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Closure Compiler is a JavaScript optimizing compiler. It parses your
JavaScript, analyzes it, removes dead code and rewrites and minimizes
what's left. It also checks syntax, variable references, and types, and
warns about common JavaScript pitfalls. It is used in many of Google's
JavaScript apps, including Gmail, Google Web Search, Google Maps, and
Google Docs.
/*
* Copyright 2007 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.checkState;
import static com.google.javascript.rhino.jstype.JSTypeNative.NUMBER_STRING_BOOLEAN;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import com.google.javascript.jscomp.GlobalNamespace.Name;
import com.google.javascript.jscomp.GlobalNamespace.Ref;
import com.google.javascript.jscomp.NodeTraversal.Callback;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.JSTypeExpression;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.TypeI;
import com.google.javascript.rhino.TypeIRegistry;
import java.text.MessageFormat;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;
/**
* Process variables annotated as {@code @define}. A define is
* a special constant that may be overridden by later files and
* manipulated by the compiler, much like C preprocessor {@code #define}s.
*
* @author [email protected] (Nick Santos)
*/
class ProcessDefines implements CompilerPass {
private static final Logger logger =
Logger.getLogger("com.google.javascript.jscomp.ProcessDefines");
/**
* Defines in this set will not be flagged with "unknown define" warnings. There are legacy flags
* that always set these defines, even when they might not be in the binary.
*/
private static final ImmutableSet KNOWN_DEFINES =
ImmutableSet.of("COMPILED", "goog.DEBUG");
private final AbstractCompiler compiler;
private final Map dominantReplacements;
private final boolean doReplacements;
private GlobalNamespace namespace = null;
// Warnings
static final DiagnosticType UNKNOWN_DEFINE_WARNING = DiagnosticType.warning(
"JSC_UNKNOWN_DEFINE_WARNING",
"unknown @define variable {0}");
// Errors
static final DiagnosticType INVALID_DEFINE_TYPE_ERROR =
DiagnosticType.error(
"JSC_INVALID_DEFINE_TYPE_ERROR",
"@define tag only permits literal types");
static final DiagnosticType INVALID_DEFINE_INIT_ERROR =
DiagnosticType.error(
"JSC_INVALID_DEFINE_INIT_ERROR",
"illegal initialization of @define variable {0}");
static final DiagnosticType NON_GLOBAL_DEFINE_INIT_ERROR =
DiagnosticType.error(
"JSC_NON_GLOBAL_DEFINE_INIT_ERROR",
"@define variable {0} assignment must be global");
static final DiagnosticType DEFINE_NOT_ASSIGNABLE_ERROR =
DiagnosticType.error(
"JSC_DEFINE_NOT_ASSIGNABLE_ERROR",
"@define variable {0} cannot be reassigned due to code at {1}.");
private static final MessageFormat REASON_DEFINE_NOT_ASSIGNABLE =
new MessageFormat("line {0} of {1}");
/**
* Create a pass that overrides define constants.
*
* TODO(nicksantos): Write a builder to help JSCompiler induce
* {@code replacements} from command-line flags
*
* @param replacements A hash table of names of defines to their replacements.
* All replacements must be literals.
*/
ProcessDefines(
AbstractCompiler compiler, Map replacements, boolean doReplacements) {
this.compiler = compiler;
this.dominantReplacements = replacements;
this.doReplacements = doReplacements;
}
/**
* Injects a pre-computed global namespace, so that the same namespace
* can be re-used for multiple check passes. Returns {@code this} for
* easy chaining.
*/
ProcessDefines injectNamespace(GlobalNamespace namespace) {
this.namespace = namespace;
return this;
}
@Override
public void process(Node externs, Node root) {
overrideDefines(collectDefines(externs, root));
}
private void overrideDefines(Map allDefines) {
if (doReplacements) {
for (Map.Entry def : allDefines.entrySet()) {
String defineName = def.getKey();
DefineInfo info = def.getValue();
Node inputValue = dominantReplacements.get(defineName);
Node finalValue = inputValue != null ? inputValue : info.getLastValue();
if (finalValue != info.initialValue) {
if (logger.isLoggable(Level.FINE)) {
logger.fine("Overriding @define variable " + defineName);
}
boolean changed =
finalValue.getToken() != info.initialValue.getToken()
|| !finalValue.isEquivalentTo(info.initialValue);
if (changed) {
info.initialValueParent.replaceChild(
info.initialValue, finalValue.cloneTree());
if (changed) {
compiler.reportChangeToEnclosingScope(info.initialValueParent);
}
}
}
}
}
Set unusedReplacements = Sets.difference(
dominantReplacements.keySet(), Sets.union(KNOWN_DEFINES, allDefines.keySet()));
for (String unknownDefine : unusedReplacements) {
compiler.report(JSError.make(UNKNOWN_DEFINE_WARNING, unknownDefine));
}
}
private static String format(MessageFormat format, Object... params) {
return format.format(params);
}
/**
* Only defines of literal number, string, or boolean are supported.
*/
private boolean isValidDefineType(JSTypeExpression expression) {
TypeIRegistry registry = compiler.getTypeIRegistry();
TypeI type = registry.evaluateTypeExpressionInGlobalScope(expression);
return !type.isUnknownType()
&& type.isSubtypeOf(registry.getNativeType(NUMBER_STRING_BOOLEAN));
}
/**
* Finds all defines, and creates a {@link DefineInfo} data structure for
* each one.
* @return A map of {@link DefineInfo} structures, keyed by name.
*/
Map collectDefines(Node externs, Node root) {
if (namespace == null) {
namespace = new GlobalNamespace(compiler, externs, root);
}
// Find all the global names with a @define annotation
List allDefines = new ArrayList<>();
for (Name name : namespace.getNameIndex().values()) {
Ref decl = name.getDeclaration();
if (name.docInfo != null && name.docInfo.isDefine()) {
// Process defines should not depend on check types being enabled,
// so we look for the JSDoc instead of the inferred type.
if (isValidDefineType(name.docInfo.getType())) {
allDefines.add(name);
} else {
JSError error = JSError.make(
decl.node, INVALID_DEFINE_TYPE_ERROR);
compiler.report(error);
}
} else {
for (Ref ref : name.getRefs()) {
if (ref == decl) {
// Declarations were handled above.
continue;
}
Node n = ref.node;
Node parent = ref.node.getParent();
JSDocInfo info = n.getJSDocInfo();
if (info == null &&
parent.isVar() && parent.hasOneChild()) {
info = parent.getJSDocInfo();
}
if (info != null && info.isDefine()) {
allDefines.add(name);
break;
}
}
}
}
CollectDefines pass = new CollectDefines(compiler, allDefines);
NodeTraversal.traverseRootsEs6(compiler, pass, externs, root);
return pass.getAllDefines();
}
/**
* Finds all assignments to @defines, and figures out the last value of
* the @define.
*/
private static final class CollectDefines implements Callback {
private final AbstractCompiler compiler;
private final Map assignableDefines;
private final Map allDefines;
private final Map allRefInfo;
// A hack that allows us to remove ASSIGN/VAR statements when
// we're currently visiting one of the children of the assign.
private Node lvalueToRemoveLater = null;
// A stack tied to the node traversal, to keep track of whether
// we're in a conditional block. If 1 is at the top, assignment to
// a define is allowed. Otherwise, it's not allowed.
private final Deque assignAllowed;
CollectDefines(AbstractCompiler compiler, List listOfDefines) {
this.compiler = compiler;
this.allDefines = new HashMap<>();
assignableDefines = new HashMap<>();
assignAllowed = new ArrayDeque<>();
assignAllowed.push(1);
// Create a map of references to defines keyed by node for easy lookup
allRefInfo = new HashMap<>();
for (Name name : listOfDefines) {
Ref decl = name.getDeclaration();
if (decl != null) {
allRefInfo.put(decl.node,
new RefInfo(decl, name));
}
for (Ref ref : name.getRefs()) {
if (ref == decl) {
// Declarations were handled above.
continue;
}
// If there's a TWIN def, only put one of the twins in.
if (ref.getTwin() == null || !ref.getTwin().isSet()) {
allRefInfo.put(ref.node, new RefInfo(ref, name));
}
}
}
}
/**
* Get a map of {@link DefineInfo} structures, keyed by the name of
* the define.
*/
Map getAllDefines() {
return allDefines;
}
/**
* Keeps track of whether the traversal is in a conditional branch.
* We traverse all nodes of the parse tree.
*/
@Override
public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n,
Node parent) {
updateAssignAllowedStack(n, true);
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
RefInfo refInfo = allRefInfo.get(n);
if (refInfo != null) {
Ref ref = refInfo.ref;
Name name = refInfo.name;
String fullName = name.getFullName();
switch (ref.type) {
case SET_FROM_GLOBAL:
case SET_FROM_LOCAL:
Node valParent = getValueParent(ref);
Node val = valParent.getLastChild();
if (valParent.isAssign() && name.isSimpleName() &&
name.getDeclaration() == ref) {
// For defines, it's an error if a simple name is assigned
// before it's declared
compiler.report(
t.makeError(val, INVALID_DEFINE_INIT_ERROR, fullName));
} else if (processDefineAssignment(t, fullName, val, valParent)) {
// remove the assignment so that the variable is still declared,
// but no longer assigned to a value, e.g.,
// DEF_FOO = 5; // becomes "5;"
// We can't remove the ASSIGN/VAR when we're still visiting its
// children, so we'll have to come back later to remove it.
refInfo.name.removeRef(ref);
lvalueToRemoveLater = valParent;
}
break;
default:
if (t.inGlobalHoistScope()) {
// Treat this as a reference to a define in the global scope.
// After this point, the define must not be reassigned,
// or it's an error.
DefineInfo info = assignableDefines.get(fullName);
if (info != null) {
setDefineInfoNotAssignable(info, t);
assignableDefines.remove(fullName);
}
}
break;
}
}
if (!t.inGlobalScope() &&
n.getJSDocInfo() != null && n.getJSDocInfo().isDefine()) {
// warn about @define annotations in local scopes
compiler.report(
t.makeError(n, NON_GLOBAL_DEFINE_INIT_ERROR, ""));
}
if (lvalueToRemoveLater == n) {
lvalueToRemoveLater = null;
if (n.isAssign()) {
Node last = n.getLastChild();
n.removeChild(last);
parent.replaceChild(n, last);
} else {
checkState(n.isName(), n);
n.removeFirstChild();
}
t.reportCodeChange();
}
if (n.isCall()) {
if (t.inGlobalScope()) {
// If there's a function call in the global scope,
// we just say it's unsafe and freeze all the defines.
//
// NOTE(nicksantos): We could be a lot smarter here. For example,
// ReplaceOverriddenVars keeps a call graph of all functions and
// which functions/variables that they reference, and tries
// to statically determine which functions are "safe" and which
// are not. But this would be overkill, especially because
// the intended use of defines is with config_files, where
// all the defines are at the top of the bundle.
for (DefineInfo info : assignableDefines.values()) {
setDefineInfoNotAssignable(info, t);
}
assignableDefines.clear();
}
}
updateAssignAllowedStack(n, false);
}
/**
* Determines whether assignment to a define should be allowed
* in the subtree of the given node, and if not, records that fact.
*
* @param n The node whose subtree we're about to enter or exit.
* @param entering True if we're entering the subtree, false otherwise.
*/
private void updateAssignAllowedStack(Node n, boolean entering) {
switch (n.getToken()) {
case CASE:
case FOR:
case FOR_IN:
case FUNCTION:
case HOOK:
case IF:
case SWITCH:
case WHILE:
if (entering) {
assignAllowed.push(0);
} else {
assignAllowed.remove();
}
break;
default:
break;
}
}
/**
* Determines whether assignment to a define should be allowed
* at the current point of the traversal.
*/
private boolean isAssignAllowed() {
return assignAllowed.element() == 1;
}
/**
* Tracks the given define.
*
* @param t The current traversal, for context.
* @param name The full name for this define.
* @param value The value assigned to the define.
* @param valueParent The parent node of value.
* @return Whether we should remove this assignment from the parse tree.
*/
private boolean processDefineAssignment(NodeTraversal t,
String name, Node value, Node valueParent) {
boolean fromExterns = valueParent.isFromExterns();
if (!fromExterns
&& (value == null || !NodeUtil.isValidDefineValue(value, allDefines.keySet()))) {
compiler.report(
t.makeError(value, INVALID_DEFINE_INIT_ERROR, name));
} else if (!isAssignAllowed()) {
compiler.report(
t.makeError(valueParent, NON_GLOBAL_DEFINE_INIT_ERROR, name));
} else {
DefineInfo info = allDefines.get(name);
if (info == null) {
// First declaration of this define.
info = new DefineInfo(value, valueParent);
allDefines.put(name, info);
assignableDefines.put(name, info);
} else if (info.recordAssignment(value)) {
// The define was already initialized, but this is a safe
// re-assignment.
return true;
} else {
// The define was already initialized, and this is an unsafe
// re-assignment.
compiler.report(
t.makeError(valueParent, DEFINE_NOT_ASSIGNABLE_ERROR,
name, info.getReasonWhyNotAssignable()));
}
}
return false;
}
/**
* Gets the parent node of the value for any assignment to a Name.
* For example, in the assignment
* {@code var x = 3;}
* the parent would be the NAME node.
*/
private static Node getValueParent(Ref ref) {
// there are two types of declarations: VARs, ASSIGNs, and CONSTs
return ref.node.getParent() != null &&
(ref.node.getParent().isVar() || ref.node.getParent().isConst())
? ref.node : ref.node.getParent();
}
/**
* Records the fact that because of the current node in the node traversal,
* the define can't ever be assigned again.
*
* @param info Represents the define variable.
* @param t The current traversal.
*/
private static void setDefineInfoNotAssignable(DefineInfo info, NodeTraversal t) {
info.setNotAssignable(format(REASON_DEFINE_NOT_ASSIGNABLE,
t.getLineNumber(), t.getSourceName()));
}
/**
* A simple data structure for associating a Ref with the name
* that it references.
*/
private static class RefInfo {
final Ref ref;
final Name name;
RefInfo(Ref ref, Name name) {
this.ref = ref;
this.name = name;
}
}
}
/**
* A simple class for storing information about a define.
* Gathers the initial value, the last assigned value, and whether
* the define can be safely assigned a new value.
*/
private static final class DefineInfo {
public final Node initialValueParent;
public final @Nullable Node initialValue;
private Node lastValue;
private boolean isAssignable;
private String reasonNotAssignable;
/**
* Initializes a define.
*/
public DefineInfo(@Nullable Node initialValue, Node initialValueParent) {
checkState(initialValue != null || initialValueParent.isFromExterns());
this.initialValueParent = initialValueParent;
this.initialValue = initialValue;
lastValue = initialValue;
isAssignable = true;
}
/**
* Records the fact that this define can't be assigned a value anymore.
*
* @param reason A message describing the reason why it can't be assigned.
*/
public void setNotAssignable(String reason) {
isAssignable = false;
reasonNotAssignable = reason;
}
/**
* Gets the reason why a define is not assignable.
*/
public String getReasonWhyNotAssignable() {
return reasonNotAssignable;
}
/**
* Records an assigned value.
*
* @return False if there was an error.
*/
public boolean recordAssignment(Node value) {
lastValue = value;
return isAssignable;
}
/**
* Gets the last assigned value.
*/
public Node getLastValue() {
return lastValue;
}
}
}