Add RegExp.escape methods.

Fixes 4706

Bug: http://dartbug.com/4706
Change-Id: If635cb0eb7c20405ab0127a443fe51176191b5ad
Reviewed-on: https://dart-review.googlesource.com/35641
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>

CHANGELOG.md

@@ -64,6 +64,7 @@ the assignment to `y`.
     `MINUTES_PER_DAY` to `minutesPerDay`, and
     `ZERO` to `zero`.
   * Added `Provisional` annotation to `dart:core`.
+  * Added static `escape` function to `RegExp` class.
 
 * `dart:convert`
   * `Utf8Decoder` when compiled with dart2js uses the browser's `TextDecoder` in

pkg/dev_compiler/tool/input_sdk/patch/core_patch.dart

@@ -16,7 +16,8 @@ import 'dart:_js_helper'
         NoInline,
         notNull,
         nullCheck,
-        Primitives;
+        Primitives,
+        quoteStringForRegExp;
 
 import 'dart:_runtime' as dart;
 
@@ -499,6 +500,9 @@ class RegExp {
           {bool multiLine: false, bool caseSensitive: true}) =>
       new JSSyntaxRegExp(source,
           multiLine: multiLine, caseSensitive: caseSensitive);
+
+  @patch
+  static String escape(String text) => quoteStringForRegExp(text);
 }
 
 // Patch for 'identical' function.

runtime/lib/regexp_patch.dart

@@ -37,6 +37,58 @@ class RegExp {
     return value.regexp;
   }
 
+  /**
+   * Finds the index of the first RegExp-significant char in [text].
+   *
+   * Starts looking from [start]. Returns `text.length` if no character
+   * is found that has special meaning in RegExp syntax.
+   */
+  static int _findEscapeChar(String text, int start) {
+    // Table where each character in the range U+0000 to U+007f is represented
+    // by whether it needs to be escaped in a regexp.
+    // The \x00 characters means escacped, and \x01 means non-escaped.
+    const escapes =
+        "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01"
+        "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01"
+        //                 $               (   )   *   +           .
+        "\x01\x01\x01\x01\x00\x01\x01\x01\x00\x00\x00\x00\x01\x01\x00\x01"
+        //                                                             ?
+        "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x00"
+        "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01"
+        //                                             [   \   ]   ^
+        "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x00\x00\x00\x00\x01"
+        "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01"
+        //                                             {   |   }
+        "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x00\x00\x00\x01\x01";
+    for (int i = start; i < text.length; i++) {
+      int char = text.codeUnitAt(i);
+      if (char <= 0x7f && escapes.codeUnitAt(char) == 0) return i;
+    }
+    return text.length;
+  }
+
+  @patch
+  static String escape(String text) {
+    int escapeCharIndex = _findEscapeChar(text, 0);
+    // If the text contains no characters needing escape, return it directly.
+    if (escapeCharIndex == text.length) return text;
+
+    var buffer = new StringBuffer();
+    int previousSliceEndIndex = 0;
+    do {
+      // Copy characters from previous escape to current escape into result.
+      // This includes the previously escaped character.
+      buffer.write(text.substring(previousSliceEndIndex, escapeCharIndex));
+      // Prepare the current character to be escaped by prefixing it with a '\'.
+      buffer.write(r"\");
+      previousSliceEndIndex = escapeCharIndex;
+      escapeCharIndex = _findEscapeChar(text, escapeCharIndex + 1);
+    } while (escapeCharIndex < text.length);
+    // Copy tail of string into result.
+    buffer.write(text.substring(previousSliceEndIndex, escapeCharIndex));
+    return buffer.toString();
+  }
+
   // Regular expression objects are stored in a cache of up to _MAX_CACHE_SIZE
   // elements using an LRU eviction strategy.
   // TODO(zerny): Do not impose a fixed limit on the number of cached objects.

sdk/lib/_internal/js_runtime/lib/core_patch.dart

@@ -19,6 +19,7 @@ import 'dart:_js_helper'
         objectHashCode,
         patch,
         Primitives,
+        quoteStringForRegExp,
         stringJoinUnchecked,
         getTraceFromException,
         RuntimeError;
@@ -488,6 +489,9 @@ class RegExp {
           {bool multiLine: false, bool caseSensitive: true}) =>
       new JSSyntaxRegExp(source,
           multiLine: multiLine, caseSensitive: caseSensitive);
+
+  @patch
+  static String escape(String text) => quoteStringForRegExp(text);
 }
 
 // Patch for 'identical' function.

sdk/lib/core/regexp.dart

@@ -24,11 +24,12 @@ part of dart.core;
  *
  * The following example finds all matches of a regular expression in
  * a string.
+ * ```dart
+ * RegExp exp = new RegExp(r"(\w+)");
+ * String str = "Parse my string";
+ * Iterable<Match> matches = exp.allMatches(str);
+ * ```
  *
- *     RegExp exp = new RegExp(r"(\w+)");
- *     String str = "Parse my string";
- *     Iterable<Match> matches = exp.allMatches(str);
- * 
  * Note the use of a _raw string_ (a string prefixed with `r`)
  * in the example above. Use a raw string to treat each character in a string
  * as a literal character.
@@ -43,6 +44,19 @@ abstract class RegExp implements Pattern {
   external factory RegExp(String source,
       {bool multiLine: false, bool caseSensitive: true});
 
+  /**
+   * Returns a regular expression that matches [text].
+   *
+   * If [text] contains characters that are meaningful in regular expressions,
+   * the resulting regular expression will match those characters literally.
+   * If [text] contains no characters that have special meaning in a regular
+   * expression, it is returned unmodified.
+   *
+   * The characters that have special meaning in regular expressions are:
+   * `(`, `)`, `[`, `]`, `{`, `}`, `*`, `+`, `?`, `.`, `^`, `$`, `|` and `\`.
+   */
+  external static String escape(String text);
+
   /**
    * Searches for the first match of the regular expression
    * in the string [input]. Returns `null` if there is no match.

tests/corelib_2/regexp/regexp_escape_test.dart

@@ -0,0 +1,43 @@
+// Copyright (c) 2018, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+
+var escapeChars = r"([)}{]?*+.$^|\";
+
+var nonEscapeAscii = "\x00\x01\x02\x03\x04\x05\x06\x07" //
+    "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f" //
+    "\x10\x11\x12\x13\x14\x15\x16\x17" //
+    "\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" //
+    """ !"#%&',-/0123456789:;<=>""" //
+    """@ABCDEFGHIJKLMNOPQRSTUVWXYZ_""" //
+    """`abcdefghijklmnopqrstuvwxyz~\x7f""";
+var someNonAscii =
+    new String.fromCharCodes(new List.generate(0x1000 - 128, (x) => x + 128));
+
+test(String string, [bool shouldEscape]) {
+  var escape = RegExp.escape(string);
+  Expect.isTrue(new RegExp(escape).hasMatch(string), "$escape");
+  Expect.equals(string, new RegExp(escape).firstMatch(string)[0], "$escape");
+  if (shouldEscape == true) {
+    Expect.notEquals(string, escape);
+  } else if (shouldEscape == false) {
+    Expect.equals(string, escape);
+  }
+}
+
+main() {
+  for (var c in escapeChars.split("")) {
+    test(c, true);
+  }
+  for (var c in nonEscapeAscii.split("")) {
+    test(c, false);
+  }
+  test(escapeChars, true);
+  test(nonEscapeAscii, false);
+  test(someNonAscii, false);
+  test((nonEscapeAscii + escapeChars) * 3, true);
+  test(r'.abc', true); // First only.
+  test(r'abc.', true); // Last only.
+}