Add reusable workflow for checking changed file paths

Author: DanielCliftonGuardian

.github/workflows/check-chromatic-paths.yml

@@ -0,0 +1,37 @@
+# Determines whether changed files are relevant to Chromatic.
+# Both dcr-chromatic.yml and chromatic-label-helper.yml call this so the filter
+# list stays in one place and can't drift between the two workflows.
+
+name: Check Chromatic paths
+
+on:
+  workflow_call:
+    outputs:
+      relevant:
+        description: "'true' if any files relevant to visual rendering have changed"
+        value: ${{ jobs.filter.outputs.relevant }}
+
+jobs:
+  filter:
+    name: Check changed paths
+    runs-on: ubuntu-latest
+    outputs:
+      relevant: ${{ steps.filter.outputs.relevant }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+      - uses: dorny/paths-filter@v4
+        id: filter
+        with:
+          # Only run Chromatic if files that affect visual rendering have changed.
+          # Everything not listed here (docs, scripts, config, tests, etc.) is ignored.
+          filters: |
+            relevant:
+              - 'dotcom-rendering/src/**'
+              - 'dotcom-rendering/stories/**'
+              - 'dotcom-rendering/.storybook/**'
+              - 'dotcom-rendering/fixtures/**'
+              - 'dotcom-rendering/package.json'
+              - 'libs/**'
+              - 'pnpm-lock.yaml'

.github/workflows/chromatic-label-helper.yml

@@ -8,30 +8,20 @@ name: Chromatic Label Helper
 on:
   pull_request:
     types: [opened, ready_for_review]
-    paths-ignore:
-      - 'ab-testing/**'
-      - 'scripts/**'
-      - 'dotcom-rendering/cdk/**'
-      - 'dotcom-rendering/cypress/**'
-      - 'dotcom-rendering/docs/**'
-      - 'dotcom-rendering/logs/**'
-      - 'dotcom-rendering/playwright/**'
-      - 'dotcom-rendering/playwright-report/**'
-      - 'dotcom-rendering/scripts/**'
-      - 'dotcom-rendering/test-results/**'
-      - 'dotcom-rendering/__mocks__/**'
-      - '**.md'
-      - '**.yml'
-      - '**/*.d.ts'
 
 jobs:
+  check-paths:
+    name: Check changed paths
+    uses: ./.github/workflows/check-chromatic-paths.yml
+
   write_comment:
     runs-on: ubuntu-latest
+    needs: check-paths
     permissions:
       pull-requests: write
 
-    # We only comment on pull requests that have been marked as ready for review
-    if: ${{ github.event.pull_request.draft == false}}
+    # Only comment when the PR touches files relevant to Chromatic and isn't a draft
+    if: ${{ github.event.pull_request.draft == false && needs.check-paths.outputs.relevant == 'true' }}
 
     steps:
       - uses: actions/github-script@v8

.github/workflows/dcr-chromatic.yml

@@ -9,27 +9,7 @@ on:
 jobs:
   check-paths:
     name: Check changed paths
-    runs-on: ubuntu-latest
-    outputs:
-      relevant: ${{ steps.filter.outputs.relevant }}
-    steps:
-      - uses: actions/checkout@v6
-        with:
-          fetch-depth: 0
-      - uses: dorny/paths-filter@v4
-        id: filter
-        with:
-          # Only run Chromatic if files that affect visual rendering have changed.
-          # Everything not listed here (docs, scripts, config, tests, etc.) is ignored.
-          filters: |
-            relevant:
-              - 'dotcom-rendering/src/**'
-              - 'dotcom-rendering/stories/**'
-              - 'dotcom-rendering/.storybook/**'
-              - 'dotcom-rendering/fixtures/**'
-              - 'dotcom-rendering/package.json'
-              - 'libs/**'
-              - 'pnpm-lock.yaml'
+    uses: ./.github/workflows/check-chromatic-paths.yml
 
   chromatic:
     name: Chromatic