Try to trigger android test only if necessary

.github/scripts/check_path_match.py

@@ -0,0 +1,40 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+
+"""
+Helper to determine whether a CI should run on a list of modified files.
+Takes a list of modified files and a list of matchers.
+If any modified file matches to the matcher, print '1' to indicate CI should
+run.
+"""
+
+
+import re
+
+
+def filename_matches(filename: str, matchers: list[str]):
+    combined = "(" + ")|(".join(matchers) + ")"
+    return re.match(combined, filename)
+
+
+def any_match(modified_files: list[str], matchers: list[str]):
+    return any(filename_matches(f, matchers) for f in modified_files)
+
+
+def main(modified_file_list_path: str, matchers_path: str):
+    with open(modified_file_list_path, "r") as f:
+        modified_files = f.read().splitlines()
+    with open(matchers_path, "r") as f:
+        matchers = f.read().splitlines()
+    if any_match(modified_files, matchers):
+        print("1")
+    else:
+        print("0")
+
+
+if __name__ == "__main__":
+    main()

.github/workflows/_android.yml

@@ -5,9 +5,53 @@ on:
   workflow_dispatch:
 
 jobs:
+  check_path:
+    name: Check whether the affected path needs to be validated by this CI
+    runs-on: ubuntu-22.04
+    outputs:
+      should_run: ${{ steps.check-path.outputs.should_run }}
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: '0'
+    - uses: actions/setup-python@v4
+      with:
+        python-version: '3.10'
+    - name: Check path
+      id: check-path
+      env:
+        GITHUB_PR_NUMBER: ${{ github.event.pull_request.number }}
+        GITHUB_PR_BASE: ${{ github.base_ref }}
+        GITHUB_PR_HEAD: ${{ github.head_ref }}
+      run: |
+        if [ -z "$GITHUB_PR_NUMBER" ]; then
+          # It's not for a PR, but pushed to a branch in pull.yml, or dispatch. Always run.
+          echo "::set-output should_run=1"
+          return 0
+        fi
+        if [ -z "$GITHUB_PR_BASE" ] || [ -z "$GITHUB_PR_HEAD" ] ; then
+          # Seems like not a well-formed PR
+          echo "::set-output should_run=1"
+          return 0
+        fi
+        git diff --name-only "$GITHUB_PR_BASE" "$GITHUB_PR_HEAD" > modified_files
+        cat >> matcher<< EOF
+        .ci/docker/
+        .github/workflows/android.yml
+        build/.*android.*.sh
+        install_requirements.sh
+        examples/demo-apps/android
+        extension/android
+        extension/benchmark/android
+        extension/module
+        EOF
+        echo "::set-output should_run=$(python .github/scripts/check_path_match.py modified_files matcher)"
+
   build-llm-demo:
     name: build-llm-demo
     uses: pytorch/test-infra/.github/workflows/linux_job.yml@main
+    needs: check_path
+    if: ${{ needs.check_path.outputs.should_run }} == '1'
     with:
       runner: linux.2xlarge
       docker-image: executorch-ubuntu-22.04-clang12-android