Experimental support for RegExp lookbehind.

test/mjsunit/harmony/regexp-lookbehind.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-regexp-lookbehind
+
+// Simple fixed-length matches.
+assertEquals(["a"], "a".match(/^.(?<=a)/));
+assertNull("b".match(/^.(?<=a)/));
+assertEquals(["foo"], "foo1".match(/^f..(?<=.oo)/));
+assertEquals(["foo"], "foo2".match(/^f\w\w(?<=\woo)/));
+assertNull("boo".match(/^f\w\w(?<=\woo)/));
+assertNull("fao".match(/^f\w\w(?<=\woo)/));
+assertNull("foa".match(/^f\w\w(?<=\woo)/));
+assertEquals(["def"], "abcdef".match(/(?<=abc)\w\w\w/));
+assertEquals(["def"], "abcdef".match(/(?<=a.c)\w\w\w/));
+assertEquals(["def"], "abcdef".match(/(?<=a\wc)\w\w\w/));
+assertEquals(["cde"], "abcdef".match(/(?<=a[a-z])\w\w\w/));
+assertEquals(["def"], "abcdef".match(/(?<=a[a-z][a-z])\w\w\w/));
+assertEquals(["def"], "abcdef".match(/(?<=a[a-z]{2})\w\w\w/));
+assertEquals(["bcd"], "abcdef".match(/(?<=a{1})\w\w\w/));
+assertEquals(["cde"], "abcdef".match(/(?<=a{1}b{1})\w\w\w/));
+assertEquals(["def"], "abcdef".match(/(?<=a{1}[a-z]{2})\w\w\w/));
+
+// Variable-length matches.
+assertEquals(["def"], "abcdef".match(/(?<=[a|b|c]*)[^a|b|c]{3}/));
+assertEquals(["def"], "abcdef".match(/(?<=\w*)[^a|b|c]{3}/));
+
+// Start of line matches.
+assertEquals(["def"], "abcdef".match(/(?<=^abc)def/));
+assertEquals(["def"], "abcdef".match(/(?<=^[a-c]{3})def/));
+assertEquals(["def"], "xyz\nabcdef".match(/(?<=^[a-c]{3})def/m));
+assertNull("abcdef".match(/(?<=^[^a-c]{3})def/));
+assertNull("foooo".match(/"^foooo(?<=^o+)$/));
+assertNull("foooo".match(/"^foooo(?<=^o*)$/));
+assertEquals(["foo"], "foo".match(/^foo(?<=^fo+)$/));
+assertEquals(["foooo"], "foooo".match(/^foooo(?<=^fo*)/));
+assertEquals(["foo", "f"], "foo".match(/^(f)oo(?<=^\1o+)$/));
+
+// Word boundary matches.
+assertEquals(["def"], "abc def".match(/(?<=\b)[d-f]{3}/));
+assertEquals(["def"], "ab cdef".match(/(?<=\B)\w{3}/));
+assertEquals(["def"], "ab cdef".match(/(?<=\B)(?<=c(?<=\w))\w{3}/));
+assertNull("abcdef".match(/(?<=\b)[d-f]{3}/));
+
+// Negative lookbehind.
+assertEquals(["abc"], "abcdef".match(/(?<!abc)\w\w\w/));
+assertEquals(["abc"], "abcdef".match(/(?<!a.c)\w\w\w/));
+assertEquals(["abc"], "abcdef".match(/(?<!a\wc)\w\w\w/));
+assertEquals(["abc"], "abcdef".match(/(?<!a[a-z])\w\w\w/));
+assertEquals(["abc"], "abcdef".match(/(?<!a[a-z]{2})\w\w\w/));
+assertNull("abcdef".match(/(?<!abc)def/));
+assertNull("abcdef".match(/(?<!a.c)def/));
+assertNull("abcdef".match(/(?<!a\wc)def/));
+assertNull("abcdef".match(/(?<!a[a-z][a-z])def/));
+assertNull("abcdef".match(/(?<!a[a-z]{2})def/));
+assertNull("abcdef".match(/(?<!a{1}b{1})cde/));
+assertNull("abcdef".match(/(?<!a{1}[a-z]{2})def/));
+
+// Capturing matches.
+assertEquals(["def", "c"], "abcdef".match(/(?<=(c))def/));
+assertEquals(["def", "bc"], "abcdef".match(/(?<=(\w{2}))def/));
+assertEquals(["def", "bc", "c"], "abcdef".match(/(?<=(\w(\w)))def/));
+assertEquals(["def", "a"], "abcdef".match(/(?<=(\w){3})def/));
+assertEquals(["d", "bc", undefined], "abcdef".match(/(?<=(bc)|(cd))./));
+assertEquals(["c", "a", undefined],
+             "abcdef".match(/(?<=([ab]{1,2})\D|(abc))\w/));
+assertEquals(["ab", "a", "b"], "abcdef".match(/\D(?<=([ab]+))(\w)/));
+assertEquals(["c", "d"], "abcdef".match(/(?<=b|c)\w/g));
+assertEquals(["cd", "ef"], "abcdef".match(/(?<=[b-e])\w{2}/g));
+
+// Captures inside negative lookbehind. (They never capture.)
+assertEquals(["de", undefined], "abcdef".match(/(?<!(^|[ab]))\w{2}/));
+
+// Nested lookaround.
+assertEquals(["ef"], "abcdef".match(/(?<=ab(?=c)\wd)\w\w/));
+assertEquals(["ef", "bc"], "abcdef".match(/(?<=a(?=([^a]{2})d)\w{3})\w\w/));
+assertEquals(["ef", "bc"],
+             "abcdef".match(/(?<=a(?=([bc]{2}(?<!a{2}))d)\w{3})\w\w/));
+assertNull("abcdef".match(/(?<=a(?=([bc]{2}(?<!a*))d)\w{3})\w\w/));
+assertEquals(["faaa"], "faaao".match(/^faaao?(?<=^f[oa]+(?=o))/));
+
+// Back references.
+assertEquals(["b", "b", "bb"], "abb".match(/(.)(?<=(\1\1))/));
+assertEquals(["B", "B", "bB"], "abB".match(/(.)(?<=(\1\1))/i));
+assertEquals(["aB", "aB", "a"], "aabAaBa".match(/((\w)\w)(?<=\1\2\1)/i));
+assertEquals(["Ba", "Ba", "a"], "aabAaBa".match(/(\w(\w))(?<=\1\2\1)/i));
+assertEquals(["b", "b", "B"], "abaBbAa".match(/(?=(\w))(?<=(\1))./i));
+assertEquals(["foo", "'", "foo"], "  'foo'  ".match(/(?<=(.))(\w+)(?=\1)/));
+assertEquals(["foo", "\"", "foo"], "  \"foo\"  ".match(/(?<=(.))(\w+)(?=\1)/));
+assertNull("  .foo\"  ".match(/(?<=(.))(\w+)(?=\1)/));
+assertNull("ab".match(/(.)(?<=\1\1\1)/));
+assertNull("abb".match(/(.)(?<=\1\1\1)/));
+assertEquals(["b", "b"], "abbb".match(/(.)(?<=\1\1\1)/));
+assertNull("ab".match(/(..)(?<=\1\1\1)/));
+assertNull("abb".match(/(..)(?<=\1\1\1)/));
+assertNull("aabb".match(/(..)(?<=\1\1\1)/));
+assertNull("abab".match(/(..)(?<=\1\1\1)/));
+assertNull("fabxbab".match(/(..)(?<=\1\1\1)/));
+assertNull("faxabab".match(/(..)(?<=\1\1\1)/));
+assertEquals(["ab", "ab"], "fababab".match(/(..)(?<=\1\1\1)/));
+
+// Back references to captures inside the lookbehind.
+assertEquals(["d", "C"], "abcCd".match(/(?<=\1(\w))d/i));
+assertEquals(["d", "x"], "abxxd".match(/(?<=\1([abx]))d/));
+assertEquals(["c", "ab"], "ababc".match(/(?<=\1(\w+))c/));
+assertEquals(["c", "b"], "ababbc".match(/(?<=\1(\w+))c/));
+assertNull("ababdc".match(/(?<=\1(\w+))c/));
+assertEquals(["c", "abab"], "ababc".match(/(?<=(\w+)\1)c/));
+
+// Alternations are tried left to right,
+// and we do not backtrack into a lookbehind.
+assertEquals(["xabcd", "cd", ""], "xabcd".match(/.*(?<=(..|...|....))(.*)/));
+assertEquals(["xabcd", "bcd", ""], "xabcd".match(/.*(?<=(xx|...|....))(.*)/));
+assertEquals(["xxabcd", "bcd", ""], "xxabcd".match(/.*(?<=(xx|...))(.*)/));
+assertEquals(["xxabcd", "xx", "abcd"], "xxabcd".match(/.*(?<=(xx|xxx))(.*)/));
+
+// We do not backtrack into a lookbehind.
+// The lookbehind captures "abc" so that \1 does not match. We do not backtrack
+// to capture only "bc" in the lookbehind.
+assertNull("abcdbc".match(/(?<=([abc]+)).\1/));
+
+// Misc
+assertNull("abcdef".match(/(?<=$abc)def/));
+assertEquals(["foo"], "foo".match(/^foo(?<=foo)$/));
+assertEquals(["foo"], "foo".match(/^f.o(?<=foo)$/));
+assertNull("fno".match(/^f.o(?<=foo)$/));
+assertNull("foo".match(/^foo(?<!foo)$/));
+assertNull("foo".match(/^f.o(?<!foo)$/));
+assertEquals(["fno"], "fno".match(/^f.o(?<!foo)$/));
+assertEquals(["foooo"], "foooo".match(/^foooo(?<=fo+)$/));
+assertEquals(["foooo"], "foooo".match(/^foooo(?<=fo*)$/));