v8/test/mjsunit/es6/unicode-regexp-zero-length.js

// Copyright 2016 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.

var L = "\ud800";
var T = "\udc00";
var x = "x";

var r = /()/g;  // Global, but not unicode.
// Zero-length matches do not advance lastIndex.
assertEquals(["", ""], r.exec(L + T + L + T));
assertEquals(0, r.lastIndex);
r.lastIndex = 1;
assertEquals(["", ""], r.exec(L + T + L + T));
assertEquals(1, r.lastIndex);

var u = /()/ug;  // Global and unicode.
// Zero-length matches do not advance lastIndex.
assertEquals(["", ""], u.exec(L + T + L + T));
assertEquals(0, u.lastIndex);
u.lastIndex = 1;
assertEquals(["", ""], u.exec(L + T + L + T));
assertEquals(0, u.lastIndex);

// However, with repeating matches, lastIndex does not matter.
// We do advance from match to match.
r.lastIndex = 2;
assertEquals(x + L + x + T + x + L + x + T + x,
             (L + T + L + T).replace(r, "x"));

// With unicode flag, we advance code point by code point.
u.lastIndex = 3;
assertEquals(x + L + T + x + L + T + x,
             (L + T + L + T).replace(u, "x"));

// Test that exhausting the global match cache is fine.
assertEquals((x + L + T).repeat(1000) + x,
             (L + T).repeat(1000).replace(u, "x"));

// Same thing for RegExp.prototype.match.
r.lastIndex = 1;
assertEquals(["","","","",""], (L + T + L + T).match(r));
r.lastIndex = 2;
assertEquals(["","","","",""], (L + T + L + T).match(r));

u.lastIndex = 1;
assertEquals(["","",""], (L + T + L + T).match(u));
u.lastIndex = 2;
assertEquals(["","",""], (L + T + L + T).match(u));

var expected = [];
for (var i = 0; i <= 1000; i++) expected.push("");
assertEquals(expected, (L + T).repeat(1000).match(u));

// Also test RegExp.prototype.@@split.
assertEquals(["\u{12345}"], "\u{12345}".split(/(?:)/u));