RegExp lookbehind tests

Tests for the stage 3 proposal at
https://tc39.github.io/proposal-regexp-lookbehind/

Tests ported from V8, written by @hashseed

test/built-ins/RegExp/lookbehind.js

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-assertion
+description: Test RegExp lookbehind
+info: |
+    The production Assertion :: (?<=Disjunction) evaluates as follows:
+      1. Evaluate Disjunction with -1 as its direction argument to obtain a Matcher m.
+      2. Return an internal Matcher closure that takes two arguments, a State x and a Continuation
+         c, and performs the following steps:
+        a. Let d be a Continuation that always returns its State argument as a successful MatchResult.
+        b. Call m(x, d) and let r be its result.
+        c. If r is failure, return failure.
+        d. Let y be r's State.
+        e. Let cap be y's captures List.
+        f. Let xe be x's endIndex.
+        g. Let z be the State (xe, cap).
+        h. Call c(z) and return its result.
+features: [regexp-lookbehind]
+includes: [compareArray.js]
+---*/
+
+// Simple fixed-length matches.
+assert.compareArray(["a"], "a".match(/^.(?<=a)/));
+assert.sameValue(null, "b".match(/^.(?<=a)/));
+assert.compareArray(["foo"], "foo1".match(/^f..(?<=.oo)/));
+assert.compareArray(["foo"], "foo2".match(/^f\w\w(?<=\woo)/));
+assert.sameValue(null, "boo".match(/^f\w\w(?<=\woo)/));
+assert.sameValue(null, "fao".match(/^f\w\w(?<=\woo)/));
+assert.sameValue(null, "foa".match(/^f\w\w(?<=\woo)/));
+assert.compareArray(["def"], "abcdef".match(/(?<=abc)\w\w\w/));
+assert.compareArray(["def"], "abcdef".match(/(?<=a.c)\w\w\w/));
+assert.compareArray(["def"], "abcdef".match(/(?<=a\wc)\w\w\w/));
+assert.compareArray(["cde"], "abcdef".match(/(?<=a[a-z])\w\w\w/));
+assert.compareArray(["def"], "abcdef".match(/(?<=a[a-z][a-z])\w\w\w/));
+assert.compareArray(["def"], "abcdef".match(/(?<=a[a-z]{2})\w\w\w/));
+assert.compareArray(["bcd"], "abcdef".match(/(?<=a{1})\w\w\w/));
+assert.compareArray(["cde"], "abcdef".match(/(?<=a{1}b{1})\w\w\w/));
+assert.compareArray(["def"], "abcdef".match(/(?<=a{1}[a-z]{2})\w\w\w/));
+
+// Variable-length matches.
+assert.compareArray(["def"], "abcdef".match(/(?<=[a|b|c]*)[^a|b|c]{3}/));
+assert.compareArray(["def"], "abcdef".match(/(?<=\w*)[^a|b|c]{3}/));
+
+// Start of line matches.
+assert.compareArray(["def"], "abcdef".match(/(?<=^abc)def/));
+assert.compareArray(["def"], "abcdef".match(/(?<=^[a-c]{3})def/));
+assert.compareArray(["def"], "xyz\nabcdef".match(/(?<=^[a-c]{3})def/m));
+assert.compareArray(["ab", "cd", "efg"], "ab\ncd\nefg".match(/(?<=^)\w+/gm));
+assert.compareArray(["ab", "cd", "efg"], "ab\ncd\nefg".match(/\w+(?<=$)/gm));
+assert.compareArray(["ab", "cd", "efg"], "ab\ncd\nefg".match(/(?<=^)\w+(?<=$)/gm));
+assert.sameValue(null, "abcdef".match(/(?<=^[^a-c]{3})def/));
+assert.sameValue(null, "foooo".match(/"^foooo(?<=^o+)$/));
+assert.sameValue(null, "foooo".match(/"^foooo(?<=^o*)$/));
+assert.compareArray(["foo"], "foo".match(/^foo(?<=^fo+)$/));
+assert.compareArray(["foooo"], "foooo".match(/^foooo(?<=^fo*)/));
+assert.compareArray(["foo", "f"], "foo".match(/^(f)oo(?<=^\1o+)$/));
+assert.compareArray(["foo", "f"], "foo".match(/^(f)oo(?<=^\1o+)$/i));
+assert.compareArray(["foo\u1234", "f"], "foo\u1234".match(/^(f)oo(?<=^\1o+).$/i));
+assert.compareArray(["def"], "abcdefdef".match(/(?<=^\w+)def/));
+assert.compareArray(["def", "def"], "abcdefdef".match(/(?<=^\w+)def/g));
+
+// Word boundary matches.
+assert.compareArray(["def"], "abc def".match(/(?<=\b)[d-f]{3}/));
+assert.compareArray(["def"], "ab cdef".match(/(?<=\B)\w{3}/));
+assert.compareArray(["def"], "ab cdef".match(/(?<=\B)(?<=c(?<=\w))\w{3}/));
+assert.sameValue(null, "abcdef".match(/(?<=\b)[d-f]{3}/));
+
+// Capturing matches.
+assert.compareArray(["def", "c"], "abcdef".match(/(?<=(c))def/));
+assert.compareArray(["def", "bc"], "abcdef".match(/(?<=(\w{2}))def/));
+assert.compareArray(["def", "bc", "c"], "abcdef".match(/(?<=(\w(\w)))def/));
+assert.compareArray(["def", "a"], "abcdef".match(/(?<=(\w){3})def/));
+assert.compareArray(["d", "bc", undefined], "abcdef".match(/(?<=(bc)|(cd))./));
+assert.compareArray(["c", "a", undefined],
+             "abcdef".match(/(?<=([ab]{1,2})\D|(abc))\w/));
+assert.compareArray(["ab", "a", "b"], "abcdef".match(/\D(?<=([ab]+))(\w)/));
+assert.compareArray(["c", "d"], "abcdef".match(/(?<=b|c)\w/g));
+assert.compareArray(["cd", "ef"], "abcdef".match(/(?<=[b-e])\w{2}/g));
+
+// Captures inside negative lookbehind. (They never capture.)
+assert.compareArray(["de", undefined], "abcdef".match(/(?<!(^|[ab]))\w{2}/));
+
+// Nested lookaround.
+assert.compareArray(["ef"], "abcdef".match(/(?<=ab(?=c)\wd)\w\w/));
+assert.compareArray(["ef", "bc"], "abcdef".match(/(?<=a(?=([^a]{2})d)\w{3})\w\w/));
+assert.compareArray(["ef", "bc"],
+             "abcdef".match(/(?<=a(?=([bc]{2}(?<!a{2}))d)\w{3})\w\w/));
+assert.sameValue(null, "abcdef".match(/(?<=a(?=([bc]{2}(?<!a*))d)\w{3})\w\w/));
+assert.compareArray(["faaa"], "faaao".match(/^faaao?(?<=^f[oa]+(?=o))/));
+
+// Back references.
+assert.compareArray(["b", "b", "bb"], "abb".match(/(.)(?<=(\1\1))/));
+assert.compareArray(["B", "B", "bB"], "abB".match(/(.)(?<=(\1\1))/i));
+assert.compareArray(["aB", "aB", "a"], "aabAaBa".match(/((\w)\w)(?<=\1\2\1)/i));
+assert.compareArray(["Ba", "Ba", "a"], "aabAaBa".match(/(\w(\w))(?<=\1\2\1)/i));
+assert.compareArray(["b", "b", "B"], "abaBbAa".match(/(?=(\w))(?<=(\1))./i));
+assert.compareArray(["foo", "'", "foo"], "  'foo'  ".match(/(?<=(.))(\w+)(?=\1)/));
+assert.compareArray(["foo", "\"", "foo"], "  \"foo\"  ".match(/(?<=(.))(\w+)(?=\1)/));
+assert.sameValue(null, "  .foo\"  ".match(/(?<=(.))(\w+)(?=\1)/));
+assert.sameValue(null, "ab".match(/(.)(?<=\1\1\1)/));
+assert.sameValue(null, "abb".match(/(.)(?<=\1\1\1)/));
+assert.compareArray(["b", "b"], "abbb".match(/(.)(?<=\1\1\1)/));
+assert.sameValue(null, "ab".match(/(..)(?<=\1\1\1)/));
+assert.sameValue(null, "abb".match(/(..)(?<=\1\1\1)/));
+assert.sameValue(null, "aabb".match(/(..)(?<=\1\1\1)/));
+assert.sameValue(null, "abab".match(/(..)(?<=\1\1\1)/));
+assert.sameValue(null, "fabxbab".match(/(..)(?<=\1\1\1)/));
+assert.sameValue(null, "faxabab".match(/(..)(?<=\1\1\1)/));
+assert.compareArray(["ab", "ab"], "fababab".match(/(..)(?<=\1\1\1)/));
+
+// Back references to captures inside the lookbehind.
+assert.compareArray(["d", "C"], "abcCd".match(/(?<=\1(\w))d/i));
+assert.compareArray(["d", "x"], "abxxd".match(/(?<=\1([abx]))d/));
+assert.compareArray(["c", "ab"], "ababc".match(/(?<=\1(\w+))c/));
+assert.compareArray(["c", "b"], "ababbc".match(/(?<=\1(\w+))c/));
+assert.sameValue(null, "ababdc".match(/(?<=\1(\w+))c/));
+assert.compareArray(["c", "abab"], "ababc".match(/(?<=(\w+)\1)c/));
+
+// Alternations are tried left to right,
+// and we do not backtrack into a lookbehind.
+assert.compareArray(["xabcd", "cd", ""], "xabcd".match(/.*(?<=(..|...|....))(.*)/));
+assert.compareArray(["xabcd", "bcd", ""], "xabcd".match(/.*(?<=(xx|...|....))(.*)/));
+assert.compareArray(["xxabcd", "bcd", ""], "xxabcd".match(/.*(?<=(xx|...))(.*)/));
+assert.compareArray(["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.
+assert.sameValue(null, "abcdbc".match(/(?<=([abc]+)).\1/));
+
+// Greedy loop.
+assert.compareArray(["c", "bbbbbb"], "abbbbbbc".match(/(?<=(b+))c/));
+assert.compareArray(["c", "b1234"], "ab1234c".match(/(?<=(b\d+))c/));
+assert.compareArray(["c", "b12b23b34"], "ab12b23b34c".match(/(?<=((?:b\d{2})+))c/));
+
+// Sticky
+var re1 = /(?<=^(\w+))def/g;
+assert.compareArray(["def", "abc"], re1.exec("abcdefdef"));
+assert.compareArray(["def", "abcdef"], re1.exec("abcdefdef"));
+var re2 = /\Bdef/g;
+assert.compareArray(["def"], re2.exec("abcdefdef"));
+assert.compareArray(["def"], re2.exec("abcdefdef"));
+
+// Misc
+assert.sameValue(null, "abcdef".match(/(?<=$abc)def/));
+assert.compareArray(["foo"], "foo".match(/^foo(?<=foo)$/));
+assert.compareArray(["foo"], "foo".match(/^f.o(?<=foo)$/));
+assert.sameValue(null, "fno".match(/^f.o(?<=foo)$/));
+assert.sameValue(null, "foo".match(/^foo(?<!foo)$/));
+assert.sameValue(null, "foo".match(/^f.o(?<!foo)$/));
+assert.compareArray(["fno"], "fno".match(/^f.o(?<!foo)$/));
+assert.compareArray(["foooo"], "foooo".match(/^foooo(?<=fo+)$/));
+assert.compareArray(["foooo"], "foooo".match(/^foooo(?<=fo*)$/));
+assert.compareArray(["abc", "abc"], /(abc\1)/.exec("abc"));
+assert.compareArray(["abc", "abc"], /(abc\1)/.exec("abc\u1234"));
+assert.compareArray(["abc", "abc"], /(abc\1)/i.exec("abc"));
+assert.compareArray(["abc", "abc"], /(abc\1)/i.exec("abc\u1234"));
+var oob_subject = "abcdefghijklmnabcdefghijklmn".substr(14);
+assert.sameValue(null, oob_subject.match(/(?=(abcdefghijklmn))(?<=\1)a/i));
+assert.sameValue(null, oob_subject.match(/(?=(abcdefghijklmn))(?<=\1)a/));
+assert.sameValue(null, "abcdefgabcdefg".substr(1).match(/(?=(abcdefg))(?<=\1)/));
+
+// Mutual recursive capture/back references
+assert.compareArray(["cacb", "a", ""], /(?<=a(.\2)b(\1)).{4}/.exec("aabcacbc"));
+assert.compareArray(["b", "ac", "ac"], /(?<=a(\2)b(..\1))b/.exec("aacbacb"));
+assert.compareArray(["x", "aa"], /(?<=(?:\1b)(aa))./.exec("aabaax"));
+assert.compareArray(["x", "aa"], /(?<=(?:\1|b)(aa))./.exec("aaaax"));

test/built-ins/RegExp/negative-lookbehind.js

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-assertion
+description: Test RegExp negative lookbehind
+info: |
+    The production Assertion :: (?<!Disjunction) evaluates as follows:
+      1. Evaluate Disjunction with -1 as its direction argument to obtain a Matcher m.
+      2. Return an internal Matcher closure that takes two arguments, a State x and a
+         Continuation c, and performs the following steps:
+        a. Let d be a Continuation that always returns its State argument as a successful
+           MatchResult.
+        b. Call m(x, d) and let r be its result.
+        c. If r is not failure, return failure.
+        d. Call c(x) and return its result.
+features: [regexp-lookbehind]
+includes: [compareArray.js]
+---*/
+
+
+// Negative lookbehind.
+assert.compareArray(["abc"], "abcdef".match(/(?<!abc)\w\w\w/));
+assert.compareArray(["abc"], "abcdef".match(/(?<!a.c)\w\w\w/));
+assert.compareArray(["abc"], "abcdef".match(/(?<!a\wc)\w\w\w/));
+assert.compareArray(["abc"], "abcdef".match(/(?<!a[a-z])\w\w\w/));
+assert.compareArray(["abc"], "abcdef".match(/(?<!a[a-z]{2})\w\w\w/));
+assert.sameValue(null, "abcdef".match(/(?<!abc)def/));
+assert.sameValue(null, "abcdef".match(/(?<!a.c)def/));
+assert.sameValue(null, "abcdef".match(/(?<!a\wc)def/));
+assert.sameValue(null, "abcdef".match(/(?<!a[a-z][a-z])def/));
+assert.sameValue(null, "abcdef".match(/(?<!a[a-z]{2})def/));
+assert.sameValue(null, "abcdef".match(/(?<!a{1}b{1})cde/));
+assert.sameValue(null, "abcdef".match(/(?<!a{1}[a-z]{2})def/));