shaheeramjad opened a new pull request, #37536:
URL: https://github.com/apache/beam/pull/37536
### Problem
When a pip subprocess fails and the command is passed as a short list (e.g.
`['python', '-m', 'pip', 'install', 'pkg']`), the exception handler in
`sdks/python/apache_beam/utils/processes.py` raised **IndexError** instead of
the intended RuntimeError with traceback and pip output.
The pip-specific branch used a hardcoded index 6 for the "package name" when
formatting the error message (`.format(..., args[0][6], ...)`). For `pip
install <pkg>` the command list has only 5 elements (indices 0–4), so
`args[0][6]` caused **IndexError** and users saw a crash instead of a clear
error message.
### Solution
- **Added `_pip_package_from_args(args)`**
Returns a safe string for the "package" field: uses `args[0][6]` only when
`args` is a tuple, `args[0]` is a list/tuple, and `len(args[0]) > 6`; otherwise
returns `"see output below"`.
- **Guarded the pip branch**
Replaced `(args[0][2] == "pip")` with `len(args[0]) > 2 and args[0][2] ==
"pip"` so we never index `args[0][2]` on a short list.
- **Updated `call`, `check_call`, and `check_output`**
All three now use `_pip_package_from_args(args)` instead of `args[0][6]`
when building the pip error message.
### Files changed
- **`sdks/python/apache_beam/utils/processes.py`**
- New helper `_pip_package_from_args(args)` (with docstring).
- Pip branch in `call`, `check_call`, and `check_output`: length check +
use of helper for package string.
- **`sdks/python/apache_beam/utils/processes_test.py`**
-
`TestErrorHandlingCheckCall.test_check_call_pip_short_command_no_index_error`
-
`TestErrorHandlingCheckOutput.test_check_output_pip_short_command_no_index_error`
- `TestErrorHandlingCall.test_call_pip_short_command_no_index_error`
Each test uses a short pip command (`['python', '-m', 'pip', 'install',
'nonexistent-package-xyz']`), triggers `CalledProcessError`, and asserts that a
**RuntimeError** is raised (not IndexError) and that the message contains the
subprocess output and `"see output below"`.
### Testing
- All **12** tests in `apache_beam.utils.processes_test` pass, including the
3 new tests and the existing ones (e.g. long pip command with package at index
6).
- Run: `python -m unittest apache_beam.utils.processes_test -v`
### Backward compatibility
- Behavior is unchanged for commands with 7+ elements (e.g. existing `pip
download --dest /var <pkg> ...` still shows the package name at index 6).
- Only the previously broken case (short command) is fixed; no API or
contract changes.
## Related
- Fixes: `Fixes #37515`
- Component: Python SDK
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