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Fix XML generator partial method issues #1059

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Merged
stephentoub merged 1 commit into from
Dec 4, 2025
+268 −2
Merged

Fix XML generator partial method issues #1059

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16 changes: 14 additions & 2 deletions src/ModelContextProtocol.Analyzers/XmlToDescriptionGenerator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -321,20 +321,25 @@ private static void AppendMethodDeclaration(
writer.WriteLine($"[return: Description(\"{EscapeString(xmlDocs.Returns)}\")]");
}

// Copy modifiers from original method syntax.
// Copy modifiers from original method syntax, excluding 'async' which is invalid on partial declarations (CS1994).
// Add return type (without nullable annotations).
// Add method name.
writer.Write(string.Join(" ", methodDeclaration.Modifiers.Select(m => m.Text)));
var modifiers = methodDeclaration.Modifiers
.Where(m => !m.IsKind(SyntaxKind.AsyncKeyword))
.Select(m => m.Text);
writer.Write(string.Join(" ", modifiers));
writer.Write(' ');
writer.Write(methodSymbol.ReturnType.ToDisplayString(SymbolDisplayFormat.MinimallyQualifiedFormat));
writer.Write(' ');
writer.Write(methodSymbol.Name);

// Add parameters with their Description attributes.
writer.Write("(");
var parameterSyntaxList = methodDeclaration.ParameterList.Parameters;
for (int i = 0; i < methodSymbol.Parameters.Length; i++)
{
IParameterSymbol param = methodSymbol.Parameters[i];
ParameterSyntax? paramSyntax = i < parameterSyntaxList.Count ? parameterSyntaxList[i] : null;

if (i > 0)
{
Expand All @@ -352,6 +357,13 @@ private static void AppendMethodDeclaration(
writer.Write(param.Type.ToDisplayString(SymbolDisplayFormat.MinimallyQualifiedFormat));
writer.Write(' ');
writer.Write(param.Name);

// Preserve default parameter values from the original syntax.
if (paramSyntax?.Default is { } defaultValue)
{
writer.Write(' ');
writer.Write(defaultValue.ToFullString().Trim());
}
}
writer.WriteLine(");");
}
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254 changes: 254 additions & 0 deletions tests/ModelContextProtocol.Analyzers.Tests/XmlToDescriptionGeneratorTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1463,6 +1463,260 @@ partial class GlobalTools
AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
}

[Fact]
public void Generator_WithDefaultParameterValues_PreservesDefaults()
{
var result = RunGenerator("""
using ModelContextProtocol.Server;
using System.ComponentModel;

namespace Test;

[McpServerToolType]
public partial class TestTools
{
/// <summary>
/// Test tool with defaults
/// </summary>
/// <param name="project">The project name</param>
/// <param name="flag">Enable flag</param>
/// <param name="count">Item count</param>
[McpServerTool]
public static partial string TestMethod(
string? project = null,
bool flag = false,
int count = 42)
{
return project ?? "default";
}
}
""");

Assert.True(result.Success);
Assert.Single(result.GeneratedSources);

var expected = $$"""
// <auto-generated/>
// ModelContextProtocol.Analyzers {{typeof(XmlToDescriptionGenerator).Assembly.GetName().Version}}

#pragma warning disable

using System.ComponentModel;
using ModelContextProtocol.Server;

namespace Test
{
partial class TestTools
{
[Description("Test tool with defaults")]
public static partial string TestMethod([Description("The project name")] string? project = null, [Description("Enable flag")] bool flag = false, [Description("Item count")] int count = 42);
}
}
""";

AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
}

[Fact]
public void Generator_WithAsyncMethod_ExcludesAsyncModifier()
{
var result = RunGenerator("""
using ModelContextProtocol.Server;
using System.ComponentModel;
using System.Threading.Tasks;

namespace Test;

[McpServerToolType]
public partial class TestTools
{
/// <summary>
/// Async tool
/// </summary>
[McpServerTool]
public async partial Task<string> DoWorkAsync(string input)
{
await Task.Delay(100);
return input;
}
}
""");

Assert.True(result.Success);
Assert.Single(result.GeneratedSources);

var expected = $$"""
// <auto-generated/>
// ModelContextProtocol.Analyzers {{typeof(XmlToDescriptionGenerator).Assembly.GetName().Version}}

#pragma warning disable

using System.ComponentModel;
using ModelContextProtocol.Server;

namespace Test
{
partial class TestTools
{
[Description("Async tool")]
public partial Task<string> DoWorkAsync(string input);
}
}
""";

AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
}

[Fact]
public void Generator_WithAsyncStaticMethod_ExcludesAsyncModifier()
{
var result = RunGenerator("""
using ModelContextProtocol.Server;
using System.ComponentModel;
using System.Threading.Tasks;

namespace Test;

[McpServerToolType]
public partial class TestTools
{
/// <summary>
/// Static async tool
/// </summary>
[McpServerTool]
public static async partial Task<string> StaticAsyncMethod(string input)
{
await Task.Delay(100);
return input;
}
}
""");

Assert.True(result.Success);
Assert.Single(result.GeneratedSources);

var expected = $$"""
// <auto-generated/>
// ModelContextProtocol.Analyzers {{typeof(XmlToDescriptionGenerator).Assembly.GetName().Version}}

#pragma warning disable

using System.ComponentModel;
using ModelContextProtocol.Server;

namespace Test
{
partial class TestTools
{
[Description("Static async tool")]
public static partial Task<string> StaticAsyncMethod(string input);
}
}
""";

AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
}

[Fact]
public void Generator_WithDefaultParameterValuesAndAsync_HandlesBothCorrectly()
{
var result = RunGenerator("""
using ModelContextProtocol.Server;
using System.ComponentModel;
using System.Threading.Tasks;

namespace Test;

[McpServerToolType]
public partial class TestTools
{
/// <summary>
/// Async tool with defaults
/// </summary>
/// <param name="input">The input</param>
/// <param name="timeout">Timeout in ms</param>
[McpServerTool]
public static async partial Task<string> AsyncWithDefaults(string input, int timeout = 1000)
{
await Task.Delay(timeout);
return input;
}
}
""");

Assert.True(result.Success);
Assert.Single(result.GeneratedSources);

var expected = $$"""
// <auto-generated/>
// ModelContextProtocol.Analyzers {{typeof(XmlToDescriptionGenerator).Assembly.GetName().Version}}

#pragma warning disable

using System.ComponentModel;
using ModelContextProtocol.Server;

namespace Test
{
partial class TestTools
{
[Description("Async tool with defaults")]
public static partial Task<string> AsyncWithDefaults([Description("The input")] string input, [Description("Timeout in ms")] int timeout = 1000);
}
}
""";

AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
}

[Fact]
public void Generator_WithStringDefaultValue_PreservesQuotedDefault()
{
var result = RunGenerator("""
using ModelContextProtocol.Server;
using System.ComponentModel;

namespace Test;

[McpServerToolType]
public partial class TestTools
{
/// <summary>
/// Test tool with string default
/// </summary>
[McpServerTool]
public static partial string TestMethod(string name = "default value")
{
return name;
}
}
""");

Assert.True(result.Success);
Assert.Single(result.GeneratedSources);

var expected = $$"""
// <auto-generated/>
// ModelContextProtocol.Analyzers {{typeof(XmlToDescriptionGenerator).Assembly.GetName().Version}}

#pragma warning disable

using System.ComponentModel;
using ModelContextProtocol.Server;

namespace Test
{
partial class TestTools
{
[Description("Test tool with string default")]
public static partial string TestMethod(string name = "default value");
}
}
""";

AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
}

private GeneratorRunResult RunGenerator([StringSyntax("C#-test")] string source)
{
var syntaxTree = CSharpSyntaxTree.ParseText(source);
Expand Down