com.google.javascript.jscomp.PureFunctionIdentifier Maven / Gradle / Ivy
/*
* 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.MoreObjects;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Multimap;
import com.google.common.collect.SetMultimap;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.Immutable;
import com.google.javascript.jscomp.CodingConvention.Cache;
import com.google.javascript.jscomp.DefinitionsRemover.Definition;
import com.google.javascript.jscomp.NodeTraversal.ScopedCallback;
import com.google.javascript.jscomp.graph.DiGraph;
import com.google.javascript.jscomp.graph.DiGraph.DiGraphNode;
import com.google.javascript.jscomp.graph.FixedPointGraphTraversal;
import com.google.javascript.jscomp.graph.LinkedDirectedGraph;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import com.google.javascript.rhino.jstype.FunctionType;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.JSTypeNative;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Predicate;
import javax.annotation.Nullable;
/**
* Compiler pass that computes function purity and annotates invocation nodes with those purities.
*
* A function is pure if it has no outside visible side effects, and the result of the
* computation does not depend on external factors that are beyond the control of the application;
* repeated calls to the function should return the same value as long as global state hasn't
* changed.
*
*
`Date.now` is an example of a function that has no side effects but is not pure.
*
*
Functions are not tracked individually but rather in aggregate by their name. This is because
* it's impossible to determine exactly which function named "foo" is being called at a particular
* site. Therefore, if any function "foo" has a particular side-effect, all
* invocations "foo" are assumed to trigger it.
*
*
This pass could be greatly improved by proper tracking of locals within function bodies. Every
* instance of the call to {@link NodeUtil#evaluatesToLocalValue(Node)} and {@link
* NodeUtil#allArgsUnescapedLocal(Node)} do not actually take into account local variables. They
* only assume literals, primitives, and operations on primitives are local.
*
* @author [email protected] (John Lenz)
* @author [email protected] (Thomas Deegan)
*/
class PureFunctionIdentifier implements CompilerPass {
private final AbstractCompiler compiler;
private final NameBasedDefinitionProvider definitionProvider;
/**
* Map of function names to the summary of the functions with that name.
*
* @see {@link AmbiguatedFunctionSummary}
*/
private final Map summaryByName = new HashMap<>();
/**
* Mapping from function node to side effects for all names associated with that node.
*
* This is a multimap because you can construct situations in which a function node has
* multiple names, and therefore multiple associated side-effect infos. For example:
*
*
* // Not enough type information to collapse/disambiguate properties on "staticMethod".
* SomeClass.staticMethod = function anotherName() {};
* OtherClass.staticMethod = function() { global++; }
*
*
* In this situation we want to keep the side effects for "staticMethod" which are "global"
* separate from "anotherName". Hence the function node should point to the {@link
* AmbiguatedFunctionSummary} for both "staticMethod" and "anotherName".
*
*
We could instead store a map of FUNCTION nodes to names, and then join that with the name of
* names to infos. However, since names are 1:1 with infos, it's more effecient to "pre-join" in
* this way.
*/
private final Multimap summariesForAllNamesOfFunctionByNode;
// List of all function call sites; used to iterate in markPureFunctionCalls.
private final List allFunctionCalls;
/**
* A graph linking the summary of function callees to the summaries of their callers.
*
* The edge values indicate the details of the invocation necessary to propagate function
* purity from callee to caller.
*/
private final LinkedDirectedGraph
reverseCallGraph = LinkedDirectedGraph.createWithoutAnnotations();
// Externs and ast tree root, for use in getDebugReport. These two
// fields are null until process is called.
private Node externs;
private Node root;
public PureFunctionIdentifier(
AbstractCompiler compiler, NameBasedDefinitionProvider definitionProvider) {
this.compiler = checkNotNull(compiler);
this.definitionProvider = definitionProvider;
this.summariesForAllNamesOfFunctionByNode = ArrayListMultimap.create();
this.allFunctionCalls = new ArrayList<>();
this.externs = null;
this.root = null;
}
@Override
public void process(Node externsAst, Node srcAst) {
checkState(
externs == null && root == null,
"PureFunctionIdentifier::process may only be called once per instance.");
externs = externsAst;
root = srcAst;
buildReverseCallGraph();
NodeTraversal.traverse(compiler, externs, new FunctionAnalyzer(true));
NodeTraversal.traverse(compiler, root, new FunctionAnalyzer(false));
propagateSideEffects();
markPureFunctionCalls();
}
/**
* Unwraps a complicated expression to reveal directly callable nodes that correspond to
* definitions. For example: (a.c || b) or (x ? a.c : b) are turned into [a.c, b]. Since when you
* call
*
*
* var result = (a.c || b)(some, parameters);
*
*
* either a.c or b are called.
*
* @param exp A possibly complicated expression.
* @return A list of GET_PROP NAME and function expression nodes (all of which can be called). Or
* null if any of the callable nodes are of an unsupported type. e.g. x['asdf'](param);
*/
@Nullable
private static Iterable unwrapCallableExpression(Node exp) {
switch (exp.getToken()) {
case GETPROP:
if (isCallOrApply(exp.getParent())) {
return unwrapCallableExpression(exp.getFirstChild());
}
return ImmutableList.of(exp);
case FUNCTION:
case NAME:
return ImmutableList.of(exp);
case OR:
case HOOK:
Node firstVal;
if (exp.isHook()) {
firstVal = exp.getSecondChild();
} else {
firstVal = exp.getFirstChild();
}
Iterable firstCallable = unwrapCallableExpression(firstVal);
Iterable secondCallable = unwrapCallableExpression(firstVal.getNext());
if (firstCallable == null || secondCallable == null) {
return null;
}
return Iterables.concat(firstCallable, secondCallable);
default:
return null; // Unsupported call type.
}
}
private static boolean isSupportedFunctionDefinition(@Nullable Node definitionRValue) {
if (definitionRValue == null) {
return false;
}
switch (definitionRValue.getToken()) {
case FUNCTION:
return true;
case HOOK:
return isSupportedFunctionDefinition(definitionRValue.getSecondChild())
&& isSupportedFunctionDefinition(definitionRValue.getLastChild());
default:
return false;
}
}
private Iterable getGoogCacheCallableExpression(Cache cacheCall) {
checkNotNull(cacheCall);
if (cacheCall.keyFn == null) {
return unwrapCallableExpression(cacheCall.valueFn);
}
return Iterables.concat(
unwrapCallableExpression(cacheCall.valueFn), unwrapCallableExpression(cacheCall.keyFn));
}
@Nullable
private List getSummariesForCallee(Node invocation) {
checkArgument(NodeUtil.isInvocation(invocation), invocation);
Iterable expanded;
Cache cacheCall = compiler.getCodingConvention().describeCachingCall(invocation);
if (cacheCall != null) {
expanded = getGoogCacheCallableExpression(cacheCall);
} else {
expanded = unwrapCallableExpression(invocation.getFirstChild());
}
if (expanded == null) {
return null;
}
List results = new ArrayList<>();
for (Node expression : expanded) {
if (NodeUtil.isFunctionExpression(expression)) {
// isExtern is false in the call to the constructor for the
// FunctionExpressionDefinition below because we know that
// getFunctionDefinitions() will only be called on the first
// child of an invocation and thus the function expression
// definition will never be an extern.
results.addAll(summariesForAllNamesOfFunctionByNode.get(expression));
continue;
}
String name = DefinitionsRemover.Definition.getSimplifiedName(expression);
AmbiguatedFunctionSummary info = null;
if (name != null) {
info = summaryByName.get(name);
}
if (info != null) {
results.add(info);
} else {
return null;
}
}
return results;
}
/**
* Construct an "ambiguated" reverse call graph where all functions of the same name are unified
* to a single node, and edges point from callee to caller.
*
* When propagating side effects we construct a graph from every function definition A to every
* function definition B that calls A(). Since the definition provider cannot always provide a
* unique definition for a name, there may be many possible definitions for a given call site. In
* the case where multiple defs share the same node in the graph.
*
*
We need to build the map {@link PureFunctionIdentifier#summaryByName} to get a reference to
* the side effects for a call and we need the map {@link #summariesForAllNamesOfFunctionByNode}
* to get a reference to the side effects for a given function node.
*/
private void buildReverseCallGraph() {
final AmbiguatedFunctionSummary unknownDefinitionFunction =
AmbiguatedFunctionSummary.createInGraph(reverseCallGraph, "");
unknownDefinitionFunction.setMutatesGlobalState();
unknownDefinitionFunction.setFunctionThrows();
unknownDefinitionFunction.setEscapedReturn();
for (DefinitionSite site : definitionProvider.getDefinitionSites()) {
Definition definition = site.definition;
if (definition.getLValue() != null) {
Node getOrName = definition.getLValue();
checkArgument(getOrName.isGetProp() || getOrName.isName(), getOrName);
String name = DefinitionsRemover.Definition.getSimplifiedName(getOrName);
checkNotNull(name);
if (isSupportedFunctionDefinition(definition.getRValue())) {
addSupportedDefinition(site, name);
} else {
// Unsupported function definition. Mark a global side effect here since we don't
// actually know anything about what's being defined.
AmbiguatedFunctionSummary info = summaryByName.get(name);
if (info != null) {
info.setMutatesGlobalState();
info.setFunctionThrows();
info.setEscapedReturn();
} else {
summaryByName.put(name, unknownDefinitionFunction);
}
}
}
}
}
/**
* Add the definition to the {@link #reverseCallGraph} as a {@link AmbiguatedFunctionSummary} node
* or link it to the existing {@link AmbiguatedFunctionSummary} node if there is already a
* function with the same definition name.
*/
private void addSupportedDefinition(DefinitionSite definitionSite, String name) {
for (Node function : unwrapCallableExpression(definitionSite.definition.getRValue())) {
// A function may have multiple definitions.
// Link this function definition to the existing summary node.
AmbiguatedFunctionSummary summary = summaryByName.get(name);
if (summary == null) {
// Need to create a function info node.
summary = AmbiguatedFunctionSummary.createInGraph(reverseCallGraph, name);
// Keep track of this so that later functions of the same name can point to the same
// AmbiguatedFunctionSummary.
summaryByName.put(name, summary);
}
summariesForAllNamesOfFunctionByNode.put(function, summary);
if (definitionSite.inExterns) {
// Externs have their side effects computed here, otherwise in FunctionAnalyzer.
summary.updateSideEffectsFromExtern(function, compiler);
}
}
}
/**
* Propagate side effect information in {@link #reverseCallGraph} from callees to callers.
*
* This is an iterative process executed until a fixed point, where no caller summary would be
* given new side-effects from from any callee summary, is reached.
*/
private void propagateSideEffects() {
FixedPointGraphTraversal.newTraversal(
(AmbiguatedFunctionSummary source,
CallSitePropagationInfo edge,
AmbiguatedFunctionSummary destination) -> edge.propagate(source, destination))
.computeFixedPoint(reverseCallGraph);
}
/** Set no side effect property at pure-function call sites. */
private void markPureFunctionCalls() {
for (Node callNode : allFunctionCalls) {
List calleeSummaries = getSummariesForCallee(callNode);
// Default to side effects, non-local results
Node.SideEffectFlags flags = new Node.SideEffectFlags();
if (calleeSummaries == null) {
flags.setMutatesGlobalState();
flags.setThrows();
flags.setReturnsTainted();
} else {
flags.clearAllFlags();
for (AmbiguatedFunctionSummary calleeSummary : calleeSummaries) {
checkNotNull(calleeSummary);
if (calleeSummary.mutatesGlobalState()) {
flags.setMutatesGlobalState();
}
if (calleeSummary.mutatesArguments()) {
flags.setMutatesArguments();
}
if (calleeSummary.functionThrows()) {
flags.setThrows();
}
if (isCallOrTaggedTemplateLit(callNode)) {
if (calleeSummary.mutatesThis()) {
// A FunctionInfo for "f" maps to both "f()" and "f.call()" nodes.
if (isCallOrApply(callNode)) {
flags.setMutatesArguments(); // `this` is actually an argument.
} else {
flags.setMutatesThis();
}
}
}
if (calleeSummary.escapedReturn()) {
flags.setReturnsTainted();
}
}
}
// Handle special cases (Math, RegExp)
if (isCallOrTaggedTemplateLit(callNode)) {
if (!NodeUtil.functionCallHasSideEffects(callNode, compiler)) {
flags.clearSideEffectFlags();
}
} else if (callNode.isNew()) {
// Handle known cases now (Object, Date, RegExp, etc)
if (!NodeUtil.constructorCallHasSideEffects(callNode)) {
flags.clearSideEffectFlags();
}
}
int newSideEffectFlags = flags.valueOf();
if (callNode.getSideEffectFlags() != newSideEffectFlags) {
callNode.setSideEffectFlags(newSideEffectFlags);
compiler.reportChangeToEnclosingScope(callNode);
}
}
}
private static final Predicate RHS_IS_ALWAYS_LOCAL = lhs -> true;
private static final Predicate RHS_IS_NEVER_LOCAL = lhs -> false;
private static final Predicate FIND_RHS_AND_CHECK_FOR_LOCAL_VALUE = lhs -> {
Node rhs = NodeUtil.getRValueOfLValue(lhs);
return rhs == null || NodeUtil.evaluatesToLocalValue(rhs);
};
/**
* Gather list of functions, functions with @nosideeffects annotations, call sites, and functions
* that may mutate variables not defined in the local scope.
*/
private class FunctionAnalyzer implements ScopedCallback {
private final SetMultimap blacklistedVarsByFunction = HashMultimap.create();
private final SetMultimap taintedVarsByFunction = HashMultimap.create();
private final boolean inExterns;
FunctionAnalyzer(boolean inExterns) {
this.inExterns = inExterns;
}
@Override
public boolean shouldTraverse(NodeTraversal traversal, Node node, Node parent) {
// Functions need to be processed as part of pre-traversal so that an entry for the function
// exists in the summariesForAllNamesOfFunctionByNode map when processing assignments and
// calls within the body.
if (node.isFunction() && !summariesForAllNamesOfFunctionByNode.containsKey(node)) {
// This function was not part of a definition which is why it was not created by
// {@link buildReverseCallGraph}. For example, an anonymous function.
AmbiguatedFunctionSummary summary =
AmbiguatedFunctionSummary.createInGraph(reverseCallGraph, "");
summariesForAllNamesOfFunctionByNode.put(node, summary);
}
return true;
}
@Override
public void visit(NodeTraversal traversal, Node node, Node parent) {
if (inExterns) {
return;
}
if (!NodeUtil.nodeTypeMayHaveSideEffects(node, compiler) && !node.isReturn()) {
return;
}
if (NodeUtil.isInvocation(node)) {
allFunctionCalls.add(node);
}
Scope containerScope = traversal.getScope().getClosestContainerScope();
if (!containerScope.isFunctionScope()) {
// We only need to look at nodes in function scopes.
return;
}
Node enclosingFunction = containerScope.getRootNode();
for (AmbiguatedFunctionSummary encloserSummary :
summariesForAllNamesOfFunctionByNode.get(enclosingFunction)) {
checkNotNull(encloserSummary);
updateSideEffectsForNode(encloserSummary, traversal, node, enclosingFunction);
}
}
public void updateSideEffectsForNode(
AmbiguatedFunctionSummary encloserSummary,
NodeTraversal traversal,
Node node,
Node enclosingFunction) {
switch (node.getToken()) {
case ASSIGN:
// e.g.
// lhs = rhs;
// ({x, y} = object);
visitLhsNodes(
encloserSummary,
traversal.getScope(),
enclosingFunction,
NodeUtil.findLhsNodesInNode(node),
FIND_RHS_AND_CHECK_FOR_LOCAL_VALUE);
break;
case INC: // e.g. x++;
case DEC:
case DELPROP:
visitLhsNodes(
encloserSummary,
traversal.getScope(),
enclosingFunction,
ImmutableList.of(node.getOnlyChild()),
// The value assigned by a unary op is always local.
RHS_IS_ALWAYS_LOCAL);
break;
case FOR_AWAIT_OF:
setSideEffectsForControlLoss(encloserSummary); // Control is lost while awaiting.
// Fall through.
case FOR_OF:
// e.g.
// for (const {prop1, prop2} of iterable) {...}
// for ({prop1: x.p1, prop2: x.p2} of iterable) {...}
//
// TODO(bradfordcsmith): Possibly we should try to determine whether the iteration itself
// could have side effects.
visitLhsNodes(
encloserSummary,
traversal.getScope(),
enclosingFunction,
NodeUtil.findLhsNodesInNode(node),
// The RHS of a for-of must always be an iterable, making it a container, so we can't
// consider its contents to be local
RHS_IS_NEVER_LOCAL);
checkIteratesImpureIterable(node, encloserSummary);
break;
case FOR_IN:
// e.g.
// for (prop in obj) {...}
// Also this, though not very useful or readable.
// for ([char1, char2, ...x.rest] in obj) {...}
visitLhsNodes(
encloserSummary,
traversal.getScope(),
enclosingFunction,
NodeUtil.findLhsNodesInNode(node),
// A for-in always assigns a string, which is a local value by definition.
RHS_IS_ALWAYS_LOCAL);
break;
case CALL:
case NEW:
case TAGGED_TEMPLATELIT:
visitCall(encloserSummary, node);
break;
case NAME:
// Variable definition are not side effects. Check that the name appears in the context of
// a variable declaration.
checkArgument(NodeUtil.isNameDeclaration(node.getParent()), node.getParent());
Node value = node.getFirstChild();
// Assignment to local, if the value isn't a safe local value,
// new object creation or literal or known primitive result
// value, add it to the local blacklist.
if (value != null && !NodeUtil.evaluatesToLocalValue(value)) {
Scope scope = traversal.getScope();
Var var = scope.getVar(node.getString());
blacklistedVarsByFunction.put(enclosingFunction, var);
}
break;
case THROW:
encloserSummary.setFunctionThrows();
break;
case RETURN:
if (node.hasChildren() && !NodeUtil.evaluatesToLocalValue(node.getFirstChild())) {
encloserSummary.setEscapedReturn();
}
break;
case YIELD:
checkIteratesImpureIterable(node, encloserSummary); // `yield*` triggers iteration.
// 'yield' throws if the caller calls `.throw` on the generator object.
setSideEffectsForControlLoss(encloserSummary);
break;
case AWAIT:
// 'await' throws if the promise it's waiting on is rejected.
setSideEffectsForControlLoss(encloserSummary);
break;
case REST:
case SPREAD:
checkIteratesImpureIterable(node, encloserSummary);
break;
default:
if (NodeUtil.isCompoundAssignmentOp(node)) {
// e.g.
// x += 3;
visitLhsNodes(
encloserSummary,
traversal.getScope(),
enclosingFunction,
ImmutableList.of(node.getFirstChild()),
// The update assignments (e.g. `+=) always assign primitive, and therefore local,
// values.
RHS_IS_ALWAYS_LOCAL);
break;
}
throw new IllegalArgumentException("Unhandled side effect node type " + node);
}
}
/**
* Inspect {@code node} for impure iteration and assign the appropriate side-effects to {@code
* encloserSummary} if so.
*/
private void checkIteratesImpureIterable(Node node, AmbiguatedFunctionSummary encloserSummary) {
if (!NodeUtil.iteratesImpureIterable(node)) {
return;
}
// Treat the (possibly implicit) call to `iterator.next()` as having the same effects as any
// other unknown function call.
encloserSummary.setFunctionThrows();
encloserSummary.setMutatesGlobalState();
// The iterable may be stateful and a param.
encloserSummary.setMutatesArguments();
}
/**
* Assigns the set of side-effects associated with an arbitrary loss of control flow to {@code
* encloserSummary}.
*/
private void setSideEffectsForControlLoss(AmbiguatedFunctionSummary encloserSummary) {
encloserSummary.setFunctionThrows();
}
@Override
public void enterScope(NodeTraversal t) {
// Nothing to do.
}
@Override
public void exitScope(NodeTraversal t) {
Scope closestContainerScope = t.getScope().getClosestContainerScope();
if (!closestContainerScope.isFunctionScope()) {
// Only functions and the scopes within them are of interest to us.
return;
}
Node function = closestContainerScope.getRootNode();
// Handle deferred local variable modifications:
for (AmbiguatedFunctionSummary sideEffectInfo :
summariesForAllNamesOfFunctionByNode.get(function)) {
checkNotNull(sideEffectInfo, "%s has no side effect info.", function);
if (sideEffectInfo.mutatesGlobalState()) {
continue;
}
for (Var v : t.getScope().getVarIterable()) {
if (v.isParam()
&& !blacklistedVarsByFunction.containsEntry(function, v)
&& taintedVarsByFunction.containsEntry(function, v)) {
sideEffectInfo.setMutatesArguments();
continue;
}
boolean localVar = false;
// Parameters and catch values can come from other scopes.
if (!v.isParam() && !v.isCatch()) {
// TODO(johnlenz): create a useful parameter list
// sideEffectInfo.addKnownLocal(v.getName());
localVar = true;
}
// Take care of locals that might have been tainted.
if (!localVar || blacklistedVarsByFunction.containsEntry(function, v)) {
if (taintedVarsByFunction.containsEntry(function, v)) {
// If the function has global side-effects
// don't bother with the local side-effects.
sideEffectInfo.setMutatesGlobalState();
break;
}
}
}
}
// Clean up memory after exiting out of the function scope where we will no longer need these.
if (t.getScopeRoot().isFunction()) {
blacklistedVarsByFunction.removeAll(function);
taintedVarsByFunction.removeAll(function);
}
}
private boolean isVarDeclaredInSameContainerScope(@Nullable Var v, Scope scope) {
return v != null && v.scope.hasSameContainerScope(scope);
}
/**
* Record information about the side effects caused by assigning a value to a given LHS.
*
* If the operation modifies this or taints global state, mark the enclosing function as
* having those side effects.
*
* @param sideEffectInfo Function side effect record to be updated
* @param scope variable scope in which the variable assignment occurs
* @param enclosingFunction FUNCTION node for the enclosing function
* @param lhsNodes LHS nodes that are all assigned values by a given parent node
* @param hasLocalRhs Predicate indicating whether a given LHS is being assigned a local value
*/
private void visitLhsNodes(
AmbiguatedFunctionSummary sideEffectInfo,
Scope scope,
Node enclosingFunction,
Iterable lhsNodes,
Predicate hasLocalRhs) {
for (Node lhs : lhsNodes) {
if (NodeUtil.isGet(lhs)) {
if (lhs.getFirstChild().isThis()) {
sideEffectInfo.setMutatesThis();
} else {
Node objectNode = lhs.getFirstChild();
if (objectNode.isName()) {
Var var = scope.getVar(objectNode.getString());
if (isVarDeclaredInSameContainerScope(var, scope)) {
// Maybe a local object modification. We won't know for sure until
// we exit the scope and can validate the value of the local.
taintedVarsByFunction.put(enclosingFunction, var);
} else {
sideEffectInfo.setMutatesGlobalState();
}
} else {
// Don't track multi level locals: local.prop.prop2++;
sideEffectInfo.setMutatesGlobalState();
}
}
} else {
checkState(lhs.isName(), lhs);
Var var = scope.getVar(lhs.getString());
if (isVarDeclaredInSameContainerScope(var, scope)) {
if (!hasLocalRhs.test(lhs)) {
// Assigned value is not guaranteed to be a local value,
// so if we see any property assignments on this variable,
// they could be tainting a non-local value.
blacklistedVarsByFunction.put(enclosingFunction, var);
}
} else {
sideEffectInfo.setMutatesGlobalState();
}
}
}
}
/** Record information about a call site. */
private void visitCall(AmbiguatedFunctionSummary callerInfo, Node invocation) {
// Handle special cases (Math, RegExp)
// TODO: This logic can probably be replaced with @nosideeffects annotations in externs.
if (invocation.isCall() && !NodeUtil.functionCallHasSideEffects(invocation, compiler)) {
return;
}
// Handle known cases now (Object, Date, RegExp, etc)
if (invocation.isNew() && !NodeUtil.constructorCallHasSideEffects(invocation)) {
return;
}
List calleeSummaries = getSummariesForCallee(invocation);
if (calleeSummaries == null) {
callerInfo.setMutatesGlobalState();
callerInfo.setFunctionThrows();
return;
}
for (AmbiguatedFunctionSummary calleeInfo : calleeSummaries) {
CallSitePropagationInfo edge = CallSitePropagationInfo.computePropagationType(invocation);
reverseCallGraph.connect(calleeInfo.graphNode, edge, callerInfo.graphNode);
}
}
}
private static boolean isCallOrApply(Node callSite) {
return NodeUtil.isFunctionObjectCall(callSite) || NodeUtil.isFunctionObjectApply(callSite);
}
private static boolean isCallOrTaggedTemplateLit(Node invocation) {
return invocation.isCall() || invocation.isTaggedTemplateLit();
}
/**
* This class stores all the information about a call site needed to propagate side effects from
* one instance of {@link AmbiguatedFunctionSummary} to another.
*/
@Immutable
private static class CallSitePropagationInfo {
private CallSitePropagationInfo(
boolean allArgsUnescapedLocal, boolean calleeThisEqualsCallerThis, Token callType) {
checkArgument(NodeUtil.isInvocation(new Node(callType)), callType);
this.allArgsUnescapedLocal = allArgsUnescapedLocal;
this.calleeThisEqualsCallerThis = calleeThisEqualsCallerThis;
this.callType = callType;
}
// If all the arguments values are local to the scope in which the call site occurs.
private final boolean allArgsUnescapedLocal;
/**
* If you call a function with apply or call, one of the arguments at the call site will be used
* as 'this' inside the implementation. If this is pass into apply like so: function.apply(this,
* ...) then 'this' in the caller is tainted.
*/
private final boolean calleeThisEqualsCallerThis;
// Whether this represents CALL (not a NEW node).
private final Token callType;
/**
* Propagate the side effects from the callee to the caller.
*
* @param callee propagate from
* @param caller propagate to
* @return Returns true if the propagation changed the side effects on the caller.
*/
boolean propagate(AmbiguatedFunctionSummary callee, AmbiguatedFunctionSummary caller) {
CallSitePropagationInfo propagationType = this;
boolean changed = false;
// If the callee modifies global state then so does that caller.
if (callee.mutatesGlobalState() && !caller.mutatesGlobalState()) {
caller.setMutatesGlobalState();
changed = true;
}
// If the callee throws an exception then so does the caller.
if (callee.functionThrows() && !caller.functionThrows()) {
caller.setFunctionThrows();
changed = true;
}
// If the callee mutates its input arguments and the arguments escape the caller then it has
// unbounded side effects.
if (callee.mutatesArguments()
&& !propagationType.allArgsUnescapedLocal
&& !caller.mutatesGlobalState()) {
caller.setMutatesGlobalState();
changed = true;
}
if (callee.mutatesThis() && propagationType.calleeThisEqualsCallerThis) {
if (!caller.mutatesThis()) {
caller.setMutatesThis();
changed = true;
}
} else if (callee.mutatesThis() && propagationType.callType != Token.NEW) {
// NEW invocations of a constructor that modifies "this" don't cause side effects.
if (!caller.mutatesGlobalState()) {
caller.setMutatesGlobalState();
changed = true;
}
}
return changed;
}
static CallSitePropagationInfo computePropagationType(Node callSite) {
checkArgument(NodeUtil.isInvocation(callSite), callSite);
boolean thisIsOuterThis = false;
if (isCallOrTaggedTemplateLit(callSite)) {
// Side effects only propagate via regular calls.
// Calling a constructor that modifies "this" has no side effects.
// Notice that we're using "mutatesThis" from the callee
// summary. If the call site is actually a .call or .apply, then
// the "this" is going to be one of its arguments.
boolean isCallOrApply = isCallOrApply(callSite);
Node objectNode = isCallOrApply ? callSite.getSecondChild() : callSite.getFirstFirstChild();
if (objectNode != null && objectNode.isName() && !isCallOrApply) {
// Exclude ".call" and ".apply" as the value may still be
// null or undefined. We don't need to worry about this with a
// direct method call because null and undefined don't have any
// properties.
// TODO(nicksantos): Turn this back on when locals-tracking
// is fixed. See testLocalizedSideEffects11.
//if (!caller.knownLocals.contains(name)) {
//}
} else if (objectNode != null && objectNode.isThis()) {
thisIsOuterThis = true;
}
}
boolean argsUnescapedLocal = NodeUtil.allArgsUnescapedLocal(callSite);
return new CallSitePropagationInfo(argsUnescapedLocal, thisIsOuterThis, callSite.getToken());
}
}
/**
* A summary for the set of functions that share a particular name.
*
* Side-effects of the functions are the most significant aspect of this summary. Because the
* functions are "ambiguated", the recorded side-effects are the union of all side effects
* detected in any member of the set.
*
*
Name in this context refers to a short name, not a qualified name; only the last segment of
* a qualified name is used.
*/
private static final class AmbiguatedFunctionSummary {
// Side effect types:
private static final int THROWS = 1 << 1;
private static final int MUTATES_GLOBAL_STATE = 1 << 2;
private static final int MUTATES_THIS = 1 << 3;
private static final int MUTATES_ARGUMENTS = 1 << 4;
// Function metatdata
private static final int ESCAPED_RETURN = 1 << 5;
// The name shared by the set of functions that defined this summary.
private final String name;
// The node holding this summary in the reverse call graph.
private final DiGraphNode graphNode;
// The side effect flags for this set of functions.
// TODO(nickreid): Replace this with a `Node.SideEffectFlags`.
private int bitmask = 0;
/** Adds a new summary node to {@code graph}, storing the node and returning the summary. */
static AmbiguatedFunctionSummary createInGraph(
DiGraph graph, String name) {
return new AmbiguatedFunctionSummary(graph, name);
}
private AmbiguatedFunctionSummary(
DiGraph graph, String name) {
this.name = checkNotNull(name);
this.graphNode = graph.createDirectedGraphNode(this);
}
private void setMask(int mask) {
bitmask |= mask;
}
private boolean getMask(int mask) {
return (bitmask & mask) != 0;
}
boolean mutatesThis() {
return getMask(MUTATES_THIS);
}
/** Marks the function as having "modifies this" side effects. */
void setMutatesThis() {
setMask(MUTATES_THIS);
}
/**
* Returns whether the function returns something that is not affected by global state.
*
* In the current implementation, this is only true if the return value is a literal or
* primitive since locals are not tracked correctly.
*/
boolean escapedReturn() {
return getMask(ESCAPED_RETURN);
}
/** Marks the function as having non-local return result. */
void setEscapedReturn() {
setMask(ESCAPED_RETURN);
}
/** Returns true if function has an explicit "throw". */
boolean functionThrows() {
return getMask(THROWS);
}
/** Marks the function as having "throw" side effects. */
void setFunctionThrows() {
setMask(THROWS);
}
/** Returns true if function mutates global state. */
boolean mutatesGlobalState() {
return getMask(MUTATES_GLOBAL_STATE);
}
/** Marks the function as having "modifies globals" side effects. */
void setMutatesGlobalState() {
setMask(MUTATES_GLOBAL_STATE);
}
/** Returns true if function mutates its arguments. */
boolean mutatesArguments() {
return getMask(MUTATES_GLOBAL_STATE | MUTATES_ARGUMENTS);
}
/** Marks the function as having "modifies arguments" side effects. */
void setMutatesArguments() {
setMask(MUTATES_ARGUMENTS);
}
@Override
@DoNotCall // For debugging only.
public String toString() {
return MoreObjects.toStringHelper(getClass())
.add("name", name)
.add("graphNode", graphNode)
.add("sideEffects", sideEffectsToString())
.toString();
}
private String sideEffectsToString() {
List status = new ArrayList<>();
if (mutatesThis()) {
status.add("this");
}
if (mutatesGlobalState()) {
status.add("global");
}
if (mutatesArguments()) {
status.add("args");
}
if (escapedReturn()) {
status.add("return");
}
if (functionThrows()) {
status.add("throw");
}
return status.toString();
}
/** Update function for @nosideeffects annotations. */
private void updateSideEffectsFromExtern(Node externFunction, AbstractCompiler compiler) {
checkArgument(externFunction.isFunction());
checkArgument(externFunction.isFromExterns());
JSDocInfo info = NodeUtil.getBestJSDocInfo(externFunction);
// Handle externs.
JSType typei = externFunction.getJSType();
FunctionType functionType = typei == null ? null : typei.toMaybeFunctionType();
if (functionType == null) {
// Assume extern functions return tainted values when we have no type info to say otherwise.
setEscapedReturn();
} else {
JSType retType = functionType.getReturnType();
if (!PureFunctionIdentifier.isLocalValueType(retType, compiler)) {
setEscapedReturn();
}
}
if (info == null) {
// We don't know anything about this function so we assume it has side effects.
setMutatesGlobalState();
setFunctionThrows();
} else {
if (info.modifiesThis()) {
setMutatesThis();
} else if (info.hasSideEffectsArgumentsAnnotation()) {
setMutatesArguments();
} else if (!info.getThrownTypes().isEmpty()) {
setFunctionThrows();
} else if (info.isNoSideEffects()) {
// Do nothing.
} else {
setMutatesGlobalState();
}
}
}
}
/**
* TODO: This could be greatly improved.
*
* @return Whether the jstype is something known to be a local value.
*/
private static boolean isLocalValueType(JSType typei, AbstractCompiler compiler) {
checkNotNull(typei);
JSType nativeObj = compiler.getTypeRegistry().getNativeType(JSTypeNative.OBJECT_TYPE);
JSType subtype = typei.meetWith(nativeObj);
// If the type includes anything related to a object type, don't assume
// anything about the locality of the value.
return subtype.isEmptyType();
}
/**
* A compiler pass that constructs a reference graph and drives the PureFunctionIdentifier across
* it.
*/
static class Driver implements CompilerPass {
private final AbstractCompiler compiler;
Driver(AbstractCompiler compiler) {
this.compiler = compiler;
}
@Override
public void process(Node externs, Node root) {
NameBasedDefinitionProvider defFinder = new NameBasedDefinitionProvider(compiler, true);
defFinder.process(externs, root);
PureFunctionIdentifier pureFunctionIdentifier =
new PureFunctionIdentifier(compiler, defFinder);
pureFunctionIdentifier.process(externs, root);
}
}
}