tests/corelib/regexp/unicode-regexp-zero-length_test.dart

// Copyright (c) 2019, the Dart project authors. All rights reserved.
// Copyright 2016 the V8 project authors. All rights reserved.
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import 'package:expect/expect.dart';

import 'v8_regexp_utils.dart';

void main() {
  const L = "\ud800";
  const T = "\udc00";
  const x = "x";

  var r = RegExp(r"()"); // Not unicode.
  // Zero-length matches do not advance lastIndex.
  var m = r.matchAsPrefix(L + T + L + T)!;
  shouldBe(m, ["", ""]);
  assertEquals(0, m.end);

  m = r.matchAsPrefix(L + T + L + T, 1)!;
  shouldBe(m, ["", ""]);
  assertEquals(1, m.end);

  var u = RegExp(r"()", unicode: true);

  // Zero-length matches do not advance lastIndex (but do respect paired
  // surrogates).
  m = u.matchAsPrefix(L + T + L + T)!;
  shouldBe(m, ["", ""]);
  assertEquals(0, m.end);

  m = u.matchAsPrefix(L + T + L + T, 1)!;
  shouldBe(m, ["", ""]);
  assertEquals(0, m.end);

  // However, with repeating matches, we do advance from match to match.
  var ms = r.allMatches(L + T + L + T);
  assertEquals(5, ms.length);
  for (var i = 0; i < ms.length; i++) {
    shouldBe(ms.elementAt(i), ["", ""]);
  }

  // With unicode flag, we advance code point by code point.
  ms = u.allMatches(L + T + L + T);
  assertEquals(3, ms.length);
  for (var i = 0; i < ms.length; i++) {
    shouldBe(ms.elementAt(i), ["", ""]);
  }

  // Test with a lot of copies.
  const c = 100;
  ms = u.allMatches((L + T) * c);
  assertEquals(c + 1, ms.length);
  for (var i = 0; i < ms.length; i++) {
    shouldBe(ms.elementAt(i), ["", ""]);
  }

  // Same with replaceAll().
  assertEquals(
      x + L + x + T + x + L + x + T + x, (L + T + L + T).replaceAll(r, "x"));

  assertEquals(x + L + T + x + L + T + x, (L + T + L + T).replaceAll(u, "x"));

  assertEquals((x + L + T) * c + x, ((L + T) * c).replaceAll(u, "x"));

  // Also test String#split.
  Expect.deepEquals(
      ["\u{12345}"], "\u{12345}".split(RegExp(r"(?:)", unicode: true)));
}