Fix pip-compile to update all lockfiles from single input file

[Copilot]

What are you trying to accomplish?

Fixes #[linked issue] where a single .in file generating multiple .txt lockfiles (e.g., requirements.txt for Python 3.8 and requirements-3.12.txt for Python 3.12) only has one lockfile updated.

Root cause: compiled_file_for_filename used find returning only the first matching file instead of all files referencing the input.

Changes:

• Added compiled_files_for_filename method returning all .txt files with --output-file headers referencing a given .in file
• Modified compile_file to accept explicit output file parameter
• Updated compilation loop to iterate over all output files per input file
• Applied same fix to pip_compile_version_resolver.rb for consistency

Anything you want to highlight for special attention from reviewers?

The fix maintains backward compatibility:

• compiled_file_for_filename (singular) still exists, delegating to .first on the new method
• When no output files are found, falls back to convention-based matching (input.in → input.txt)
• Empty output file list compiles with nil to preserve default pip-compile behavior

How will you know you've accomplished your goal?

Added test case "with multiple output files from a single input file" that:

• Creates two .txt fixtures with different --output-file headers referencing the same .in file
• Verifies both files are updated with the new dependency version

All 27 existing pip_compile_file_updater tests pass.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Only a subset of lockfiles being updated</issue_title>
<issue_description>### Is there an existing issue for this?

• I have searched the existing issues

Package ecosystem

pip-compile

Package manager version

pip-compile 7.4.1

Language version

Python 3.8

Manifest location and content before the Dependabot update

https://github.com/ska-sa/spead2/blob/14739439cd000ca7d83085d6073ad62968e2576e/requirements.in
https://github.com/ska-sa/spead2/blob/14739439cd000ca7d83085d6073ad62968e2576e/requirements.txt
https://github.com/ska-sa/spead2/blob/14739439cd000ca7d83085d6073ad62968e2576e/requirements-3.12.txt

dependabot.yml content

version: 2
updates:
  - package-ecosystem: "github-actions"
    directory: "/"
    schedule:
      interval: "weekly"
  - package-ecosystem: "pip"
    directory: "/"
    schedule:
      interval: "weekly"
    groups:
      production-group:
        dependency-type: "production"
      development-group:
        dependency-type: "development"

Updated dependency

No response

What you expected to see, versus what you actually saw

I have a single source requirements.in, from which I generate two lockfiles: requirements.txt for Python 3.8, and requirements-3.12 for Python 3.12. When Dependabot opens a PR such as ska-sa/spead2#324, it's only updating the latter.

I expected to see updates to requirements.txt as well (whether in the same or a separate PR).

Native package manager behavior

Running pip-compile -U requirements.in in a Python 3.8 environment produces the following diff:

diff --git a/requirements.txt b/requirements.txt
index 6f21686..6bd0eee 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -21,11 +21,11 @@ numpy==1.24.4
     #   -r requirements.in
     #   numba
     #   scipy
-packaging==24.0
+packaging==24.1
     # via pytest
 pluggy==1.5.0
     # via pytest
-pytest==8.2.1
+pytest==8.2.2
     # via
     #   -r requirements.in
     #   pytest-asyncio
@@ -41,5 +41,5 @@ scipy==1.10.1
     # via -r requirements.in
 tomli==2.0.1
     # via pytest
-zipp==3.19.0
+zipp==3.19.2
     # via importlib-metadata

Images of the diff or a link to the PR, issue, or logs

ska-sa/spead2#324

Smallest manifest that reproduces the issue

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Only a subset of lockfiles being updated #9963

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[kbukum1]

LGTM.