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/*
* Copyright 2015 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.javascript.jscomp.NodeTraversal.ExternsSkippingCallback;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.JSDocInfo.Visibility;
import com.google.javascript.rhino.Node;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
/**
* Inline constant aliases
*
* This pass was originally necessary because typechecking did not handle type aliases well. Now
* typechecking understands type aliases. In theory, this pass can be deleted, but in practice this
* pass affects some check passes that run post-typechecking.
*
*
This alias inliner is not very aggressive. It will only inline explicitly const aliases but
* not effectively const ones (for example ones that are only ever assigned a value once). This is
* done to be conservative since it's not a good idea to be making dramatic AST changes during
* checks (or really, any AST changes at all). There is a more aggressive alias inliner that runs at
* the start of optimization.
*
*
TODO(b/124915436): Delete this pass.
*/
final class InlineAliases implements CompilerPass {
static final DiagnosticType ALIAS_CYCLE =
DiagnosticType.error("JSC_ALIAS_CYCLE", "Alias path contains a cycle: {0} to {1}");
private final AbstractCompiler compiler;
private final Map aliases = new LinkedHashMap<>();
private GlobalNamespace namespace;
private final AstFactory astFactory;
InlineAliases(AbstractCompiler compiler) {
this.compiler = compiler;
this.astFactory = compiler.createAstFactory();
}
@Override
public void process(Node externs, Node root) {
namespace = new GlobalNamespace(compiler, externs, root);
NodeTraversal.traverseRoots(compiler, new AliasesCollector(), externs, root);
NodeTraversal.traverseRoots(compiler, new AliasesInliner(), externs, root);
}
private class AliasesCollector extends ExternsSkippingCallback {
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case VAR:
case CONST:
case LET:
if (n.hasOneChild() && t.inGlobalScope()) {
visitAliasDefinition(n.getFirstChild(), NodeUtil.getBestJSDocInfo(n.getFirstChild()));
}
break;
case ASSIGN:
if (parent != null && parent.isExprResult() && t.inGlobalScope()) {
visitAliasDefinition(n.getFirstChild(), n.getJSDocInfo());
}
break;
default:
break;
}
}
/**
* Maybe record that given lvalue is an alias of the qualified name on its rhs.
* Note that since we are doing a post-order traversal, any previous aliases contained in
* the rhs will have already been substituted by the time we record the new alias.
*/
private void visitAliasDefinition(Node lhs, JSDocInfo info) {
if (isDeclaredConst(lhs, info) && (info == null || !info.hasTypeInformation())
&& lhs.isQualifiedName()) {
Node rhs = NodeUtil.getRValueOfLValue(lhs);
if (rhs != null && rhs.isQualifiedName()) {
GlobalNamespace.Name lhsName = namespace.getOwnSlot(lhs.getQualifiedName());
GlobalNamespace.Name rhsName = namespace.getOwnSlot(rhs.getQualifiedName());
if (lhsName != null
&& lhsName.calculateInlinability().shouldInlineUsages()
&& rhsName != null
&& rhsName.calculateInlinability().shouldInlineUsages()
&& !isPrivate(rhsName.getDeclaration().getNode())) {
aliases.put(lhs.getQualifiedName(), rhs.getQualifiedName());
}
}
}
}
private boolean isDeclaredConst(Node lhs, JSDocInfo info) {
if (info != null && info.hasConstAnnotation()) {
return true;
}
return lhs.getParent().isConst();
}
private boolean isPrivate(Node nameNode) {
if (nameNode.isQualifiedName()
&& compiler.getCodingConvention().isPrivate(nameNode.getQualifiedName())) {
return true;
}
JSDocInfo info = NodeUtil.getBestJSDocInfo(nameNode);
return info != null && info.getVisibility().equals(Visibility.PRIVATE);
}
}
private class AliasesInliner extends ExternsSkippingCallback {
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case NAME:
case GETPROP:
if (n.isQualifiedName() && aliases.containsKey(n.getQualifiedName())) {
if (isLeftmostNameLocal(t, n)) {
// The alias is shadowed by a local variable. Don't rewrite.
return;
}
if (NodeUtil.isNameDeclOrSimpleAssignLhs(n, parent)) {
// The node defines an alias. Don't rewrite.
return;
}
Node newNode =
astFactory.createQName(t.getScope(), resolveAlias(n.getQualifiedName(), n));
if (isLeftmostNameLocal(t, newNode)) {
// The aliased name is shadowed by a local variable. Don't rewrite.
return;
}
// If n is get_prop like "obj.foo" then newNode should use only location of foo, not
// obj.foo.
newNode.useSourceInfoFromForTree(n.isGetProp() ? n.getLastChild() : n);
// Similarly if n is get_prop like "obj.foo" we should index only foo. obj should not
// be indexed as it's invisible to users.
if (newNode.isGetProp()) {
newNode.getFirstChild().makeNonIndexableRecursive();
}
parent.replaceChild(n, newNode);
t.reportCodeChange();
}
break;
default:
break;
}
}
private boolean isLeftmostNameLocal(NodeTraversal t, Node n) {
Preconditions.checkState(n.isQualifiedName());
String leftmostName = NodeUtil.getRootOfQualifiedName(n).getString();
Var v = t.getScope().getVar(leftmostName);
return v != null && v.isLocal();
}
/**
* Use the alias table to look up the resolved name of the given alias. If the result is also an
* alias repeat until the real name is resolved.
* @param n
*/
private String resolveAlias(String name, Node n) {
Set aliasPath = new LinkedHashSet<>();
while (aliases.containsKey(name)) {
if (!aliasPath.add(name)) {
compiler.report(JSError.make(n, ALIAS_CYCLE, aliasPath.toString(), name));
// Cut the cycle so that it doesn't get reported more than once.
aliases.remove(name);
break;
}
name = aliases.get(name);
}
return name;
}
}
}