PERF002 — missing-concurrency-group

Severity: info · Category: Performance · Autofix: yes

What it checks

Flags a workflow triggered by pull_request with no top-level concurrency: block.

Why it matters

Without a concurrency group, pushing a second commit to the same PR doesn't cancel the still-running check from the first push — both keep occupying runners and billed minutes until they finish, even though only the newer one's result will ever matter.

Examples

Flagged:

name: CI
on: pull_request
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - run: npm test

Fixed:

name: CI
on: pull_request
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - run: npm test

Suppressing

This finding is always reported at line 1 of the file (it's a whole-workflow property, not tied to any specific job or step), so the inline comment has to go on the file's very first line:

name: CI # vlotpipe: ignore[PERF002]
on: pull_request

Using .vlotpipe.yml instead is usually cleaner for this one, since "line 1" isn't a natural place to explain the reasoning:

ignore:
  - code: PERF002
    path: ci.yml
    reason: "single short job, cancellation overhead isn't worth it"

Autofix

vlotpipe scan --fix (or check --fix) inserts the exact block shown above (group: ${{ github.workflow }}-${{ github.ref }}, cancel-in-progress: true) immediately before jobs: — the standard form for this pattern, not something specific to your workflow, so review it if a workflow has a reason to keep superseded runs alive.