feat(remap transform): make --watch-config watch external VRL files in remap transforms

[nekorro]

Summary

This change ensures that updates to VRL source code are respected when calculating configuration diffs. External VRL files referenced in remap transforms (via file or files fields) are now tracked when --watch-config is enabled, allowing Vector to reload the configuration automatically when these files change.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Test file field

Added a remap transform to config/vector.yaml :

transforms:
  remap_logs:
    type: remap
    file: vrl/vrl_one
    inputs:
      - demo_logs_one

Started Vector with vector -vvv -c config/vector.yaml -w
Then, modified the /vector/vrl/vrl_one file.
Vector detected the change and reloaded the configuration automatically as expected.

Test files field

Added a remap transform to config/vector.yaml :

transforms:
  remap_logs:
    type: remap
    files:
      - vrl/vrl_one
      - vrl/vrl_two
    inputs:
      - demo_logs_one

Started Vector with vector -vvv -c config/vector.yaml -w
Then, modified the /vector/vrl/vrl_two file.
Vector detected the change and reloaded the configuration automatically as expected.

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Notes

• Please read our Vector contributor resources.
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References

• Ref: #17283
• Closes: #9819

[bits-bot]

All committers have signed the CLA.

[nazarovkv]

Any updates on this PR?

[nekorro]

@pront
Ready for review.

[pront]

@pront Ready for review.

Looks great now. Did you repeat the reload tests with these changes?

[nekorro]

Did you repeat the reload tests with these changes?

Yes, I verified that the transform component reloads correctly when external VRL files specified via file or files (both with absolute and relative paths) are modified.
I’ve also updated the logs in the PR description accordingly.

[pront]

Thank you @nekorro. This was a highly requested enhancement!