fix(controller): skip empty optional step artifacts

[rwong2888]

• Ran make pre-commit -B
• Signed-off commits with Conventional Commit messages
• PR title is a conventional commit message (it becomes the release notes entry)
• Unit or e2e tests cover the change
• For features: an associated issue and a feature description file (make feature-new)
• Opened as draft; will mark "Ready for review" once builds are green

Fixes #16477

Motivation

A running step that consumes an optional: true artifact from a skipped step can retain an empty artifact placeholder. Later PodSpecPatch substitution then attempts to resolve that placeholder and fails.

Modifications

Drop optional step artifact arguments that resolve without an artifact location or key. Add a controller regression test covering an optional artifact resolved from a skipped step output.

Verification

Ran:

KUBECONFIG=/dev/null go test -run 'Test(OptionalArgumentAndParameter|ResolveReferencesSkipsOptionalArtifactFromSkippedStep)' ./workflow/controller/

I also built the controller and argoexec and updated the controller's image and the configmap'as argoexec image.

I reran the workflow in the issue and it passed.

Documentation

No documentation change is needed. This restores the documented behavior of optional artifact inputs.

AI

GitHub Copilot assisted with investigation, implementation, test creation, and this PR description.

Summary by CodeRabbit

• Bug Fixes
  • Optional artifacts without available data are no longer passed to workflow steps.
  • Steps depending on skipped optional artifacts now proceed without invalid artifact arguments.
• Tests
  • Added coverage to verify optional artifacts from skipped steps are correctly omitted.

[github-actions]

✅ PR readiness: all clear

All contributor-fixable checks are passing. A maintainer will take it from here — thanks!

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 39.92%. Comparing base (79ef17f) to head (ff11a6e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16839      +/-   ##
==========================================
- Coverage   39.95%   39.92%   -0.04%     
==========================================
  Files         569      569              
  Lines       44724    44726       +2     
==========================================
- Hits        17869    17855      -14     
- Misses      25074    25086      +12     
- Partials     1781     1785       +4     

Flag	Coverage Δ
unit-tests	39.90% <100.00%> (-0.04%)	⬇️
unit-tests-windows	28.79% <ø> (-0.01%)	⬇️

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 57c43893-8096-4ce2-b2d2-d1426ad7319b

📥 Commits

Reviewing files that changed from the base of the PR and between bde5adf and ff11a6e.

📒 Files selected for processing (2)

• workflow/controller/steps.go
• workflow/controller/steps_test.go

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

resolveReferences now omits optional artifact arguments when resolution produces no location or key. A test covers an optional artifact referencing output from a skipped step.

Changes

Optional artifact resolution

Layer / File(s)	Summary
Skip empty optional artifacts workflow/controller/steps.go, workflow/controller/steps_test.go	resolveReferences omits optional artifacts without a location or key. The test verifies that an artifact from a skipped source step is removed from the step arguments.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to ff11a

The controller now omits empty optional artifact placeholders and includes regression coverage for skipped-step outputs. No actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: joibel, isubasinghe

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main controller change: skipping empty optional step artifacts.
Description check	✅ Passed	The description includes the required checklist, linked issue, motivation, modifications, verification, documentation rationale, and AI disclosure. It provides sufficient detail for review.
Linked Issues check	✅ Passed	The implementation and regression test address issue #16477 by dropping optional artifact arguments that resolve without a location or key when the producing step is skipped.
Out of Scope Changes check	✅ Passed	The changes are limited to the controller behavior and its regression test. They directly support the linked issue and stated objectives.

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