chore: add GitHub Action to check imports' order

PiperOrigin-RevId: 766804783

.github/workflows/isort.yml

@@ -0,0 +1,69 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Check sorting of imports
+
+on:
+  pull_request:
+    paths:
+      - '**.py'
+      - 'pyproject.toml'
+
+jobs:
+  isort-check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 2
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.x'
+
+      - name: Install isort
+        run: |
+          pip install isort
+
+      - name: Run isort on changed files
+        id: run_isort
+        run: |
+          git fetch origin ${{ github.base_ref }}
+          CHANGED_FILES=$(git diff --diff-filter=ACMR --name-only origin/${{ github.base_ref }}...HEAD | grep -E '\.py$' || true)
+          if [ -n "$CHANGED_FILES" ]; then
+            echo "Changed Python files:"
+            echo "$CHANGED_FILES"
+            echo ""
+            FORMATTED_FILES=$(echo "$CHANGED_FILES" | tr '\n' ' ')
+
+            # Run isort --check
+            set +e
+            isort --check $CHANGED_FILES
+            RESULT=$?
+            set -e
+            if [ $RESULT -ne 0 ]; then
+              echo ""
+              echo "❌ isort check failed!"
+              echo "👉 To fix import order, run locally:"
+              echo ""
+              echo "    isort $FORMATTED_FILES"
+              echo ""
+              exit $RESULT
+            fi
+          else
+            echo "No Python files changed. Skipping isort check."
+          fi