Fix: Skip non-message SSE events in processStream

[raphaelmansuy]

Fixes #636

Problem

The StreamableClientTransport tries to JSON-decode ALL SSE events, including ping events sent by servers for keep-alive purposes. This causes errors like 'invalid character 'p' looking for beginning of value' when encountering non-JSON event data.

Solution

Modified processStream to check evt.Name and skip events that are not 'message' events (or unnamed events, which default to 'message' per SSE spec).

Changes

• Added event name check in processStream before attempting JSON decode
• Added test case for ping event filtering
• Added test for scanning multiple events including ping events

Testing

• All existing tests pass
• New tests verify ping events are properly filtered
• Tested with DeepWiki MCP server which sends ping events

[findleyr]

Thanks for the quick fix, and thorough tests!

[findleyr]

Looks like mcp/streamable_test.go is not formatted. Could you go fmt it? Thanks.

[raphaelmansuy]

Added formatting commit (SHA: 1172815). I ran ok github.com/modelcontextprotocol/go-sdk (cached)
ok github.com/modelcontextprotocol/go-sdk/auth (cached)
? github.com/modelcontextprotocol/go-sdk/examples/client/listfeatures [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/client/loadtest [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/client/middleware [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/http [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/server/basic [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/server/completion [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/server/custom-transport [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/server/distributed [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/server/elicitation [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/server/everything [no test files]
? github.com/modelcontextprotocol/go-sdk/examples/server/hello [no test files]
ok github.com/modelcontextprotocol/go-sdk/examples/server/memory (cached)
? github.com/modelcontextprotocol/go-sdk/examples/server/middleware [no test files]
ok github.com/modelcontextprotocol/go-sdk/examples/server/sequentialthinking (cached)
? github.com/modelcontextprotocol/go-sdk/examples/server/sse [no test files]
ok github.com/modelcontextprotocol/go-sdk/examples/server/toolschemas (cached)
? github.com/modelcontextprotocol/go-sdk/internal/docs [no test files]
ok github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2 (cached)
? github.com/modelcontextprotocol/go-sdk/internal/readme [no test files]
? github.com/modelcontextprotocol/go-sdk/internal/readme/client [no test files]
? github.com/modelcontextprotocol/go-sdk/internal/readme/server [no test files]
? github.com/modelcontextprotocol/go-sdk/internal/util [no test files]
? github.com/modelcontextprotocol/go-sdk/internal/xcontext [no test files]
? github.com/modelcontextprotocol/go-sdk/jsonrpc [no test files]
ok github.com/modelcontextprotocol/go-sdk/mcp (cached)
? github.com/modelcontextprotocol/go-sdk/oauthex [no test files] and all packages passed. Pushed to origin/fix/issue-636-filter-ping-events.

[raphaelmansuy]

Thanks — I formatted mcp/streamable_test.go and pushed the change (commit 1172815). I ran go test ./... and all packages passed. Please re-run CI as needed.