fix: widen errlog type to accept subprocess.DEVNULL#2318
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Bortlesboat wants to merge 1 commit intomodelcontextprotocol:mainfrom
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fix: widen errlog type to accept subprocess.DEVNULL#2318Bortlesboat wants to merge 1 commit intomodelcontextprotocol:mainfrom
Bortlesboat wants to merge 1 commit intomodelcontextprotocol:mainfrom
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The errlog parameter in stdio_client and related functions was typed as TextIO, which prevented passing subprocess.DEVNULL (an int) to suppress stderr output from MCP server subprocesses. Both subprocess.Popen and anyio.open_process already accept int values for stderr, so widening the type to TextIO | int is safe. Github-Issue: #1806 Reported-by: sesajad
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Closes #1806
Summary
Widens the
errlogparameter type instdio_clientand the internal process creation helpers fromTextIOtoTextIO | int. This allows passingsubprocess.DEVNULL(which isintvalue-3) to suppress stderr output from MCP server subprocesses.Motivation
Users who want to suppress stderr output from their MCP server subprocesses currently can't pass
subprocess.DEVNULLbecause the type hint restricts toTextIO. Bothsubprocess.Popenandanyio.open_processalready acceptintvalues for theirstderrparameter, so widening the type is safe and aligns with the underlying APIs.Changes
stdio_client():errlog: TextIO→errlog: TextIO | int_create_platform_compatible_process():errlog: TextIO→errlog: TextIO | intcreate_windows_process():errlog: TextIO | None→errlog: TextIO | int | None_create_windows_fallback_process():errlog: TextIO | None→errlog: TextIO | int | NoneTest plan
src/mcp/client/stdio.pysubprocess.DEVNULLis now accepted without type errors