From 800505d98e454a05d8fbf5126eb829bead66d4cf Mon Sep 17 00:00:00 2001
From: Peter Bengtsson <peterbe@github.com>
Date: Tue, 16 Jul 2024 16:29:08 -0400
Subject: [PATCH] Test if repo-sync is necessary (#51270)

---
 .github/workflows/repo-sync.yml          | 59 ++++++++++++++++++++++++
 src/workflows/tests/actions-workflows.js |  4 +-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/repo-sync.yml b/.github/workflows/repo-sync.yml
index d4f549a1f7f1..410ed07a26cc 100644
--- a/.github/workflows/repo-sync.yml
+++ b/.github/workflows/repo-sync.yml
@@ -17,14 +17,73 @@ permissions:
   pull-requests: write
 
 jobs:
+  test-for-equality:
+    if: github.repository == 'github/docs-internal' || github.repository == 'github/docs'
+    name: Test for equality
+    runs-on: ubuntu-latest
+    outputs:
+      is-different: ${{ steps.set-is-different.outputs.result }}
+    steps:
+      - name: Check out docs
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+        with:
+          ref: main
+          repository: github/docs
+          token: ${{ secrets.DOCS_BOT_PAT_WORKFLOW }}
+          path: docs
+      - name: Check out docs-internal
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+        with:
+          ref: main
+          repository: github/docs-internal
+          token: ${{ secrets.DOCS_BOT_PAT_WORKFLOW }}
+          path: docs-internal
+
+      - name: Diff the two repos
+        id: set-is-different
+        run: |
+
+          # Order doesn't matter because we only care if they're different or not
+          # First a test to print the differences, if there is any.
+          # The '|| true' is just to avoid failing the job just because there is a difference.
+          diff -qr -x .git docs docs-internal || true
+
+          # The output means, for example, `true` means there
+          # *are* differences.
+          diff -qr -x .git docs docs-internal && echo "result=false" >> $GITHUB_OUTPUT || echo "result=true" >> $GITHUB_OUTPUT
+
+      # Doesn't matter which repo we use
+      - uses: ./docs-internal/.github/actions/slack-alert
+        if: ${{ failure() && github.event_name != 'workflow_dispatch' }}
+        with:
+          slack_channel_id: ${{ secrets.DOCS_ALERTS_SLACK_CHANNEL_ID }}
+          slack_token: ${{ secrets.SLACK_DOCS_BOT_TOKEN }}
+
   repo-sync:
+    # This is deliberately commented out like this.
+    # The job before this, `test-for-equality`, will set the output which
+    # will conclude if the files in github/docs and github/docs-internal
+    # are NOT identical.
+    # But as as of June 2024, let's be careful and let this logic just
+    # print until we're confident that the comparison is working correctly.
+    # Once we're confident, we can uncomment this.
+    # if: (github.repository == 'github/docs-internal' || github.repository == 'github/docs') && needs.test-for-equality.outputs.is-different == 'true'
     if: github.repository == 'github/docs-internal' || github.repository == 'github/docs'
+    needs: test-for-equality
     name: Repo Sync
     runs-on: ubuntu-latest
     steps:
       - name: Check out repo
         uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
 
+      - name: Test for equality (different)
+        if: ${{ needs.test-for-equality.outputs.is-different == 'true' }}
+        run: echo "github/docs and github/docs-internal are different."
+
+      - name: Test for equality (same)
+        if: ${{ needs.test-for-equality.outputs.is-different == 'false' }}
+        run: echo "You'll find that github/docs and github/docs-internal are identical."
+
       - name: Sync repo to branch
         uses: repo-sync/github-sync@3832fe8e2be32372e1b3970bbae8e7079edeec88
         with:
diff --git a/src/workflows/tests/actions-workflows.js b/src/workflows/tests/actions-workflows.js
index a44c5b5dab55..f67868bd0379 100644
--- a/src/workflows/tests/actions-workflows.js
+++ b/src/workflows/tests/actions-workflows.js
@@ -100,7 +100,9 @@ describe('GitHub Actions workflows', () => {
     'scheduled workflows slack alert on fail $filename',
     ({ filename, data }) => {
       for (const [name, job] of Object.entries(data.jobs)) {
-        if (!job.steps.find((step) => step.uses === './.github/actions/slack-alert')) {
+        if (
+          !job.steps.find((step) => step.uses && step.uses.endsWith('.github/actions/slack-alert'))
+        ) {
           throw new Error(`Job ${filename} # ${name} missing slack alert on fail`)
         }
       }