com.google.javascript.jscomp.Normalize Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of closure-compiler Show documentation
Show all versions of closure-compiler Show documentation
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 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 com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.javascript.jscomp.AbstractCompiler.LifeCycleStage;
import com.google.javascript.jscomp.MakeDeclaredNamesUnique.BoilerplateRenamer;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.jscomp.NodeTraversal.Callback;
import com.google.javascript.jscomp.Scope.Var;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.util.Map;
import java.util.Set;
/**
* The goal with this pass is to simplify the other passes,
* by making less complex statements.
*
* Starting with statements like:
* var a = 0, b = foo();
*
* Which become:
* var a = 0;
* var b = foo();
*
* The key here is only to break down things that help the other passes
* and can be put back together in a form that is at least as small when
* all is said and done.
*
* This pass currently does the following:
* 1) Simplifies the AST by splitting var statements, moving initializiers
* out of for loops, and converting whiles to fors.
* 2) Moves hoisted functions to the top of function scopes.
* 3) Rewrites unhoisted named function declarations to be var declarations.
* 4) Makes all variable names globally unique (extern or otherwise) so that
* no value is ever shadowed (note: "arguments" may require special
* handling).
* 5) Removes duplicate variable declarations.
* 6) Marks constants with the IS_CONSTANT_NAME annotation.
*
* @author [email protected] (johnlenz)
*/
// public for ReplaceDebugStringsTest
class Normalize implements CompilerPass {
private final AbstractCompiler compiler;
private final boolean assertOnChange;
private static final boolean CONVERT_WHILE_TO_FOR = true;
static final boolean MAKE_LOCAL_NAMES_UNIQUE = true;
public static final DiagnosticType CATCH_BLOCK_VAR_ERROR =
DiagnosticType.error(
"JSC_CATCH_BLOCK_VAR_ERROR",
"The use of scope variable {0} is not allowed within a catch block " +
"with a catch exception of the same name.");
Normalize(AbstractCompiler compiler, boolean assertOnChange) {
this.compiler = compiler;
this.assertOnChange = assertOnChange;
// TODO(nicksantos): assertOnChange should only be true if the tree
// is normalized.
}
static Node parseAndNormalizeSyntheticCode(
AbstractCompiler compiler, String code, String prefix) {
Node js = compiler.parseSyntheticCode(code);
NodeTraversal.traverse(compiler, js,
new Normalize.NormalizeStatements(compiler, false));
NodeTraversal.traverse(
compiler, js,
new MakeDeclaredNamesUnique(
new BoilerplateRenamer(
compiler.getUniqueNameIdSupplier(),
prefix)));
return js;
}
static Node parseAndNormalizeTestCode(
AbstractCompiler compiler, String code, String prefix) {
Node js = compiler.parseTestCode(code);
NodeTraversal.traverse(compiler, js,
new Normalize.NormalizeStatements(compiler, false));
NodeTraversal.traverse(
compiler, js,
new MakeDeclaredNamesUnique());
return js;
}
private void reportCodeChange(String changeDescription) {
if (assertOnChange) {
throw new IllegalStateException(
"Normalize constraints violated:\n" + changeDescription);
}
compiler.reportCodeChange();
}
@Override
public void process(Node externs, Node root) {
new NodeTraversal(
compiler, new NormalizeStatements(compiler, assertOnChange))
.traverseRoots(externs, root);
if (MAKE_LOCAL_NAMES_UNIQUE) {
MakeDeclaredNamesUnique renamer = new MakeDeclaredNamesUnique();
NodeTraversal t = new NodeTraversal(compiler, renamer);
t.traverseRoots(externs, root);
}
// It is important that removeDuplicateDeclarations runs after
// MakeDeclaredNamesUnique in order for catch block exception names to be
// handled properly. Specifically, catch block exception names are
// only valid within the catch block, but our currect Scope logic
// has no concept of this and includes it in the containing function
// (or global scope). MakeDeclaredNamesUnique makes the catch exception
// names unique so that removeDuplicateDeclarations() will properly handle
// cases where a function scope variable conflict with a exception name:
// function f() {
// try {throw 0;} catch(e) {e; /* catch scope 'e'*/}
// var e = 1; // f scope 'e'
// }
// otherwise 'var e = 1' would be rewritten as 'e = 1'.
// TODO(johnlenz): Introduce a seperate scope for catch nodes.
removeDuplicateDeclarations(externs, root);
new PropagateConstantAnnotationsOverVars(compiler, assertOnChange)
.process(externs, root);
if (!compiler.getLifeCycleStage().isNormalized()) {
compiler.setLifeCycleStage(LifeCycleStage.NORMALIZED);
}
}
/**
* Propagate constant annotations over the Var graph.
*/
static class PropagateConstantAnnotationsOverVars
extends AbstractPostOrderCallback
implements CompilerPass {
private final AbstractCompiler compiler;
private final boolean assertOnChange;
PropagateConstantAnnotationsOverVars(
AbstractCompiler compiler, boolean forbidChanges) {
this.compiler = compiler;
this.assertOnChange = forbidChanges;
}
@Override
public void process(Node externs, Node root) {
new NodeTraversal(compiler, this).traverseRoots(externs, root);
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
// Note: Constant properties annotations are not propagated.
if (n.isName()) {
if (n.getString().isEmpty()) {
return;
}
JSDocInfo info = null;
// Find the JSDocInfo for a top level variable.
Var var = t.getScope().getVar(n.getString());
if (var != null) {
info = var.getJSDocInfo();
}
boolean shouldBeConstant =
(info != null && info.isConstant()) ||
NodeUtil.isConstantByConvention(
compiler.getCodingConvention(), n, parent);
boolean isMarkedConstant = n.getBooleanProp(Node.IS_CONSTANT_NAME);
if (shouldBeConstant && !isMarkedConstant) {
if (assertOnChange) {
String name = n.getString();
throw new IllegalStateException(
"Unexpected const change.\n" +
" name: "+ name + "\n" +
" parent:" + n.getParent().toStringTree());
}
n.putBooleanProp(Node.IS_CONSTANT_NAME, true);
}
}
}
}
/**
* Walk the AST tree and verify that constant names are used consistently.
*/
static class VerifyConstants extends AbstractPostOrderCallback
implements CompilerPass {
final private AbstractCompiler compiler;
final private boolean checkUserDeclarations;
VerifyConstants(AbstractCompiler compiler, boolean checkUserDeclarations) {
this.compiler = compiler;
this.checkUserDeclarations = checkUserDeclarations;
}
@Override
public void process(Node externs, Node root) {
Node externsAndJs = root.getParent();
Preconditions.checkState(externsAndJs != null);
Preconditions.checkState(externsAndJs.hasChild(externs));
NodeTraversal.traverseRoots(
compiler, Lists.newArrayList(externs, root), this);
}
private Map constantMap = Maps.newHashMap();
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (n.isName()) {
String name = n.getString();
if (n.getString().isEmpty()) {
return;
}
boolean isConst = n.getBooleanProp(Node.IS_CONSTANT_NAME);
if (checkUserDeclarations) {
boolean expectedConst = false;
CodingConvention convention = compiler.getCodingConvention();
if (NodeUtil.isConstantName(n)
|| NodeUtil.isConstantByConvention(convention, n, parent)) {
expectedConst = true;
} else {
expectedConst = false;
JSDocInfo info = null;
Var var = t.getScope().getVar(n.getString());
if (var != null) {
info = var.getJSDocInfo();
}
if (info != null && info.isConstant()) {
expectedConst = true;
} else {
expectedConst = false;
}
}
if (expectedConst) {
Preconditions.checkState(expectedConst == isConst,
"The name %s is not annotated as constant.", name);
} else {
Preconditions.checkState(expectedConst == isConst,
"The name %s should not be annotated as constant.", name);
}
}
Boolean value = constantMap.get(name);
if (value == null) {
constantMap.put(name, isConst);
} else {
Preconditions.checkState(value.booleanValue() == isConst,
"The name %s is not consistently annotated as constant.", name);
}
}
}
}
/**
* Simplify the AST:
* - VAR declarations split, so they represent exactly one child
* declaration.
* - WHILEs are converted to FORs
* - FOR loop are initializers are moved out of the FOR structure
* - LABEL node of children other than LABEL, BLOCK, WHILE, FOR, or DO are
* moved into a block.
* - Add constant annotations based on coding convention.
*/
static class NormalizeStatements implements Callback {
private final AbstractCompiler compiler;
private final boolean assertOnChange;
NormalizeStatements(AbstractCompiler compiler, boolean assertOnChange) {
this.compiler = compiler;
this.assertOnChange = assertOnChange;
}
private void reportCodeChange(String changeDescription) {
if (assertOnChange) {
throw new IllegalStateException(
"Normalize constraints violated:\n" + changeDescription);
}
compiler.reportCodeChange();
}
@Override
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
doStatementNormalizations(t, n, parent);
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getType()) {
case Token.WHILE:
if (CONVERT_WHILE_TO_FOR) {
Node expr = n.getFirstChild();
n.setType(Token.FOR);
Node empty = IR.empty();
empty.copyInformationFrom(n);
n.addChildBefore(empty, expr);
n.addChildAfter(empty.cloneNode(), expr);
reportCodeChange("WHILE node");
}
break;
case Token.FUNCTION:
normalizeFunctionDeclaration(n);
break;
case Token.NAME:
case Token.STRING:
case Token.GETTER_DEF:
case Token.SETTER_DEF:
if (!compiler.getLifeCycleStage().isNormalizedObfuscated()) {
annotateConstantsByConvention(n, parent);
}
break;
}
}
/**
* Mark names and properties that are constants by convention.
*/
private void annotateConstantsByConvention(Node n, Node parent) {
Preconditions.checkState(
n.isName()
|| n.isString()
|| n.isGetterDef()
|| n.isSetterDef());
// There are only two cases where a string token
// may be a variable reference: The right side of a GETPROP
// or an OBJECTLIT key.
boolean isObjLitKey = NodeUtil.isObjectLitKey(n, parent);
boolean isProperty = isObjLitKey ||
(parent.isGetProp() &&
parent.getLastChild() == n);
if (n.isName() || isProperty) {
boolean isMarkedConstant = n.getBooleanProp(Node.IS_CONSTANT_NAME);
if (!isMarkedConstant &&
NodeUtil.isConstantByConvention(
compiler.getCodingConvention(), n, parent)) {
if (assertOnChange) {
String name = n.getString();
throw new IllegalStateException(
"Unexpected const change.\n" +
" name: "+ name + "\n" +
" parent:" + n.getParent().toStringTree());
}
n.putBooleanProp(Node.IS_CONSTANT_NAME, true);
}
}
}
/**
* Rewrite named unhoisted functions declarations to a known
* consistent behavior so we don't to different logic paths for the same
* code. From:
* function f() {}
* to:
* var f = function () {};
*/
private void normalizeFunctionDeclaration(Node n) {
Preconditions.checkState(n.isFunction());
if (!NodeUtil.isFunctionExpression(n)
&& !NodeUtil.isHoistedFunctionDeclaration(n)) {
rewriteFunctionDeclaration(n);
}
}
/**
* Rewrite the function declaration from:
* function x() {}
* FUNCTION
* NAME
* LP
* BLOCK
* to:
* var x = function() {};
* VAR
* NAME
* FUNCTION
* NAME (w/ empty string)
* LP
* BLOCK
*/
private void rewriteFunctionDeclaration(Node n) {
// Prepare a spot for the function.
Node oldNameNode = n.getFirstChild();
Node fnNameNode = oldNameNode.cloneNode();
Node var = IR.var(fnNameNode).srcref(n);
// Prepare the function
oldNameNode.setString("");
// Move the function
Node parent = n.getParent();
parent.replaceChild(n, var);
fnNameNode.addChildToFront(n);
reportCodeChange("Function declaration");
}
/**
* Do normalizations that introduce new siblings or parents.
*/
private void doStatementNormalizations(
NodeTraversal t, Node n, Node parent) {
if (n.isLabel()) {
normalizeLabels(n);
}
// Only inspect the children of SCRIPTs, BLOCKs and LABELs, as all these
// are the only legal place for VARs and FOR statements.
if (NodeUtil.isStatementBlock(n) || n.isLabel()) {
extractForInitializer(n, null, null);
}
// Only inspect the children of SCRIPTs, BLOCKs, as all these
// are the only legal place for VARs.
if (NodeUtil.isStatementBlock(n)) {
splitVarDeclarations(n);
}
if (n.isFunction()) {
moveNamedFunctions(n.getLastChild());
}
}
// TODO(johnlenz): Move this to NodeTypeNormalizer once the unit tests are
// fixed.
/**
* Limit the number of special cases where LABELs need to be handled. Only
* BLOCK and loops are allowed to be labeled. Loop labels must remain in
* place as the named continues are not allowed for labeled blocks.
*/
private void normalizeLabels(Node n) {
Preconditions.checkArgument(n.isLabel());
Node last = n.getLastChild();
switch (last.getType()) {
case Token.LABEL:
case Token.BLOCK:
case Token.FOR:
case Token.WHILE:
case Token.DO:
return;
default:
Node block = IR.block();
block.copyInformationFrom(last);
n.replaceChild(last, block);
block.addChildToFront(last);
reportCodeChange("LABEL normalization");
return;
}
}
/**
* Bring the initializers out of FOR loops. These need to be placed
* before any associated LABEL nodes. This needs to be done from the top
* level label first so this is called as a pre-order callback (from
* shouldTraverse).
*
* @param n The node to inspect.
* @param before The node to insert the initializer before.
* @param beforeParent The parent of the node before which the initializer
* will be inserted.
*/
private void extractForInitializer(
Node n, Node before, Node beforeParent) {
for (Node next, c = n.getFirstChild(); c != null; c = next) {
next = c.getNext();
Node insertBefore = (before == null) ? c : before;
Node insertBeforeParent = (before == null) ? n : beforeParent;
switch (c.getType()) {
case Token.LABEL:
extractForInitializer(c, insertBefore, insertBeforeParent);
break;
case Token.FOR:
if (NodeUtil.isForIn(c)) {
Node first = c.getFirstChild();
if (first.isVar()) {
// Transform:
// for (var a = 1 in b) {}
// to:
// var a = 1; for (a in b) {};
Node newStatement = first;
// Clone just the node, to remove any initialization.
Node name = newStatement.getFirstChild().cloneNode();
first.getParent().replaceChild(first, name);
insertBeforeParent.addChildBefore(newStatement, insertBefore);
reportCodeChange("FOR-IN var declaration");
}
} else if (!c.getFirstChild().isEmpty()) {
Node init = c.getFirstChild();
Node empty = IR.empty();
empty.copyInformationFrom(c);
c.replaceChild(init, empty);
Node newStatement;
// Only VAR statements, and expressions are allowed,
// but are handled differently.
if (init.isVar()) {
newStatement = init;
} else {
newStatement = NodeUtil.newExpr(init);
}
insertBeforeParent.addChildBefore(newStatement, insertBefore);
reportCodeChange("FOR initializer");
}
break;
}
}
}
/**
* Split a var node such as:
* var a, b;
* into individual statements:
* var a;
* var b;
* @param n The whose children we should inspect.
*/
private void splitVarDeclarations(Node n) {
for (Node next, c = n.getFirstChild(); c != null; c = next) {
next = c.getNext();
if (c.isVar()) {
if (assertOnChange && !c.hasChildren()) {
throw new IllegalStateException("Empty VAR node.");
}
while (c.getFirstChild() != c.getLastChild()) {
Node name = c.getFirstChild();
c.removeChild(name);
Node newVar = IR.var(name).srcref(n);
n.addChildBefore(newVar, c);
reportCodeChange("VAR with multiple children");
}
}
}
}
/**
* Move all the functions that are valid at the execution of the first
* statement of the function to the beginning of the function definition.
*/
private void moveNamedFunctions(Node functionBody) {
Preconditions.checkState(
functionBody.getParent().isFunction());
Node previous = null;
Node current = functionBody.getFirstChild();
// Skip any declarations at the beginning of the function body, they
// are already in the right place.
while (current != null && NodeUtil.isFunctionDeclaration(current)) {
previous = current;
current = current.getNext();
}
// Find any remaining declarations and move them.
Node insertAfter = previous;
while (current != null) {
// Save off the next node as the current node maybe removed.
Node next = current.getNext();
if (NodeUtil.isFunctionDeclaration(current)) {
// Remove the declaration from the body.
Preconditions.checkNotNull(previous);
functionBody.removeChildAfter(previous);
// Readd the function at the top of the function body (after any
// previous declarations).
insertAfter = addToFront(functionBody, current, insertAfter);
reportCodeChange("Move function declaration not at top of function");
} else {
// Update the previous only if the current node hasn't been moved.
previous = current;
}
current = next;
}
}
/**
* @param after The child node to insert the newChild after, or null if
* newChild should be added to the front of parent's child list.
* @return The inserted child node.
*/
private Node addToFront(Node parent, Node newChild, Node after) {
if (after == null) {
parent.addChildToFront(newChild);
} else {
parent.addChildAfter(newChild, after);
}
return newChild;
}
}
/**
* Remove duplicate VAR declarations.
*/
private void removeDuplicateDeclarations(Node externs, Node root) {
Callback tickler = new ScopeTicklingCallback();
ScopeCreator scopeCreator = new SyntacticScopeCreator(
compiler, new DuplicateDeclarationHandler());
NodeTraversal t = new NodeTraversal(compiler, tickler, scopeCreator);
t.traverseRoots(externs, root);
}
/**
* ScopeCreator duplicate declaration handler.
*/
private final class DuplicateDeclarationHandler implements
SyntacticScopeCreator.RedeclarationHandler {
private Set hasOkDuplicateDeclaration = Sets.newHashSet();
/**
* Remove duplicate VAR declarations encountered discovered during
* scope creation.
*/
@Override
public void onRedeclaration(
Scope s, String name, Node n, CompilerInput input) {
Preconditions.checkState(n.isName());
Node parent = n.getParent();
Var v = s.getVar(name);
if (v != null && s.isGlobal()) {
// We allow variables to be duplicate declared if one
// declaration appears in source and the other in externs.
// This deals with issues where a browser built-in is declared
// in one browser but not in another.
if (v.isExtern() && !input.isExtern()) {
if (hasOkDuplicateDeclaration.add(v)) {
return;
}
}
}
// If name is "arguments", Var maybe null.
if (v != null && v.getParentNode().isCatch()) {
// Redeclaration of a catch expression variable is hard to model
// without support for "with" expressions.
// The EcmaScript spec (section 12.14), declares that a catch
// "catch (e) {}" is handled like "with ({'e': e}) {}" so that
// "var e" would refer to the scope variable, but any following
// reference would still refer to "e" of the catch expression.
// Until we have support for this disallow it.
// Currently the Scope object adds the catch expression to the
// function scope, which is technically not true but a good
// approximation for most uses.
// TODO(johnlenz): Consider improving how scope handles catch
// expression.
// Use the name of the var before it was made unique.
name = MakeDeclaredNamesUnique.ContextualRenameInverter.getOrginalName(
name);
compiler.report(
JSError.make(
input.getName(), n,
CATCH_BLOCK_VAR_ERROR, name));
} else if (v != null && parent.isFunction()) {
if (v.getParentNode().isVar()) {
s.undeclare(v);
s.declare(name, n, n.getJSType(), v.input);
replaceVarWithAssignment(v.getNameNode(), v.getParentNode(),
v.getParentNode().getParent());
}
} else if (parent.isVar()) {
Preconditions.checkState(parent.hasOneChild());
replaceVarWithAssignment(n, parent, parent.getParent());
}
}
/**
* Remove the parent VAR. There are three cases that need to be handled:
* 1) "var a = b;" which is replaced with "a = b"
* 2) "label:var a;" which is replaced with "label:;". Ideally, the
* label itself would be removed but that is not possible in the
* context in which "onRedeclaration" is called.
* 3) "for (var a in b) ..." which is replaced with "for (a in b)..."
* Cases we don't need to handle are VARs with multiple children,
* which have already been split into separate declarations, so there
* is no need to handle that here, and "for (var a;;);", which has
* been moved out of the loop.
* The result of this is that in each case the parent node is replaced
* which is generally dangerous in a traversal but is fine here with
* the scope creator, as the next node of interest is the parent's
* next sibling.
*/
private void replaceVarWithAssignment(Node n, Node parent, Node gramps) {
if (n.hasChildren()) {
// The * is being initialize, preserve the new value.
parent.removeChild(n);
// Convert "var name = value" to "name = value"
Node value = n.getFirstChild();
n.removeChild(value);
Node replacement = IR.assign(n, value);
replacement.copyInformationFrom(parent);
gramps.replaceChild(parent, NodeUtil.newExpr(replacement));
} else {
// It is an empty reference remove it.
if (NodeUtil.isStatementBlock(gramps)) {
gramps.removeChild(parent);
} else if (gramps.isFor()) {
// This is the "for (var a in b)..." case. We don't need to worry
// about initializers in "for (var a;;)..." as those are moved out
// as part of the other normalizations.
parent.removeChild(n);
gramps.replaceChild(parent, n);
} else {
Preconditions.checkState(gramps.isLabel());
// We should never get here. LABELs with a single VAR statement should
// already have been normalized to have a BLOCK.
throw new IllegalStateException("Unexpected LABEL");
}
}
reportCodeChange("Duplicate VAR declaration");
}
}
/**
* A simple class that causes scope to be created.
*/
private final class ScopeTicklingCallback
implements NodeTraversal.ScopedCallback {
@Override
public void enterScope(NodeTraversal t) {
// Cause the scope to be created, which will cause duplicate
// to be found.
t.getScope();
}
@Override
public void exitScope(NodeTraversal t) {
// Nothing to do.
}
@Override
public boolean shouldTraverse(
NodeTraversal nodeTraversal, Node n, Node parent) {
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
// Nothing to do.
}
}
}