Merge pull request #31599 from Expensify/Rory-FixTypecheck

[No QA] Cross-check the files touched by a PR in typecheck

.github/workflows/typecheck.yml

@@ -24,8 +24,16 @@ jobs:
       - name: Check for new JavaScript files
         run: |
           git fetch origin main --no-tags --depth=1
-          count_new_js=$(git diff --name-only --diff-filter=A origin/main HEAD -- 'src/libs/*.js' 'src/hooks/*.js' 'src/styles/*.js' 'src/languages/*.js' | wc -l)
+
+          # Explanation:
+          #  - comm is used to get the intersection between two bash arrays
+          #    - git diff is used to see the files that were added on this branch
+          #    - gh pr view is used to list files touched by this PR. Git diff may give false positives if the branch isn't up-to-date with main
+          #  - wc counts the words in the result of the intersection
+          count_new_js=$(comm -1 -2 <(git diff --name-only --diff-filter=A origin/main HEAD -- 'src/libs/*.js' 'src/hooks/*.js' 'src/styles/*.js' 'src/languages/*.js') <(gh pr view ${{ github.event.pull_request.number }} --json files | jq -r '.files | map(.path) | .[]') | wc -l)
           if [ "$count_new_js" -gt "0" ]; then
             echo "ERROR: Found new JavaScript files in the /src/libs, /src/hooks, /src/styles, or /src/languages directories; use TypeScript instead."
             exit 1
           fi
+        env:
+          GITHUB_TOKEN: ${{ github.token }}