fix(ci): restore per-commit CI runs on main

[CatherineSue]

Description

Problem

#1530 rewrote the concurrency block in pr-test-rust.yml and pr-test-mlx.yml and, alongside the new PR-number-based group key, dropped the event_name == 'pull_request' guard on cancel-in-progress, making it unconditionally true.

For push-to-main, the group key resolves to gateway-tests-main / mlx-tests-main — every commit on main shares one group. With cancel-in-progress: true, when commit B lands while commit A's CI is still running, B joins A's group and kills A's run mid-flight.

This breaks smg's invariant that every commit on main runs CI to completion. Without per-commit CI, a git bisect against a regression on main can land on a commit whose CI was cancelled and therefore has no signal.

The PR-number-based group key for PR events and the new cancel-merged-pr-tests.yml workflow added by #1530 are unaffected by this fix — they only target PR runs.

Solution

Restore the event_name == 'pull_request' guard on cancel-in-progress, keeping the PR-number-based group key from #1530:

concurrency:
  group: gateway-tests-${{ github.event_name == 'pull_request' && format('pr-{0}', github.event.pull_request.number) || github.ref_name }}
  cancel-in-progress: ${{ github.event_name == 'pull_request' }}

Net behavior after this PR:

• PR runs — still cancelled on new pushes within the same PR (preserves the intent of ci: cancel stale PR test runs #1530).
• Main push runs — each commit's CI run completes independently (preserves the per-commit bisection invariant).
• workflow_dispatch on main — shares the main push group; neither cancels the other.

Changes

• .github/workflows/pr-test-rust.yml — change cancel-in-progress: true back to cancel-in-progress: ${{ github.event_name == 'pull_request' }}.
• .github/workflows/pr-test-mlx.yml — same change.

Test Plan

Local checks:

pre-commit run --files .github/workflows/pr-test-rust.yml .github/workflows/pr-test-mlx.yml
git diff --cached --check

Both pass; YAML parses, no whitespace issues.

No Rust or Python sources are touched in this PR, so cargo fmt / cargo clippy are not applicable.

Behavioral verification once merged (observable on main):

• Land a no-op commit on main while the prior commit's PR Test (SMG) is in progress; the prior run should continue to completion (after this PR) instead of being cancelled (before this PR).
• On an open PR, push two consecutive commits — the older run should still be cancelled when the newer one starts (intent of ci: cancel stale PR test runs #1530 preserved).

Checklist

• cargo +nightly fmt passes
• cargo clippy --all-targets --all-features -- -D warnings passes
• (Optional) Documentation updated
• (Optional) Please join us on Slack #sig-smg to discuss, review, and merge PRs

Summary by CodeRabbit

• Chores
  • Optimized GitHub Actions workflow concurrency settings to improve CI/CD efficiency for pull requests.

[gemini-code-assist]

Note

Gemini is unable to generate a review for this pull request due to the file types involved not being currently supported.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 8baa30bd-1a49-4afd-87cd-68e926f20755

📥 Commits

Reviewing files that changed from the base of the PR and between 9341651 and c40bfc9.

📒 Files selected for processing (2)

• .github/workflows/pr-test-mlx.yml
• .github/workflows/pr-test-rust.yml

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📝 Walkthrough

Walkthrough

This PR updates two GitHub Actions test workflows to conditionally cancel in-progress runs only for pull request events. The cancel-in-progress setting in .github/workflows/pr-test-mlx.yml and .github/workflows/pr-test-rust.yml now uses an event-type expression instead of always being true.

Changes

Workflow concurrency settings

Layer / File(s)	Summary
Conditional cancellation in PR test workflows .github/workflows/pr-test-mlx.yml, .github/workflows/pr-test-rust.yml	concurrency.cancel-in-progress is changed from unconditional true to ${{ github.event_name == 'pull_request' }}, allowing in-progress runs to continue when triggered by non-pull-request events.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• lightseekorg/smg#1530: Both PRs modify the same GitHub Actions workflow concurrency settings in pr-test-mlx.yml and pr-test-rust.yml (notably concurrency.group and cancel-in-progress behavior), so the changes overlap at the workflow level.
• lightseekorg/smg#1175: The main PR's change to make cancel-in-progress conditional for pull_request events directly overlaps with the retrieved PR's corresponding update in .github/workflows/pr-test-rust.yml (and related workflow gating changes), so they are code-level related.
• lightseekorg/smg#678: Both PRs modify the GitHub Actions workflow concurrency behavior in .github/workflows/pr-test-rust.yml, changing concurrency.cancel-in-progress to be conditional on pull_request events (${{ github.event_name == 'pull_request' }}) rather than always true.

Suggested labels

ci

Suggested reviewers

• key4ng
• slin1237
• XinyueZhang369

Poem

🐰 Workflows once wild, now gently refined,
Pull requests alone shall keep in-progress confined,
Other events flow free, no cancellation bound,
Efficiency whispers—listen to the sound! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: restoring per-commit CI runs on main by fixing the concurrency configuration in CI workflows.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch catherinesue/restore-main-per-commit-ci

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[claude]

Looks good. The cancel-in-progress change correctly preserves per-commit CI on main while still cancelling superseded PR runs. Clean and consistent across both workflow files.