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Fix Extensions not being copied to ServerCapabilities during initialization (#1399)

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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>
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Copilot 2026-02-27 19:36:15 -05:00 • committed by GitHub
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1 changed files with 93 additions and 3 deletions
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89
tests/ModelContextProtocol.Tests/Server/McpServerTests.cs
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@ -290,6 +290,95 @@ public class McpServerTests : LoggedTest
});
}
[Fact]
public async Task Initialize_IncludesExtensionsInResponse()
{
await Can_Handle_Requests(
serverCapabilities: new ServerCapabilities
{
Extensions = new Dictionary<string, object> { ["io.myext"] = new JsonObject { ["required"] = true } },
},
method: RequestMethods.Initialize,
configureOptions: null,
assertResult: (_, response) =>
{
var result = JsonSerializer.Deserialize<InitializeResult>(response, McpJsonUtilities.DefaultOptions);
Assert.NotNull(result);
Assert.NotNull(result.Capabilities.Extensions);
Assert.True(result.Capabilities.Extensions.ContainsKey("io.myext"));
});
}
[Fact]
public async Task Initialize_IncludesExperimentalInResponse()
{
await Can_Handle_Requests(
serverCapabilities: new ServerCapabilities
{
Experimental = new Dictionary<string, object> { ["customFeature"] = new JsonObject { ["enabled"] = true } },
},
method: RequestMethods.Initialize,
configureOptions: null,
assertResult: (_, response) =>
{
var result = JsonSerializer.Deserialize<InitializeResult>(response, McpJsonUtilities.DefaultOptions);
Assert.NotNull(result);
Assert.NotNull(result.Capabilities.Experimental);
Assert.True(result.Capabilities.Experimental.ContainsKey("customFeature"));
});
}
[Fact]
public async Task Initialize_CopiesAllCapabilityProperties()
{
// Set every public property on ServerCapabilities to a non-null value.
// If a new property is added to ServerCapabilities in the future but the
// server fails to copy it, this reflection-based test will automatically
// detect the missing property and fail.
var inputCapabilities = new ServerCapabilities
{
Experimental = new Dictionary<string, object> { ["test"] = new JsonObject() },
Logging = new LoggingCapability(),
Prompts = new PromptsCapability(),
Resources = new ResourcesCapability(),
Tools = new ToolsCapability(),
Completions = new CompletionsCapability(),
Tasks = new McpTasksCapability(),
Extensions = new Dictionary<string, object> { ["io.test"] = new JsonObject() },
};
await Can_Handle_Requests(
serverCapabilities: inputCapabilities,
method: RequestMethods.Initialize,
configureOptions: options =>
{
// Tasks capability requires a TaskStore
options.TaskStore = new InMemoryMcpTaskStore();
},
assertResult: (_, response) =>
{
var result = JsonSerializer.Deserialize<InitializeResult>(response, McpJsonUtilities.DefaultOptions);
Assert.NotNull(result);
// Use reflection to verify every public property on ServerCapabilities is non-null.
// This catches cases where new capability properties are added but not copied
// from options in McpServerImpl.
foreach (var property in typeof(ServerCapabilities).GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
if (!property.CanRead)
{
continue;
}
Assert.True(
property.GetValue(result.Capabilities) is not null,
$"ServerCapabilities.{property.Name} was set on options but is null in the initialize response. " +
$"Ensure the property is copied in McpServerImpl's Configure* methods.");
}
});
}
#pragma warning restore MCPEXP001
[Fact]
public async Task Can_Handle_Completion_Requests()
{