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update SA1518 to ignore empty (0 bytes) files #3927

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update SA1518 to ignore empty (0 bytes) files #3927

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6994273
update SA1518 to ignore empty (0 bytes) files
DWIAltonaAnalytics May 28, 2025
5b19011
move empty file check to end of check
DWIAltonaAnalytics Jun 2, 2025
f51d23e
add tests for white space only files not beeing classified as empty
DWIAltonaAnalytics Jun 2, 2025
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16 changes: 16 additions & 0 deletions StyleCop.Analyzers/StyleCop.Analyzers.Test/LayoutRules/SA1518UnitTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,22 @@ internal async Task TestWithBlankLinesAtEndOfFileAsync(OptionSetting? newlineAtE
await VerifyCSharpFixAsync(newlineAtEndOfFile, testCode, expected, fixedCode, CancellationToken.None).ConfigureAwait(false);
}

/// <summary>
/// Verifies that empty files will not produce a warning.
/// </summary>
/// <param name="newlineAtEndOfFile">The effective <see cref="OptionSetting"/> setting.</param>
/// <returns>A <see cref="Task"/> representing the asynchronous unit test.</returns>
[Theory]
[InlineData(null)]
[InlineData(OptionSetting.Allow)]
[InlineData(OptionSetting.Require)]
[InlineData(OptionSetting.Omit)]
internal async Task TestWithEmptyFileAsync(OptionSetting? newlineAtEndOfFile)
{
var testCode = string.Empty;
await VerifyCSharpDiagnosticAsync(newlineAtEndOfFile, testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
}

/// <summary>
/// Verifies that linefeed only blank lines at the end of the file will produce a warning.
/// </summary>
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8 changes: 8 additions & 0 deletions StyleCop.Analyzers/StyleCop.Analyzers/Helpers/SyntaxTreeHelpers.cs
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Expand Up @@ -72,6 +72,14 @@ public static bool IsWhitespaceOnly(this SyntaxTree tree, CancellationToken canc
&& TriviaHelper.IndexOfFirstNonWhitespaceTrivia(firstToken.LeadingTrivia) == -1;
}

public static bool IsEmpty(this SyntaxTree tree, CancellationToken cancellationToken)
{
var root = tree.GetRoot(cancellationToken);
var firstToken = root.GetFirstToken(includeZeroWidth: true);

return firstToken.IsKind(SyntaxKind.EndOfFileToken) && firstToken.FullSpan.Length == 0;
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Tests for SA1518 can be improved by checking a file with a single space or something like that. firstToken.FullSpan.Length == 0 can currently be removed without any tests failing,

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I added two test cases with white space only "files".
Of those (depending on the setting) one would fail if the IsEmpty helper does not check if the token is empty.

}

internal static bool ContainsUsingAlias(this SyntaxTree tree, ConcurrentDictionary<SyntaxTree, bool> cache)
{
if (tree == null)
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6 changes: 6 additions & 0 deletions ...eCop.Analyzers/StyleCop.Analyzers/LayoutRules/SA1518UseLineEndingsCorrectlyAtEndOfFile.cs
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Expand Up @@ -72,6 +72,12 @@ public override void Initialize(AnalysisContext context)

private static void HandleSyntaxTree(SyntaxTreeAnalysisContext context, StyleCopSettings settings)
{
if (context.Tree.IsEmpty(context.CancellationToken))
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Considering how rare this is, I would have added this check as the last thing before reporting the diagnostic, to save a couple of clock cycles when no diagnostics are reported.

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agreed and done.

{
// Empty file never contain line endings.
return;
}

var endOfFileToken = context.Tree.GetRoot().GetLastToken(includeZeroWidth: true);
TextSpan reportedSpan = new TextSpan(endOfFileToken.SpanStart, 0);

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