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

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References

• Ref: #17283
• Closes: #9819

[bits-bot]

All committers have signed the CLA.

[pront]

If I am reading this changes correctly, we don't need vrl_hash at all. We certainly don't want it as a public config field. This will make a lot of boilerplate code redundant.

[nekorro]

Thanks for the feedback.
You're right, I missed that ComponentConfig is used to match external file paths to component identifiers when reload happens. And it's possible to just pass the list of components to reload into ConfigDiff::new via the components_to_reload parameter. That makes vrl_hash unnecessary.
I also noticed the current implementation doesn't handle relative paths correctly.
I'll update this PR to remove vrl_hash and the related boilerplate, and fix the path comparison logic to support relative paths from the config.

[pront]

Awesome 👍