Improve the error message when bundled pip cannot be found #1720
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Malax
approved these changes
Dec 12, 2024
The Python stdlib bundles a copy of pip, which the buildpack uses to
bootstrap the real pip installation. This copy of pip should always
exist, and thus not finding it is treated as an internal error.
However, via Honeycomb I discovered one app that manages to hit this
case regardless, and when it does so, the error message is not the
"internal error" error message, but instead a Bash unbound variable
error like:
```
-----> Using Python 3.9.20 specified in .python-version
-----> Using cached install of Python 3.9.20
/tmp/buildpack/lib/utils.sh: line 33: bundled_pip_wheel_list[0]: unbound variable
```
I believe the reason for pip not being found in this case is that the
app source has a broken/EOL Python install committed to it (which
doesn't include the `ensurepip` module), which tricks the cache
restoration into thinking it can re-use the cache.
I will be adding an explicit warning/error for finding an existing
`.heroku/python/` directory in the app in a later PR, however, for now
this change:
(a) fixes the display of the internal error message,
(b) adds more debugging output to the error message so that I can
confirm my theory as to the root cause for this app.
Towards #1710.
GUS-W-17386432.
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The Python stdlib bundles a copy of pip, which the buildpack uses to bootstrap the real pip installation. This copy of pip should always exist, and thus not finding it is treated as an internal error.
However, via Honeycomb I discovered one app that manages to hit this case regardless, and when it does so, the error message is not the "internal error" error message, but instead a Bash unbound variable error like:
My guess for why pip is not being found in this case is that the app's Git repo may have a broken/EOL Python install committed to it (which doesn't include the
ensurepipmodule), which tricks the cache restoration into thinking it can re-use the cache.I will be adding an explicit warning/error for finding an existing
.heroku/python/directory in the app in a later PR, however, for now this change:(a) fixes the display of the internal error message,
(b) adds more debugging output to the error message so that I can confirm my theory as to the root cause for this app.
Towards #1710.
GUS-W-17386432.