Exclude fn-config from function input items in kpt fn eval

[aravindtga]

Description

• What changed: When --fn-config points to a file inside the package, the fn-config resource is now excluded from the function's input items in kpt fn eval. The file is preserved unmodified on disk.
• Why it's needed: The fn-config was being passed to the function both as resourceList.functionConfig and as one of resourceList.items, causing functions like create-setters and set-namespace to modify their own configuration file.
• How it works: Before passing resources to the function pipeline, the fn-config is identified by matching its path annotation against FnConfigPath and removed from inputResources. It is added back unmodified to outputResources before writing so the file is not deleted from disk.

Related Issue(s)

• Fixes create-setters adds incorrect comments #2199

Type of Change

• Bug fix
• Tests

Checklist

• Code follows project style guidelines
• Self-reviewed changes
• Tests added/updated
• Documentation added/updated
• All tests and gating checks pass

AI Disclosure

• I have used AI in the creation of this PR.

If so, please describe how:
- Kiro to analyse the issue, implement the fix, and generate unit tests.

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[Copilot]

Pull request overview

This PR fixes kpt fn eval behavior when --fn-config points to a file inside the package, ensuring the fn-config resource is not included in resourceList.items (so functions don’t accidentally mutate their own configuration) while still preserving the file on disk.

Changes:

• Excludes the fn-config resource from function input items when it resides inside the package, and re-adds it to outputs so it isn’t deleted.
• Adds a unit test covering fn-config exclusion behavior.
• Updates e2e expected outputs and CLI documentation to reflect the new semantics.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
thirdparty/kyaml/runfn/runfn.go	Filters fn-config out of function input items and ensures it is written back unmodified.
thirdparty/kyaml/runfn/runfn_test.go	Adds a unit test for fn-config exclusion/preservation behavior.
e2e/testdata/fn-eval/save-fn/custom-pkg-path/.expected/diff.patch	Updates expected patch output so fn-config is no longer modified.
e2e/testdata/fn-eval/save-fn/custom-pkg-path/.expected/config.yaml	Updates expected results summary counts after fn-config exclusion.
documentation/content/en/reference/cli/fn/eval/_index.md	Documents that fn-config is not treated as an input resource and won’t be modified.

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[efiacor]

Just wondering if this is the intended behaviour. Not sure myself