fix: require status field to discriminate GetTaskResult from GetTaskPayloadResult#734
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…ayloadResult The content-based polymorphic deserializer matches GetTaskResult on the presence of "taskId" alone. This incorrectly captures GetTaskPayloadResult responses (tasks/result), which wrap arbitrary JSON and may also contain a "taskId" key but not a "status" key. Tighten the discriminator to require both "taskId" and "status", since GetTaskResult always has both fields. GetTaskPayloadResult responses (which lack "status") now correctly fall through to other deserializers or the empty result handler. Fixes modelcontextprotocol#601 Signed-off-by: Dayna Blackwell <dayna@blackwell-systems.com>
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Motivation and Context
Fixes #601
The content-based polymorphic deserializer in
selectClientResultDeserializerandselectServerResultDeserializermatchesGetTaskResulton the presence of"taskId"alone. This incorrectly capturesGetTaskPayloadResultresponses (tasks/result), which wrap arbitrary JSON and may also contain a"taskId"key but not a"status"key.When
Protocol.request<GetTaskPayloadResult>()receives a response that was deserialized asGetTaskResult, the uncheckedas Tcast at line 478 of Protocol.kt throws aClassCastException.Fix
Tighten the discriminator in both
selectClientResultDeserializerandselectServerResultDeserializerto require both"taskId"and"status", sinceGetTaskResultalways has both fields (status is required per the MCP task schema).GetTaskPayloadResultresponses (which lack"status") now correctly fall through to other deserializers or the empty result handler.How Has This Been Tested?
Added two test cases to
TasksTest:task payload result with content field is not deserialized as GetTaskResult: verifies that aCallToolResult-shaped JSON (with"content"but no"status") is correctly deserialized asCallToolResult, notGetTaskResulttask get result with status is correctly deserialized as GetTaskResult: verifies that JSON with both"taskId"and"status"is still correctly deserialized asGetTaskResultAll 37 existing tests continue to pass.
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Checklist