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Keep Ruby 2.7 from warning about keywords in StdioTransport - #621
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koic merged 1 commit intoOct 17, 2026
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Since 1.8.0, `ServerSession#handle` accepts bare keyword arguments as the request (`handle(request = nil, auth_info: nil, **request_keywords)`), so `StdioTransport` passing the parsed request Hash as its only argument makes Ruby 2.7 treat the Hash as keyword arguments. The request is still handled, but every frame prints "Using the last argument as keyword parameters is deprecated" to stderr when deprecation warnings are enabled, which breaks callers that expect a silent stderr, such as RuboCop's MCP server specs on Ruby 2.7. Passing `auth_info: nil` explicitly keeps the Hash positional without changing the request that reaches the server.
koic
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Oct 16, 2026
mcp 1.8.0 makes Ruby 2.7 print a keyword argument deprecation warning for every stdio request, which fails the MCP server specs that expect a silent stderr on the Ruby 2.7 CI jobs. The fix is modelcontextprotocol/ruby-sdk#621. Excluding only 1.8.0 resolves to 1.7.0 until then and picks up 1.8.1 without another change here. mcp is a development dependency only, so users of RuboCop are not affected.
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October 17, 2026 02:51
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Since 1.8.0,
ServerSession#handleaccepts bare keyword arguments as the request (handle(request = nil, auth_info: nil, **request_keywords)), soStdioTransportpassing the parsed request Hash as its only argument makes Ruby 2.7 treat the Hash as keyword arguments. The request is still handled, but every frame prints "Using the last argument as keyword parameters is deprecated" to stderr when deprecation warnings are enabled, which breaks callers that expect a silent stderr, such as RuboCop's MCP server specs on Ruby 2.7.Passing
auth_info: nilexplicitly keeps the Hash positional without changing the request that reaches the server.Types of changes
Checklist