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/*
* Copyright 2009 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.base.Predicate;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.javascript.jscomp.NodeUtil.Visitor;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.function.Supplier;
/**
* A nifty set of functions to deal with the issues of replacing function parameters with a set of
* call argument expressions.
*/
class FunctionArgumentInjector {
// A string to use to represent "this". Anything that is not a valid
// identifier can be used, so we use "this".
static final String THIS_MARKER = "this";
static final String REST_MARKER = "rest param";
private final AstAnalyzer astAnalyzer;
FunctionArgumentInjector(AstAnalyzer astAnalyzer) {
this.astAnalyzer = astAnalyzer;
}
/**
* With the map provided, replace the names with expression trees.
*
* @param node The root node of the tree within which to perform the substitutions.
* @param parent The parent root node.
* @param replacements The map of names to template node trees with which to replace the name
* Nodes.
* @return The root node or its replacement.
*/
Node inject(AbstractCompiler compiler, Node node, Node parent, Map replacements) {
return inject(compiler, node, parent, replacements, /* replaceThis= */ true);
}
private Node inject(
AbstractCompiler compiler,
Node node,
Node parent,
Map replacements,
boolean replaceThis) {
if (node.isName()) {
Node replacementTemplate = replacements.get(node.getString());
if (replacementTemplate != null) {
// This should not be replacing declared names.
checkState(!(parent.isFunction() || parent.isVar() || parent.isCatch()), parent);
// The name may need to be replaced more than once,
// so we need to clone the node.
Node replacement = replacementTemplate.cloneTree();
node.replaceWith(replacement);
return replacement;
}
} else if (replaceThis && node.isThis()) {
Node replacementTemplate = replacements.get(THIS_MARKER);
checkNotNull(replacementTemplate);
if (!replacementTemplate.isThis()) {
// The name may need to be replaced more than once,
// so we need to clone the node.
Node replacement = replacementTemplate.cloneTree();
node.replaceWith(replacement);
// Remove the value. This isn't required but it ensures that we won't
// inject side-effects multiple times as it will trigger the null
// check above if we do.
if (compiler.getAstAnalyzer().mayHaveSideEffects(replacementTemplate)) {
replacements.remove(THIS_MARKER);
}
return replacement;
}
} else if (node.isFunction() && !node.isArrowFunction()) {
// Once we enter another non-arrow function the "this" value changes. Don't try
// to replace it within an inner scope.
replaceThis = false;
}
for (Node c = node.getFirstChild(); c != null; c = c.getNext()) {
// We have to reassign c in case it was replaced, because the removed c's
// getNext() would no longer be correct.
c = inject(compiler, c, node, replacements, replaceThis);
}
return node;
}
/** Get a mapping for function parameter names to call arguments. */
ImmutableMap getFunctionCallParameterMap(
final Node fnNode, Node callNode, Supplier safeNameIdSupplier) {
checkNotNull(fnNode);
// Create an parameterName -> expression map
ImmutableMap.Builder argMap = ImmutableMap.builder();
// CALL NODE: [ NAME, ARG1, ARG2, ... ]
Node cArg = callNode.getSecondChild();
if (cArg != null && NodeUtil.isFunctionObjectCall(callNode)) {
argMap.put(THIS_MARKER, cArg);
cArg = cArg.getNext();
} else {
// 'apply' isn't supported yet.
checkState(!NodeUtil.isFunctionObjectApply(callNode), callNode);
argMap.put(THIS_MARKER, NodeUtil.newUndefinedNode(callNode));
}
for (Node fnParam = NodeUtil.getFunctionParameters(fnNode).getFirstChild();
fnParam != null;
fnParam = fnParam.getNext()) {
if (cArg != null) {
if (fnParam.isRest()) {
checkState(fnParam.getOnlyChild().isName(), fnParam.getOnlyChild());
Node array = IR.arraylit();
array.srcrefTreeIfMissing(cArg);
while (cArg != null) {
array.addChildToBack(cArg.cloneTree());
cArg = cArg.getNext();
}
argMap.put(fnParam.getOnlyChild().getString(), array);
return argMap.buildOrThrow();
} else {
checkState(fnParam.isName(), fnParam);
argMap.put(fnParam.getString(), cArg);
}
cArg = cArg.getNext();
} else { // cArg != null
if (fnParam.isRest()) {
checkState(fnParam.getOnlyChild().isName(), fnParam);
// No arguments for REST parameters
Node array = IR.arraylit().srcref(fnParam);
argMap.put(fnParam.getOnlyChild().getString(), array);
} else {
checkState(fnParam.isName(), fnParam);
Node srcLocation = callNode;
argMap.put(fnParam.getString(), NodeUtil.newUndefinedNode(srcLocation));
}
}
}
// Add temp names for arguments that don't have named parameters in the
// called function.
while (cArg != null) {
String uniquePlaceholder = getUniqueAnonymousParameterName(safeNameIdSupplier);
argMap.put(uniquePlaceholder, cArg);
cArg = cArg.getNext();
}
return argMap.buildOrThrow();
}
/** Parameter names will be name unique when at a later time. */
private static String getUniqueAnonymousParameterName(Supplier safeNameIdSupplier) {
return "JSCompiler_inline_anon_param_" + safeNameIdSupplier.get();
}
/**
* Retrieve a set of names that can not be safely substituted in place.
*
* Example:
*
* function(a) {
* a = 0;
* }
*
Inlining this without taking precautions would cause the call site value to be modified
* (bad).
*/
Set findModifiedParameters(Node fnNode) {
ImmutableSet names = getFunctionParameterSet(fnNode);
Set unsafeNames = new LinkedHashSet<>();
return findModifiedParameters(fnNode.getLastChild(), names, unsafeNames, false);
}
/**
* Check for uses of the named value that imply a pass-by-value parameter is expected. This is
* used to prevent cases like:
*
* function (x) { x=2; return x; }
*
*
We don't want "undefined" to be substituted for "x", and get undefined=2
*
* @param n The node in question.
* @param names The set of names to check.
* @param unsafe The set of names that require aliases.
* @param inInnerFunction Whether the inspection is occurring on a inner function.
*/
private static Set findModifiedParameters(
Node n, ImmutableSet names, Set unsafe, boolean inInnerFunction) {
checkArgument(unsafe != null);
if (n.isName()) {
if (names.contains(n.getString()) && (inInnerFunction || canNameValueChange(n))) {
unsafe.add(n.getString());
}
} else if (n.isFunction()) {
// A function parameter can not be replaced with a direct inlined value
// if it is referred to by an inner function. The inner function
// can out live the call we are replacing, so inner function must
// capture a unique name. This approach does not work within loop
// bodies so those are forbidden elsewhere.
inInnerFunction = true;
}
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
findModifiedParameters(c, names, unsafe, inInnerFunction);
}
return unsafe;
}
/**
* This is similar to NodeUtil.isLValue except that object properties and array member
* modification aren't important ("o" in "o.a = 2" is still "o" after assignment, where in as "o =
* x", "o" is now "x").
*
* This also looks for the redefinition of a name. function (x) {var x;}
*
* @param n The NAME node in question.
*/
private static boolean canNameValueChange(Node n) {
return NodeUtil.isLValue(n)
&& !NodeUtil.getEnclosingStatement(n).isConst()
&& !NodeUtil.getEnclosingStatement(n).isLet();
}
/**
* Updates the set of parameter names that correspond to arguments from the call site that require
* aliases.
*
*
If an argument requires a temp (e.g. it is side-effectful, affects mutable state or due to
* other reasons), we need to evaluate it into a temporary at the callsite before inlining the
* function block into that callsite. However, that argument's early evaluation could also change
* the values of previous arguments. Hence, in this function we decide to hoist all those previous
* args and evaluate them before this side-effectful argument, even if they are not actually
* affected by that side-effectful argument. This simplifies the implementation and doesn't hurt
* performance.
*
*
This method populates the given namesNeedingTemps set with all the parameter names that
* require hoisting with a temp.
*
* @param fnNode The FUNCTION node to be inlined.
* @param argMap The argument list for the call to fnNode.
* @param namesNeedingTemps The set of names to update.
*/
void maybeAddTempsForCallArguments(
AbstractCompiler compiler,
Node fnNode,
ImmutableMap argMap,
Set namesNeedingTemps,
CodingConvention convention) {
if (argMap.isEmpty()) {
// No arguments to check, we are done.
return;
}
checkArgument(fnNode.isFunction(), fnNode);
Node block = fnNode.getLastChild();
/*
* This field holds the parameter name corresponding to the last side-effectful argument. Args
* corresponding to all parameters before and including this parameter name would get hoisted
* using temps.
*/
String requiresTempsUpToThisParameterName = "";
int argCount = argMap.size();
// We limit the "trivial" bodies to those where there is a single expression or
// return, the expression is
boolean isTrivialBody =
(!block.hasChildren()
|| (block.hasOneChild() && !bodyMayHaveConditionalCode(block.getLastChild())));
boolean hasMinimalParameters =
NodeUtil.isUndefined(argMap.get(THIS_MARKER)) && argCount <= 2; // this + one parameter
// Get the list of parameters that may need temporaries due to side-effects.
ImmutableSet namesAfterSideEffects =
findParametersReferencedAfterSideEffect(argMap.keySet(), block);
// Check for arguments that are evaluated more than once.
for (Map.Entry entry : argMap.entrySet()) {
String parameterName = entry.getKey();
Node cArg = entry.getValue();
if (namesNeedingTemps.contains(parameterName)) {
requiresTempsUpToThisParameterName = parameterName;
continue;
}
// Stores whether this arg need to get hoisted using a temporary
boolean requiresTemporary = false;
final int references = NodeUtil.getNameReferenceCount(block, parameterName);
boolean argSideEffects = compiler.getAstAnalyzer().mayHaveSideEffects(cArg);
if (!argSideEffects && references == 0) {
requiresTemporary = false;
} else if (isTrivialBody
&& hasMinimalParameters
&& references == 1
&& !(NodeUtil.canBeSideEffected(cArg) && namesAfterSideEffects.contains(parameterName))) {
// For functions with a trivial body, and where the parameter evaluation order
// can't change, and there aren't any side-effect before the parameter, we can
// avoid creating a temporary.
//
// This is done to help inline common trivial functions
requiresTemporary = false;
} else if (compiler.getAstAnalyzer().mayEffectMutableState(cArg) && references > 0) {
// Note: Mutable arguments should be assigned to temps, as the
// may be within in a loop:
// function x(a) {
// for(var i=0; i<0; i++) {
// foo(a);
// }
// x( [] );
// The parameter in the call to foo should not become "[]".
requiresTemporary = true;
} else if (argSideEffects) {
// even if there are no references, we still need to evaluate the
// expression if it has side-effects.
requiresTemporary = true;
} else if (NodeUtil.canBeSideEffected(cArg)
&& namesAfterSideEffects.contains(parameterName)) {
requiresTemporary = true;
} else if (references > 1) {
// Safe is a misnomer, this is a check for "large".
switch (cArg.getToken()) {
case NAME:
String name = cArg.getString();
// Don't worry about whether this is global or local, just check if it is
// "exported" in either case.
requiresTemporary =
(convention.isExported(name, true) || convention.isExported(name, false));
break;
case THIS:
requiresTemporary = false;
break;
case STRINGLIT:
requiresTemporary = (cArg.getString().length() >= 2);
break;
default:
requiresTemporary = !NodeUtil.isImmutableValue(cArg);
break;
}
}
if (requiresTemporary) {
requiresTempsUpToThisParameterName = parameterName;
}
}
if (!requiresTempsUpToThisParameterName.isEmpty()) {
// mark all names upto requiresTempsUptoParameterName as namesNeedingTemps
for (Map.Entry entry : argMap.entrySet()) {
String parameterName = entry.getKey();
if (parameterName.equals(THIS_MARKER) && NodeUtil.isUndefined(argMap.get(THIS_MARKER))) {
/* When there is no explicit this arg passed into the call, the argMap contains an entry
* <"this", undefined Node>. See the `getFunctionCallParameterMap` method.
*
* We do not want to add an unnecessary temp for "this", when there wasn't an explicit
* "this" passed in at the callsite. That is, we want to transform a call-site like:
* {@code `foo(a,b)`}
* to
* {@code `let a$inline$0 = a; foo(a$inline$0 ,b)`}
* and not
* {@code `let this$inline$0 = this; let a$inline$0=a; foo(a$inline$0, b)`}.
* Hence we skip generating a temporary for an implicit "this" arg
*/
continue;
}
// TODO: b/298828688 Use `NodeUtil.isImmutableValue` to detect some simple immutable cases
// and skip generating temps for those as well.
if (parameterName.equals(requiresTempsUpToThisParameterName)) {
namesNeedingTemps.add(parameterName);
break;
} else {
namesNeedingTemps.add(parameterName);
}
}
}
}
/**
* We consider a return or expression trivial if it doesn't contain a conditional expression or a
* function.
*/
boolean bodyMayHaveConditionalCode(Node n) {
if (!n.isReturn() && !n.isExprResult()) {
return true;
}
return mayHaveConditionalCode(n);
}
/**
* We consider an expression trivial if it doesn't contain a conditional expression or a function.
*/
boolean mayHaveConditionalCode(Node n) {
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
switch (c.getToken()) {
case FUNCTION:
case AND:
case OR:
case HOOK:
case COALESCE:
case OPTCHAIN_CALL:
case OPTCHAIN_GETELEM:
case OPTCHAIN_GETPROP:
return true;
default:
break;
}
if (mayHaveConditionalCode(c)) {
return true;
}
}
return false;
}
/**
* Bootstrap a traversal to look for parameters referenced after a non-local side-effect.
*
* NOTE: This assumes no-inner functions.
*
* @param parameters The set of parameter names.
* @param root The function code block.
* @return The subset of parameters referenced after the first seen non-local side-effect.
*/
private ImmutableSet findParametersReferencedAfterSideEffect(
ImmutableSet parameters, Node root) {
// TODO(johnlenz): Consider using scope for this.
Set locals = new LinkedHashSet<>(parameters);
gatherLocalNames(root, locals);
ReferencedAfterSideEffect collector =
new ReferencedAfterSideEffect(parameters, ImmutableSet.copyOf(locals));
NodeUtil.visitPostOrder(root, collector, collector);
return collector.getResults();
}
/**
* Collect parameter names referenced after a non-local side-effect.
*
* Assumptions:
*
*
* - We assume parameters are not modified in the function body (that is checked separately).
*
- There are no inner functions (also checked separately).
*
*
* As we are trying to replace parameters with there passed in values we are interested in
* anything that may affect those value. So, ignoring changes to local variables, we look for
* things that may affect anything outside the local-state. Once such a side-effect is seen any
* following reference to the function parameters are collected. These will need to be assigned to
* temporaries to prevent changes to their value as would have happened during the function call.
*
*
To properly handle loop structures all references to the function parameters are recorded
* and the decision to keep or throw away those references is deferred until exiting the loop
* structure.
*/
private class ReferencedAfterSideEffect implements Visitor, Predicate {
private final ImmutableSet parameters;
private final ImmutableSet locals;
private boolean sideEffectSeen = false;
private final Set parametersReferenced = new LinkedHashSet<>();
private int loopsEntered = 0;
ReferencedAfterSideEffect(ImmutableSet parameters, ImmutableSet locals) {
this.parameters = parameters;
this.locals = locals;
}
ImmutableSet getResults() {
return ImmutableSet.copyOf(parametersReferenced);
}
@Override
public boolean apply(Node node) {
// Keep track of any loop structures entered.
if (NodeUtil.isLoopStructure(node)) {
loopsEntered++;
}
// If we have found all the parameters, don't bother looking
// at the children.
return !(sideEffectSeen && parameters.size() == parametersReferenced.size());
}
boolean inLoop() {
return loopsEntered != 0;
}
@Override
public void visit(Node n) {
// If we are exiting a loop.
if (NodeUtil.isLoopStructure(n)) {
loopsEntered--;
if (!inLoop() && !sideEffectSeen) {
// Now that the loops has been fully traversed and
// no side-effects have been seen, throw away
// the references seen in them.
parametersReferenced.clear();
}
}
if (!sideEffectSeen) {
// Look for side-effects.
if (hasNonLocalSideEffect(n)) {
sideEffectSeen = true;
}
}
// If traversing the nodes of a loop save any references
// that are seen.
if (inLoop() || sideEffectSeen) {
// Record references to parameters.
if (n.isName()) {
String name = n.getString();
if (parameters.contains(name)) {
parametersReferenced.add(name);
}
} else if (n.isThis()) {
parametersReferenced.add(THIS_MARKER);
}
}
}
/**
* @return Whether the node may have non-local side-effects.
*/
private boolean hasNonLocalSideEffect(Node n) {
boolean sideEffect = false;
Token type = n.getToken();
// Note: Only care about changes to non-local names, specifically
// ignore VAR declaration assignments.
if (NodeUtil.isAssignmentOp(n) || type == Token.INC || type == Token.DEC) {
Node lhs = n.getFirstChild();
// Ignore changes to local names.
if (!isLocalName(lhs)) {
sideEffect = true;
}
} else if (type == Token.CALL) {
sideEffect = astAnalyzer.functionCallHasSideEffects(n);
} else if (type == Token.NEW) {
sideEffect = astAnalyzer.constructorCallHasSideEffects(n);
} else if (type == Token.DELPROP) {
sideEffect = true;
}
return sideEffect;
}
/**
* @return Whether node is a reference to locally declared name.
*/
private boolean isLocalName(Node node) {
if (node.isName()) {
String name = node.getString();
return locals.contains(name);
}
return false;
}
}
/** Gather any names declared in the local scope. */
private static void gatherLocalNames(Node n, Set names) {
if (n.isFunction()) {
if (NodeUtil.isFunctionDeclaration(n)) {
names.add(n.getFirstChild().getString());
}
// Don't traverse into inner function scopes;
return;
} else if (n.isName()) {
switch (n.getParent().getToken()) {
case VAR:
case LET:
case CONST:
case CATCH:
names.add(n.getString());
break;
default:
break;
}
}
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
gatherLocalNames(c, names);
}
}
/** Get a set of function parameter names. */
private static ImmutableSet getFunctionParameterSet(Node fnNode) {
ImmutableSet.Builder builder = ImmutableSet.builder();
for (Node n = NodeUtil.getFunctionParameters(fnNode).getFirstChild();
n != null;
n = n.getNext()) {
if (n.isRest()) {
builder.add(REST_MARKER);
} else if (n.isDefaultValue() || n.isObjectPattern() || n.isArrayPattern()) {
throw new IllegalStateException("Not supported: " + n);
} else {
builder.add(n.getString());
}
}
return builder.build();
}
}