Tests using Cobra with ptytest can hang on macOS (and Windows) unless the output is consumed
#2122
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ptytest can hang on macOS (and Windows) unless the output is consumedptytest can hang on macOS (and Windows) unless the output is consumed
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@mafredri I updated the title to use the |
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This seems to have caused flakes on Windows, the reason could be that the input is lost due to writing to stdin before the shell is ready, or simply that the command wasn't echoed (for the same reason). We no longer need to consume the output since #2122 has been fixed, so this might remove the flake in the latter case. Ideally we would wait for the prompt to be present, but since we are spawning the users shell, we have no control of what the prompt looks like. In CI we can make assumption but even then it could change in the future.
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This seems to have caused flakes on Windows, the reason could be that the input is lost due to writing to stdin before the shell is ready, or simply that the command wasn't echoed (for the same reason). We no longer need to consume the output since #2122 has been fixed, so this might remove the flake in the latter case. Ideally we would wait for the prompt to be present, but since we are spawning the users shell, we have no control of what the prompt looks like. In CI we can make assumption but even then it could change in the future.
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Unless
ptytestoutput is consumed, a test can hang if a command outputs more than1024bytes (at least on macOS).There are two ways to work around this issue:
pty.ExpectMatch()(ensure no more than 1024 bytes are left unread)cmd.SetOut(io.Discard)insteadSince using
ptytestis a common pattern in our tests, it'd be a good idea to rewrite it so that a hang is not possible.Unless there's a bug to be fixed in underlying libraries, or changes to how ptys are configured, the most robust way to fix this would be for
ptytestto buffer/consume all command output, irregardless of a call toExpectMatch.A reproduction of this bug exists as a test in #1629 (and will be merged in and skipped on macOS and Windows).
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