/*
* Copyright 2011 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.javascript.jscomp.regex.RegExpTree;
import com.google.javascript.rhino.Node;
/**
* Simplifies regular expression patterns and flags.
*
* @author Mike Samuel <mikesamuel@gmail.com>
*/
class PeepholeSimplifyRegExp extends AbstractPeepholeOptimization {
@Override
Node optimizeSubtree(Node subtree) {
if (subtree.isRegExp()) {
// Split regexp into pattern and flags.
String pattern = subtree.getFirstChild().getString();
String flags = subtree.getChildCount() == 2
? subtree.getLastChild().getString() : "";
// Parse to an AST and optimize.
RegExpTree regexTree;
try {
regexTree = RegExpTree.parseRegExp(pattern, flags);
} catch (IllegalArgumentException ex) {
// Warnings are propagated in the CheckRegExp pass.
return subtree;
}
regexTree = regexTree.simplify(flags);
// Decompose the AST.
String literal = regexTree.toString();
String newPattern = literal.substring(1, literal.length() - 1);
// Remove unnecessary flags and order them consistently for gzip.
String newFlags = (
// The g flags cannot match or replace more than one instance if it is
// anchored at the front and back as in /^foo$/ and if the anchors are
// relative to the whole string.
// But if the regex has capturing groups, then the match operator
// would return capturing groups without the g flag.
(flags.contains("g")
&& (!RegExpTree.matchesWholeInput(regexTree, flags)
|| regexTree.hasCapturingGroup())
? "g" : "")
// Remove the i flag if it doesn't have any effect.
// E.g. /[a-z0-9_]/i -> /\w/
+ (flags.contains("i") && regexTree.isCaseSensitive() ? "i" : "")
// If the regular expression contains no anchors, then the m flag has
// no effect.
+ (flags.contains("m") && regexTree.containsAnchor() ? "m" : ""));
// Update the original if something was done.
if (!(newPattern.equals(pattern) && newFlags.equals(flags))) {
subtree.getFirstChild().setString(newPattern);
if (!newFlags.isEmpty()) {
subtree.getLastChild().setString(newFlags);
} else if (subtree.getChildCount() == 2) {
subtree.getLastChild().detachFromParent();
}
reportCodeChange();
}
}
return subtree;
}
}