Add a cron job for testing third-party users of typing_extensions

.github/workflows/ci.yml

@@ -1,6 +1,8 @@
 name: Test and lint
 
 on:
+  schedule:
+    - cron: "0 2 * * *"  # 2am UTC
   push:
     branches:
       - main
@@ -21,6 +23,14 @@ jobs:
   tests:
     name: Run tests
 
+    if: >-
+      # if 'schedule' was the trigger,
+      # don't run it on contributors' forks
+      ${{
+        github.repository == 'python/typing_extensions'
+        || github.event_name != 'schedule'
+      }}
+
     strategy:
       fail-fast: false
       matrix:
@@ -51,6 +61,9 @@ jobs:
   linting:
     name: Lint
 
+    # no reason to run this as a cron job
+    if: github.event_name != 'schedule'
+
     runs-on: ubuntu-latest
 
     steps:
@@ -74,3 +87,32 @@ jobs:
 
       - name: Lint tests
         run: flake8 --config=.flake8-tests src/test_typing_extensions.py --color always
+
+  create-issue-on-failure:
+    name: Create an issue if daily tests failed
+    runs-on: ubuntu-latest
+
+    needs: [tests]
+
+    if: >-
+        ${{
+          github.repository == 'python/typing_extensions'
+          && always()
+          && github.event_name == 'schedule'
+          && needs.tests.result == 'failure'
+        }}
+
+    permissions:
+      issues: write
+
+    steps:
+      - uses: actions/github-script@v6
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            await github.rest.issues.create({
+              owner: "python",
+              repo: "typing_extensions",
+              title: `Daily tests failed on ${new Date().toDateString()}`,
+              body: "Runs listed here: https://github.com/python/typing_extensions/actions/workflows/ci.yml",
+            })