LibTest/core/RegExp/Pattern_semantics/firstMatch_Term_A04_t01.dart

// Copyright (c) 2011, 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.

/// @assertion 15.10.2.5: Once the minimum number of repetitions has been
/// satisfied, any more expansions of Atom that match the empty String are not
/// considered for further repetitions. This prevents the regular expression
/// engine from falling into an infinite loop on certain patterns.
/// @description Checks that the infinite loops are indeed avoided (no stack
/// overflow or other errors occur).
/// @author rodionov

import "../../../../Utils/expect.dart";
 
main() {
  check(r"(a*)b\1+", "baaaac", ["b", ""]);
  check(r"(a*)*", "b", ["", null]);
}

void check(String pattern, String str, List<String?> expectedGroups) {
  RegExp re = new RegExp(pattern);
  Expect.isNotNull(re.firstMatch(str));
  Match fm = re.firstMatch(str) as Match;
  if(null == fm) {
    Expect.fail("\"$pattern\" !~ \"$str\"");
  }
  if(null != expectedGroups) {
    Expect.equals(expectedGroups.length, fm.groupCount + 1);
    
    for(int i = 0; i <= fm.groupCount; i++) {
      String? expGr = expectedGroups[i];
      String? actGr = fm.group(i);
      Expect.equals(expGr, actGr,
          "Mismatch at group $i: \"$expGr\" expected instead of \"$actGr\"");
    }
  }
}