✨ feat(cli): add --no-capture flag for interactive programs#3777
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gaborbernat merged 3 commits intotox-dev:mainfrom Feb 19, 2026
Merged
✨ feat(cli): add --no-capture flag for interactive programs#3777gaborbernat merged 3 commits intotox-dev:mainfrom
gaborbernat merged 3 commits intotox-dev:mainfrom
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Interactive programs like Python REPL need direct terminal access to query console dimensions and handle user input. Tox normally pipes stdout/stderr for output capture, giving subprocesses pipe handles instead of console handles. This causes Python 3.13+ REPL to crash on Windows with WinError 123 when _pyrepl/windows_console.py calls Win32 APIs that require real console buffers. Add --no-capture (-i) CLI flag that makes subprocesses inherit parent console handles instead of using pipes. This is opt-in because it's mutually exclusive with result logging (--result-json) and parallel mode where output capture is essential. The flag is platform-independent since terminal APIs need console handles on all platforms, not just Windows. Validates incompatible flag combinations early with clear error messages.
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Test failures occurred because MagicMock objects return new MagicMock instances for undefined attributes, which evaluate to True. When tests accessed `env.options.no_capture` on mocked environments, this truthy mock caused subprocesses to inherit console handles instead of capturing output, breaking assertions that expected captured stdout/stderr. Explicitly set `no_capture = False` on all mock tox environments to ensure output capture behaves correctly in tests. Also updated test expectations to include the no_capture field now present in parsed options for commands that support environment arguments.
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Interactive programs like Python REPL, debuggers, and TUI applications need direct terminal access to work correctly. They query console dimensions, set raw mode for keystroke input, and send VT100 escape sequences for cursor control. 🐛 Tox normally pipes stdout/stderr to capture output for logging and result reporting, but this breaks terminal APIs that require real console handles instead of pipe handles. Python 3.13+ REPL crashes on Windows with
WinError 123when_pyrepl/windows_console.pytries to call Win32 APIs that only work on console buffers, and similar failures occur on other platforms when programs try to query terminal properties.The new
--no-capture(-i) flag disables output capture and makes subprocesses inherit parent console handles directly. ✨ This is opt-in because it's mutually exclusive with--result-jsonwhere output must be captured, and parallel mode where output from multiple environments would interleave. The implementation validates incompatible flag combinations early with clear error messages. Additionally,tox execnow always runs withno_captureenabled since it's designed for one-off interactive commands, and the flag is hidden from its help output to avoid confusion.The flag works on all platforms since terminal APIs universally require console handles, not just on Windows. Documentation has been added to both the how-to guide for practical usage and the explanation section to clarify why interactive terminal programs need special handling.