Problem

In src/SLNX-validator/SlnxCollector.cs at line 64, when --required-files is used with a wildcard pattern that matches zero files, the code currently emits a SLNX020 (RequiredFileDoesntExistOnSystem) error:

var matched = requiredFilesOptions.MatchedPaths;
if (matched is null || matched.Count == 0)
{
    allErrors.Add(new ValidationError(
        ValidationErrorCode.RequiredFileDoesntExistOnSystem,
        $"Required file does not exist on the system. No files matched: {requiredFilesOptions.Pattern}"));
}

The desired behaviour: when a wildcard pattern matches 0 files, this should be considered valid (no error). Zero matches with a wildcard simply means there's nothing to check — treat it the same as if --required-files was not used for that solution. Only a non-wildcard (literal) pattern that matches nothing should produce the SLNX020 error.

Wait — re-reading the request: the user actually wants 0 items to always be OK for wildcards. Specifically the change is: remove the matched.Count == 0 branch (or change it so 0 matches is not an error at all). If the glob pattern yields 0 matches, just skip the check entirely (no SLNX020 error, no reference check either).

Required changes

1. src/SLNX-validator/SlnxCollector.cs (line 61–78)

Change the logic so that 0 matched files is not an error. Instead of:

if (requiredFilesOptions is not null)
{
    var matched = requiredFilesOptions.MatchedPaths;
    if (matched is null || matched.Count == 0)
    {
        allErrors.Add(new ValidationError(
            ValidationErrorCode.RequiredFileDoesntExistOnSystem,
            $"Required file does not exist on the system. No files matched: {requiredFilesOptions.Pattern}"));
    }
    else
    {
        var hasXsdErrors = allErrors.Any(e => e.Code == ValidationErrorCode.XsdViolation);
        if (!hasXsdErrors)
        {
            allErrors.AddRange(requiredFilesChecker.CheckInSlnx(matched, slnxFile));
        }
    }
}

It should become:

if (requiredFilesOptions is not null)
{
    var matched = requiredFilesOptions.MatchedPaths;
    if (matched is not null && matched.Count > 0)
    {
        var hasXsdErrors = allErrors.Any(e => e.Code == ValidationErrorCode.XsdViolation);
        if (!hasXsdErrors)
        {
            allErrors.AddRange(requiredFilesChecker.CheckInSlnx(matched, slnxFile));
        }
    }
}

2. src/SLNX-validator/RequiredFilesOptions.cs

Update the XML doc comment for MatchedPaths to reflect that an empty list is now valid (no error):

/// <param name="MatchedPaths">
/// Absolute disk paths that were matched by <see cref="Pattern"/>.
/// An empty list means the pattern matched no files — this is not an error (no files to check).
/// <see langword="null"/> means the <c>--required-files</c> option was not used.
/// </param>

3. README.md

Update the --required-files section. The "Disk check" bullet currently says:

• Disk check — if no files match the glob patterns, a SLNX020 (RequiredFileDoesntExistOnSystem) error is added to the solution result.

This should be removed or updated to reflect that 0 matches is now OK and no error is emitted. Also update the SLNX020 row in the error codes table to clarify this code is no longer triggered by wildcard zero-matches (or simply remove it if it's entirely unused — but keep it if there are still scenarios where it fires; verify this in the code).

Also update the Exit codes table under --required-files:

4. Tests

• Update tests/SLNX-validator.Tests/SlnxCollectorTests.cs: the test CollectAsync_RequiredFilesPatternNoMatch_AddsRequiredFileDoesntExistOnSystemError should be changed to assert no error (not SLNX020) when 0 files are matched, e.g. rename it to CollectAsync_RequiredFilesPatternNoMatch_NoError and assert HasErrors == false.
• Add or update any other tests that verified the SLNX020 error being emitted for zero-match glob patterns.
• If SLNX020 / RequiredFileDoesntExistOnSystem becomes entirely dead code (never emitted), consider removing it or keeping it with a note; be conservative and keep it unless it's clearly unused everywhere.

Check if SLNX020 is still used elsewhere before removing it. If it's only used in this one place (line 66 of SlnxCollector.cs), it becomes dead code and can be cleaned up, but only if you are confident it is not used anywhere else.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Bij wildcards is 0 items prima. Dus dit aanpassen inclusief docs