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Fix source generator diagnostic locations for incremental caching (#1153)

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
This commit is contained in:
Copilot 2026-01-19 09:37:15 -05:00 • committed by GitHub
commit 4a3a17da19
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2 changed files with 67 additions and 22 deletions
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44
src/ModelContextProtocol.Analyzers/XmlToDescriptionGenerator.cs
View file

@ -72,7 +72,7 @@ public sealed class XmlToDescriptionGenerator : IIncrementalGenerator
"MCP001" => Diagnostics.InvalidXmlDocumentation,
"MCP002" => Diagnostics.McpMethodMustBePartial,
_ => throw new InvalidOperationException($"Unknown diagnostic ID: {info.Id}")
}, info.Location, info.MessageArgs);
}, info.Location?.ToLocation(), info.MessageArgs);
private static IncrementalValuesProvider<MethodToGenerate> CreateProviderForAttribute(
IncrementalGeneratorInitializationContext context,
@ -108,7 +108,7 @@ public sealed class XmlToDescriptionGenerator : IIncrementalGenerator
HasGeneratableContent(xmlDocs, methodSymbol, descriptionAttribute))
{
return MethodToGenerate.CreateDiagnosticOnly(
new DiagnosticInfo("MCP002", methodDeclaration.Identifier.GetLocation(), methodSymbol.Name));
DiagnosticInfo.Create("MCP002", methodDeclaration.Identifier.GetLocation(), methodSymbol.Name));
}
return MethodToGenerate.Empty;
@ -116,7 +116,7 @@ public sealed class XmlToDescriptionGenerator : IIncrementalGenerator
// For partial methods with invalid XML, report diagnostic but still generate partial declaration.
EquatableArray<DiagnosticInfo> diagnostics = hasInvalidXml ?
new EquatableArray<DiagnosticInfo>(ImmutableArray.Create(new DiagnosticInfo("MCP001", methodSymbol.Locations.FirstOrDefault(), methodSymbol.Name))) :
new EquatableArray<DiagnosticInfo>(ImmutableArray.Create(DiagnosticInfo.Create("MCP001", methodSymbol.Locations.FirstOrDefault(), methodSymbol.Name))) :
default;
bool needsMethodDescription = xmlDocs is not null &&
@ -514,29 +514,29 @@ public sealed class XmlToDescriptionGenerator : IIncrementalGenerator
string Name,
string TypeKeyword);
/// <summary>Holds diagnostic information to be reported.</summary>
private readonly struct DiagnosticInfo
/// <summary>Holds serializable location information for incremental generator caching.</summary>
/// <remarks>
/// Roslyn <see cref="Location"/> objects cannot be stored in incremental generator cached data
/// because they contain references to syntax trees from specific compilations. Storing them
/// causes issues when the generator returns cached data with locations from earlier compilations.
/// </remarks>
private readonly record struct LocationInfo(string FilePath, TextSpan TextSpan, LinePositionSpan LineSpan)
{
public string Id { get; }
public Location? Location { get; }
public string MethodName { get; }
public static LocationInfo? FromLocation(Location? location) =>
location is null || !location.IsInSource ? null :
new LocationInfo(location.SourceTree?.FilePath ?? "", location.SourceSpan, location.GetLineSpan().Span);
public DiagnosticInfo(string id, Location? location, string methodName)
{
Id = id;
Location = location;
MethodName = methodName;
}
public Location ToLocation() =>
Location.Create(FilePath, TextSpan, LineSpan);
}
/// <summary>Holds diagnostic information to be reported.</summary>
private readonly record struct DiagnosticInfo(string Id, LocationInfo? Location, string MethodName)
{
public static DiagnosticInfo Create(string id, Location? location, string methodName) =>
new(id, LocationInfo.FromLocation(location), methodName);
public object?[] MessageArgs => [MethodName];
// For incremental generator caching, we compare only the logical content, not the Location object
public bool Equals(DiagnosticInfo other) =>
Id == other.Id && MethodName == other.MethodName;
public override bool Equals(object? obj) => obj is DiagnosticInfo other && Equals(other);
public override int GetHashCode() => (Id, MethodName).GetHashCode();
}
/// <summary>Holds extracted XML documentation for a method (used only during extraction, not cached).</summary>

45
tests/ModelContextProtocol.Analyzers.Tests/XmlToDescriptionGeneratorTests.cs
View file

@ -729,6 +729,51 @@ public partial class XmlToDescriptionGeneratorTests
Assert.Contains("invalid", diagnostic.GetMessage(), StringComparison.OrdinalIgnoreCase);
}
[Fact]
public void Generator_DiagnosticHasValidSourceLocation()
{
// This test verifies that diagnostic locations are properly reconstructed
// and point to valid source positions (regression test for locations from stale compilations)
var result = RunGenerator("""
using ModelContextProtocol.Server;
using System.ComponentModel;
namespace Test;
[McpServerToolType]
public class TestTools
{
/// <summary>
/// Test tool
/// </summary>
[McpServerTool]
public static string TestMethod(string input)
{
return input;
}
}
""", "MCP002");
Assert.True(result.Success);
// Verify the diagnostic has a valid location with correct line/column information
var diagnostic = Assert.Single(result.Diagnostics, d => d.Id == "MCP002");
Assert.NotNull(diagnostic.Location);
// Verify the location span has valid position information
var lineSpan = diagnostic.Location.GetLineSpan();
Assert.True(lineSpan.IsValid, "Diagnostic line span should be valid");
// Verify reasonable location values without assuming specific line numbers
Assert.True(lineSpan.StartLinePosition.Line >= 0, "Start line should be non-negative");
Assert.True(lineSpan.StartLinePosition.Character >= 0, "Start character should be non-negative");
Assert.True(lineSpan.EndLinePosition.Line >= lineSpan.StartLinePosition.Line, "End line should be >= start line");
// The span should have a non-zero length (the identifier "TestMethod" is 10 characters)
Assert.True(diagnostic.Location.SourceSpan.Length > 0, "Span should have non-zero length");
Assert.Equal(10, diagnostic.Location.SourceSpan.Length); // "TestMethod".Length == 10
}
[Fact]
public void Generator_WithGenericType_GeneratesCorrectly()
{