fix: Use the output_file variable in issue_metrics.py

[jakeatoms]

Pull Request

Proposed Changes

Resolves #479

When the OUTPUT_FILE env variable is specified in a calling Action, it is used everywhere except when checking for file size and splitting into multiple files. The default issue_metrics.md name was hardcoded.

This PR updates the script to use the provided output_file name and uses that naming as the basis for the smaller file names.

Readiness Checklist

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[jmeridth]

@jakeatoms great addition. Thank you. Could you please alter or add some new tests to ensure this doesn't regress?

[jakeatoms]

@jakeatoms great addition. Thank you. Could you please alter or add some new tests to ensure this doesn't regress?

Will do!

[jakeatoms]

@jakeatoms great addition. Thank you. Could you please alter or add some new tests to ensure this doesn't regress?

@jmeridth OK, to accomplish testing without strictly testing main, I extracted the code that works with the output file to a separate function and tested that directly. We're now testing interaction with the various function calls and covering True and False scenarios. It's still not strictly testing that main isn't passing a hardcoded value, but to test that would involve a huge amount of mocking.

Let me know if you think this is sufficient, thanks!

[zkoppert]

Awesome! Thanks for the fix!

[damian131]

I think there may be an issue introduced by these changes which leads to not taking a default value of OUTPUT_FILE. In case it's not specified explicitly, it fails with:

Traceback (most recent call last):
  File "/action/workspace/issue_metrics.py", line 3[76](https://github.com/***/actions/runs/13810828313/job/38631843761#step:4:77), in <module>
    main()
    ~~~~^^
  File "/action/workspace/issue_metrics.py", line 372, in main
    evaluate_markdown_file_size(output_file)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/action/workspace/issue_metrics.py", line 176, in evaluate_markdown_file_size
    if markdown_too_large_for_issue_body(output_file, max_char_count):
       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/action/workspace/markdown_helpers.py", line 16, in markdown_too_large_for_issue_body
    with open(file_path, "r", encoding="utf-8") as file:
         ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: ''

[moritzschmitz-oviva]

@damian131 This should be resolved with https://github.com/github/issue-metrics/releases/tag/v3.18.3. Can you confirm?