StringMatchesAssertion.patch

REQUIRED CHANGES TO: TUnit.Assertions/Conditions/StringAssertions.cs

This patch adds Match caching to StringMatchesAssertion class to enable clean, reflection-free access to regex match results.

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CHANGE 1: Add _cachedMatch field
================================================================================
Location: Line 432 (after "private RegexOptions _options = RegexOptions.None;")

ADD THIS LINE:
    private Match? _cachedMatch;

So it becomes:
    private readonly string _pattern;
    private readonly Regex? _regex;
    private RegexOptions _options = RegexOptions.None;
    private Match? _cachedMatch;  // <-- ADD THIS LINE

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CHANGE 2: Add GetMatch() method
================================================================================
Location: After line 464 (after the WithOptions() method, before CheckAsync())

ADD THIS METHOD:
    /// <summary>
    /// Gets the cached regex match result after the assertion has been executed.
    /// Returns null if the assertion hasn't been executed yet or if the match failed.
    /// </summary>
    public Match? GetMatch() => _cachedMatch;

So it becomes:
    public StringMatchesAssertion WithOptions(RegexOptions options)
    {
        _options = options;
        Context.ExpressionBuilder.Append($".WithOptions({options})");
        return this;
    }

    /// <summary>
    /// Gets the cached regex match result after the assertion has been executed.
    /// Returns null if the assertion hasn't been executed yet or if the match failed.
    /// </summary>
    public Match? GetMatch() => _cachedMatch;  // <-- ADD THIS METHOD

    protected override Task<AssertionResult> CheckAsync(EvaluationMetadata<string> metadata)
    {

================================================================================
CHANGE 3: Modify CheckAsync() to cache the Match
================================================================================
Location: Lines 486-492 in CheckAsync() method

REPLACE THIS:
        // Use the validated regex to check the match
        bool isMatch = regex.IsMatch(value);

        if (isMatch)
        {
            return Task.FromResult(AssertionResult.Passed);
        }

WITH THIS:
        // Use the validated regex to check the match and cache it
        var match = regex.Match(value);
        _cachedMatch = match;

        if (match.Success)
        {
            return Task.FromResult(AssertionResult.Passed);
        }

EXPLANATION:
- Changed from regex.IsMatch(value) to regex.Match(value) to get the Match object
- Store the Match in _cachedMatch field
- Changed from checking isMatch to checking match.Success

================================================================================
SUMMARY
================================================================================
These changes enable StringMatchesAssertionExtensions.GetMatchAsync() to work
without reflection by calling the new GetMatch() method.

The implementation follows SOLID, KISS, DRY, and SRP principles:
- Single Responsibility: StringMatchesAssertion now caches its match
- Open/Closed: API extended without modifying existing behavior
- No reflection: Clean, AOT-compatible code
- DRY: Match is performed once and cached
- KISS: Simple, straightforward implementation