Reject listRoots when client lacks roots capability - #1070
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nikita-kibitkin wants to merge 1 commit into
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Reject listRoots when client lacks roots capability#1070nikita-kibitkin wants to merge 1 commit into
nikita-kibitkin wants to merge 1 commit into
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Fail fast with an IllegalStateException instead of sending a roots/list request the client cannot handle, matching the existing guards in createMessage and createElicitation. Fixes modelcontextprotocol#1067
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Motivation and Context
Fixes #1067.
McpAsyncServerExchange.listRoots()sends aroots/listrequest even when the client did not declare the roots capability. Depending on the client, that ends in a confusing client-side error after a wire round-trip, or in a hang untilrequestTimeoutif the client ignores unknown methods.createMessage()andcreateElicitation()in the same class already fail fast on a missing capability;listRoots()was the odd one out.Description
listRoots(String cursor)now returnsMono.error(IllegalStateException)when the client is not initialized or did not declare the roots capability, without sending any request. The guard covers the no-arglistRoots()(a pagination aggregator over the cursor variant) and the sync exchange (delegates to async).McpAsyncClient: "Client must be configured with roots capabilities".How Has This Been Tested?
Four new unit tests in
McpAsyncServerExchangeTestsandMcpSyncServerExchangeTests(null capabilities and missing roots capability), each also verifying thatsendRequestis never called. All four were verified to fail without the production change.The existing
testRootsWithoutCapabilityintegration test asserted the old behavior (client-side "Roots not supported" error after the request crossed the wire); it now expects the server-side fail-fast error and asserts strictly that the call throws.Breaking Changes
None in the semver sense (bug fix aligning behavior with the sibling methods). Behavior change to be aware of: server-side callers of
listRoots()against a capability-less client now get an immediateIllegalStateExceptioninstead of a client error or a timeout.Types of changes