_subprocess: Fix pip install log window not showing
#567
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woodruffw
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Mar 31, 2023
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| * Fixed an issue where the log window that we use to display `pip-audit`'s | ||
| dependency resolution progress was not showing anything | ||
| ([#567](https://github.com/pypa/pip-audit/pull/567)) |
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Needs relocating under [Unreleased] 🙂
woodruffw
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Mar 31, 2023
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| # NOTE(alex): For reasons I'm unsure about, reading the stderr stream in | ||
| # real time seems to interfere with stdout and cause us to read nothing. | ||
| # Let's wait until the process is terminated before reading stderr. | ||
| stderr = process.stderr.read() # type: ignore |
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Hmm, I'm a little worried this might cause deadlocks in some (unlikely) conditions: I can imagine a case where pip writes to stderr before stdout and blocks waiting for the parent's corresponding read, meaning that process.poll() never sees a process termination (and stdout.read(bufsize) always results in an empty read).
Specifically, that should only happen if pip writes enough to stderr to saturate the underlying pipe buffer. But that might happen, so it's probably worth root causing what's going on here instead of deferring the stderr read.
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This code is going to be reworked as part of #574 so let's see if that fixes it. |
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Related to #536. I noticed this when debugging something else. For some reason, when we read
stderrin the polling loop, it causes us to read nothing forstdout. There's no reason that we need to readstderrin the loop since it's not getting dumped into the log window so I just moved this code out of the loop.