fix(jsonrpc2): decode requests when method key is present#999
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Use json.RawMessage for the method field so DecodeMessage can distinguish a missing method key from an explicitly empty method string. Fixes the silent stdio drop in modelcontextprotocol#976 with a single JSON parse (no second fields-map unmarshal). Fixes modelcontextprotocol#976
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Superseded by a clean branch with a single commit. |
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Summary
Fixes #976.
DecodeMessageusedmsg.Method != ""to classify messages. A wire payload with"method":""was decoded as a response, so stdio servers dropped it without a correlated JSON-RPC error.Approach
Decode into a
wireDecodestruct whosemethodfield isjson.RawMessage. Treat the message as a request when themethodkey is present on the wire (including""), which matches JSON-RPC semantics.This revision:
json.RawMessageis used formethodmethodkey stay on the response pathTest plan
go test ./internal/jsonrpc2/... -vgo test ./mcp/... -run TestIOConnRead_EmptyMethod -vgo test ./... -count=1go test -race ./internal/jsonrpc2/... -count=1npx @modelcontextprotocol/conformance server --url http://127.0.0.1:3000/mcp) — 40 passed, 0 failed./scripts/client-conformance.sh) — 217 passed, 0 failedScope note
This PR addresses the primary repro in #976 (empty
methodwith validid). Other cases listed in the issue (id: null, structurally invalid envelopes) are unchanged.