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/*
* Copyright 2017 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.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;
import com.google.javascript.jscomp.NodeTraversal.ScopedCallback;
import com.google.javascript.rhino.Node;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import javax.annotation.Nullable;
/** Collects global variable references for use by {@link CrossChunkCodeMotion}. */
public final class CrossChunkReferenceCollector implements ScopedCallback, CompilerPass {
/** Maps global variable name to the corresponding {@link Var} object. */
private final Map varsByName = new HashMap<>();
/**
* Maps a given variable to a collection of references to that name. Note that
* Var objects are not stable across multiple traversals (unlike scope root or
* name).
*/
private final Map referenceMap =
new LinkedHashMap<>();
/** The stack of basic blocks and scopes the current traversal is in. */
private final List blockStack = new ArrayList<>();
/** List of all top-level statements in the order they appear in the AST. */
private final List topLevelStatements = new ArrayList<>();
private final ScopeCreator scopeCreator;
/**
* JavaScript compiler to use in traversing.
*/
private final AbstractCompiler compiler;
private int statementCounter = 0;
private TopLevelStatementDraft topLevelStatementDraft = null;
/** Constructor initializes block stack. */
CrossChunkReferenceCollector(AbstractCompiler compiler, ScopeCreator creator) {
this.compiler = compiler;
this.scopeCreator = creator;
}
/**
* Convenience method for running this pass over a tree with this
* class as a callback.
*/
@Override
public void process(Node externs, Node root) {
checkState(topLevelStatements.isEmpty(), "process() called more than once");
NodeTraversal t = new NodeTraversal(compiler, this, scopeCreator);
t.traverseRoots(externs, root);
}
public void process(Node root) {
checkState(topLevelStatements.isEmpty(), "process() called more than once");
NodeTraversal t = new NodeTraversal(compiler, this, scopeCreator);
t.traverse(root);
}
/**
* Gets the variables that were referenced in this callback.
*/
Iterable getAllSymbols() {
return referenceMap.keySet();
}
/**
* Gets the reference collection for the given variable.
*/
ReferenceCollection getReferences(Var v) {
return referenceMap.get(v);
}
ImmutableMap getGlobalVariableNamesMap() {
return ImmutableMap.copyOf(varsByName);
}
/**
* For each node, update the block stack and reference collection
* as appropriate.
*/
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (topLevelStatementDraft != null) {
if (n.equals(topLevelStatementDraft.statementNode)) {
topLevelStatements.add(new TopLevelStatement(topLevelStatementDraft));
topLevelStatementDraft = null;
} else if (n.isName()) {
String varName = n.getString();
Var v = t.getScope().getVar(varName);
if (v != null) {
// Only global, non-exported names can be moved
if (v.isGlobal() && !compiler.getCodingConvention().isExported(v.getName())) {
if (varsByName.containsKey(varName)) {
checkState(Objects.equals(varsByName.get(varName), v));
} else {
varsByName.put(varName, v);
}
Reference reference = new Reference(n, t, peek(blockStack));
if (reference.getNode() == topLevelStatementDraft.declaredNameNode) {
topLevelStatementDraft.declaredNameReference = reference;
} else {
topLevelStatementDraft.nonDeclarationReferences.add(reference);
}
addReferenceToCollection(v, reference);
}
}
}
}
if (isBlockBoundary(n, parent)) {
pop(blockStack);
}
}
/**
* Updates block stack and invokes any additional behavior.
*/
@Override
public void enterScope(NodeTraversal t) {
Node n = t.getScopeRoot();
BasicBlock parent = blockStack.isEmpty() ? null : peek(blockStack);
// Don't add all ES6 scope roots to blockStack, only those that are also scopes according to
// the ES5 scoping rules. Other nodes that ought to be considered the root of a BasicBlock
// are added in shouldTraverse() and removed in visit().
if (t.isHoistScope()) {
blockStack.add(new BasicBlock(parent, n));
}
}
/**
* Updates block stack and invokes any additional behavior.
*/
@Override
public void exitScope(NodeTraversal t) {
if (t.isHoistScope()) {
pop(blockStack);
}
}
@Override
public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent) {
if (parent != null && NodeUtil.isTopLevel(parent)) {
checkState(topLevelStatementDraft == null, n);
topLevelStatementDraft = initializeDraftStatement(nodeTraversal.getModule(), n);
}
// If node is a new basic block, put on basic block stack
if (isBlockBoundary(n, parent)) {
blockStack.add(new BasicBlock(peek(blockStack), n));
}
return true;
}
private TopLevelStatementDraft initializeDraftStatement(JSModule module, Node statementNode) {
TopLevelStatementDraft draft =
new TopLevelStatementDraft(statementCounter++, module, statementNode);
// Determine whether this statement declares a name or not.
// If so, save its name node and value node, if any.
if (NodeUtil.isNameDeclaration(statementNode)) {
// variable declaration
draft.declaredNameNode = statementNode.getFirstChild();
draft.declaredValueNode = statementNode.getFirstFirstChild();
} else if (statementNode.isClass()) {
draft.declaredNameNode = statementNode.getFirstChild();
draft.declaredValueNode = statementNode;
} else if (statementNode.isFunction()) {
// function declaration
draft.declaredNameNode = statementNode.getFirstChild();
draft.declaredValueNode = statementNode;
} else if (statementNode.isExprResult()) {
Node expr = checkNotNull(statementNode.getFirstChild());
if (expr.isAssign()) {
Node lhs = checkNotNull(expr.getFirstChild());
Node rhs = checkNotNull(expr.getSecondChild());
if (lhs.isName()) {
// `varName = value;`
draft.declaredNameNode = lhs;
draft.declaredValueNode = rhs;
} else if (lhs.isGetProp()) {
Node nameNode = checkNotNull(lhs.getFirstChild());
while (nameNode.isGetProp()) {
nameNode = checkNotNull(nameNode.getFirstChild());
}
if (nameNode.isName()) {
// `varName.some.property = value;`
draft.declaredNameNode = nameNode;
draft.declaredValueNode = rhs;
}
}
} else if (expr.isCall()) {
Node nameNode = null;
Node valueNode = null;
CodingConvention.SubclassRelationship relationship =
compiler.getCodingConvention().getClassesDefinedByCall(expr);
if (relationship != null) {
// Check for $jscomp.inherits(SubC, SuperC), goog.inherits(Sub, SuperC), etc.
String declaredName = checkNotNull(relationship.subclassName);
for (Node callArg = expr.getSecondChild(); callArg != null; callArg = callArg.getNext()) {
// We're assuming that the child class must be an argument to the function that
// establishes its inheritance, which is true for `goog.inherits()` and
// `$jscomp.inherits()`
// TODO(bradfordcsmith): handle cases like `goog.inherits(x.ChildClass, SuperClass)`
if (callArg.isName() && declaredName.equals(callArg.getString())) {
nameNode = callArg;
break;
}
}
} else if (NodeUtil.isObjectDefinePropertiesDefinition(expr)) {
// Check for $jscomp$global.Object.defineProperties.
Node targetObject = expr.getSecondChild();
// Get the global var being referenced in the first parameter of Object.defineProperties.
// Can be 'Foo' or 'Foo.prototype'.
nameNode = targetObject.isName() ? targetObject : targetObject.getFirstChild();
// Second parameter of defineProperties is the value node.
valueNode = targetObject.getNext();
}
if (nameNode != null) {
draft.declaredNameNode = nameNode;
draft.declaredValueNode = valueNode;
}
}
}
return draft;
}
private static T pop(List list) {
return list.remove(list.size() - 1);
}
private static T peek(List list) {
return Iterables.getLast(list);
}
/**
* @return true if this node marks the start of a new basic block
*/
private static boolean isBlockBoundary(Node n, Node parent) {
if (parent != null) {
switch (parent.getToken()) {
case DO:
case FOR:
case FOR_IN:
case FOR_OF:
case FOR_AWAIT_OF:
case TRY:
case WHILE:
case WITH:
case CLASS:
// NOTE: TRY has up to 3 child blocks:
// TRY
// BLOCK
// BLOCK
// CATCH
// BLOCK
// Note that there is an explicit CATCH token but no explicit
// FINALLY token. For simplicity, we consider each BLOCK
// a separate basic BLOCK.
return true;
case AND:
case HOOK:
case IF:
case OR:
case SWITCH:
case COALESCE:
// The first child of a conditional is not a boundary,
// but all the rest of the children are.
return n != parent.getFirstChild();
default:
break;
}
}
return n.isCase();
}
private void addReferenceToCollection(Var v, Reference reference) {
// Create collection if none already
ReferenceCollection referenceInfo =
referenceMap.computeIfAbsent(v, (Var k) -> new ReferenceCollection());
// Add this particular reference
referenceInfo.add(reference);
}
List getTopLevelStatements() {
return Collections.unmodifiableList(topLevelStatements);
}
/** Determines whether the given value is eligible to be moved across modules. */
private boolean canMoveValue(Scope scope, Node valueNode) {
// the value is only movable if it's
// - nothing,
// - a constant literal,
// - a function
// - class without computed properties, or whose computed properties expressions are moveable
// - an array/object literal of movable values
// - a template literal with movable substitutions
// - a function stub generated by CrossChunkMethodMotion.
if (valueNode == null || NodeUtil.isLiteralValue(valueNode, true) || valueNode.isFunction()) {
return true;
}
switch (valueNode.getToken()) {
case CLASS:
// NOTE: Why aren't class extends expressions checked here?
Node classMembers = valueNode.getLastChild();
for (Node member = classMembers.getFirstChild();
member != null;
member = member.getNext()) {
if (member.isComputedProp()) {
Node keyExpr = member.getFirstChild();
Node method = member.getLastChild();
checkState(method.isFunction(), method);
if (!canMoveValue(scope, keyExpr)) {
return false;
}
} else {
checkState(member.isMemberFunctionDef() || NodeUtil.isGetOrSetKey(member), member);
}
}
return true;
case CALL:
// In general it is not safe to move function calls, but we carve out an exception
// for the special stub method calls used for CrossChunkMethodMotion.
// Case: `JSCompiler_stubMethod(x)`
Node functionName = checkNotNull(valueNode.getFirstChild());
return functionName.isName()
&& functionName.getString().equals(CrossChunkMethodMotion.STUB_METHOD_NAME);
case ARRAYLIT:
// Movable if all of the array values are movable.
for (Node child = valueNode.getFirstChild(); child != null; child = child.getNext()) {
if (!canMoveValue(scope, child)) {
return false;
}
}
return true;
case OBJECTLIT:
// Movable if all of the keys and values are movable.
for (Node child = valueNode.getFirstChild(); child != null; child = child.getNext()) {
switch (child.getToken()) {
case MEMBER_FUNCTION_DEF:
case GETTER_DEF:
case SETTER_DEF:
break;
case COMPUTED_PROP:
if (!canMoveValue(scope, child.getFirstChild())
|| !canMoveValue(scope, child.getLastChild())) {
return false;
}
break;
case STRING_KEY:
case OBJECT_SPREAD:
if (!canMoveValue(scope, child.getOnlyChild())) {
return false;
}
break;
default:
throw new IllegalStateException(
"Unexpected child of OBJECTLIT: " + child.toStringTree());
}
}
return true;
case NAME:
// If the value is guaranteed to never be changed after
// this reference, then we can move it.
Var v = scope.getVar(valueNode.getString());
if (v != null && v.isGlobal()) {
ReferenceCollection refCollection = getReferences(v);
if (refCollection != null
&& refCollection.isWellDefined()
&& refCollection.isAssignedOnceInLifetime()) {
return true;
}
}
break;
case TEMPLATELIT:
// A template literal is movable if all of the substitutions it contains are movable.
for (Node child = valueNode.getFirstChild(); child != null; child = child.getNext()) {
if (child.isTemplateLitSub()) {
if (!canMoveValue(scope, child.getFirstChild())) {
return false;
}
} else {
checkState(child.isTemplateLitString(), child);
}
}
return true;
default:
break;
}
return false;
}
/** Represents a top-level statement and the references to global names it contains. */
final class TopLevelStatement {
/** 0-based index indicating original order of this statement in the source. */
private final int originalOrder;
private final JSModule module;
private final Node statementNode;
private final List nonDeclarationReferences;
private final Reference declaredNameReference;
private final Node declaredValueNode;
TopLevelStatement(TopLevelStatementDraft draft) {
this.originalOrder = draft.originalOrder;
this.module = draft.module;
this.statementNode = draft.statementNode;
this.nonDeclarationReferences = Collections.unmodifiableList(draft.nonDeclarationReferences);
this.declaredNameReference = draft.declaredNameReference;
this.declaredValueNode = draft.declaredValueNode;
}
int getOriginalOrder() {
return originalOrder;
}
JSModule getModule() {
return module;
}
Node getStatementNode() {
return statementNode;
}
List getNonDeclarationReferences() {
return Collections.unmodifiableList(nonDeclarationReferences);
}
boolean isDeclarationStatement() {
return declaredNameReference != null;
}
Reference getDeclaredNameReference() {
return checkNotNull(declaredNameReference);
}
@Nullable
Node getDeclaredValueNode() {
return declaredValueNode;
}
boolean isMovableDeclaration() {
return isDeclarationStatement()
&& canMoveValue(declaredNameReference.getScope(), declaredValueNode);
}
}
/** Holds statement info temporarily while the statement is being traversed. */
private static final class TopLevelStatementDraft {
/** 0-based index indicating original order of this statement in the source. */
final int originalOrder;
final JSModule module;
final Node statementNode;
final List nonDeclarationReferences = new ArrayList<>();
Node declaredValueNode = null;
Node declaredNameNode = null;
Reference declaredNameReference = null;
TopLevelStatementDraft(int originalOrder, JSModule module, Node statementNode) {
this.originalOrder = originalOrder;
this.module = module;
this.statementNode = statementNode;
}
}
}
