} else if (parent.isComma()) {
// Expression is probably the first child of the comma,
// but it could be the second if the entire comma expression value is unused.
Node otherChild = expression.getNext();
if (otherChild == null) {
otherChild = expression.getPrevious();
}
replaceNodeWith(parent, otherChild.detach());
} else {
// value isn't needed, but we need to keep the AST valid.
replaceNodeWith(expression, IR.number(0).useSourceInfoFrom(expression));
}
}
void replaceNodeWith(Node n, Node replacement) {
compiler.reportChangeToEnclosingScope(n);
n.replaceWith(replacement);
NodeUtil.markFunctionsDeleted(n, compiler);
}
}