feat(generator): automate compute discovery document updates

.github/workflows/update-compute-discovery.yml

@@ -0,0 +1,62 @@
+name: Update Compute Discovery Document
+
+on:
+  schedule:
+    # Runs every Monday at 09:00 UTC
+    - cron: '0 9 * * 1'
+  workflow_dispatch: # Allows manual trigger from the GitHub Actions UI
+
+permissions:
+  contents: read
+
+jobs:
+  update-compute-discovery:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+
+      - name: Setup Git user identity
+        run: |
+          git config user.name "cloud-cpp-automation[bot]"
+          git config user.email "cloud-cpp-automation[bot]@users.noreply.github.com"
+
+      - name: Run update_discovery_doc.sh
+        run: |
+          ./generator/discovery/update_discovery_doc.sh --no-create-branch
+
+      - name: Run checkers
+        run: |
+          ci/cloudbuild/build.sh -t checkers-pr
+
+      - name: Push branch and create Pull Request if changes exist
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # Check if a new commit was made (HEAD differs from origin/main)
+          if [[ "$(git rev-parse HEAD)" != "$(git rev-parse origin/main)" ]]; then
+            echo "Changes detected. Pushing branch automation/update-compute-discovery..."
+            git push origin HEAD:automation/update-compute-discovery --force
+
+            echo "Checking if a PR is already open..."
+            if ! gh pr list --head "automation/update-compute-discovery" --json number -q '.[0].number' | grep -q '^[0-9]'; then
+              echo "Opening new PR..."
+              BODY="Automated update of Compute Engine Discovery Document and generated C++ client code.\n\nTriggered automatically by the \`update-compute-discovery\` workflow."
+              gh pr create \
+                --title "feat(compute): update discovery doc and generate new services" \
+                --body "$(printf '%b' "$BODY")" \
+                --base main \
+                --head automation/update-compute-discovery \
+                --label "autorelease: pending"
+            else
+              echo "Pull request already exists for automation/update-compute-discovery. Branch has been updated."
+            fi
+          else
+            echo "No changes committed. Nothing to push or create."
+          fi

generator/discovery/update_discovery_doc.sh

@@ -86,11 +86,36 @@ readonly GENERATOR_CONFIG_RELATIVE_PATH="generator/generator_config.textproto"
 readonly COMPUTE_SERVICE_DIRS_CMAKE_RELATIVE_PATH="google/cloud/compute/service_dirs.cmake"
 readonly COMPUTE_SERVICE_DIRS_BZL_RELATIVE_PATH="google/cloud/compute/service_dirs.bzl"
 
+CURRENT_REVISION=$(sed -En 's/  \"revision\": \"([[:digit:]]+)\",/\1/p' "${PROJECT_ROOT}/${COMPUTE_DISCOVERY_JSON_RELATIVE_PATH}" 2>/dev/null || echo "")
+
 io::log_h2 "Fetching discovery document from ${COMPUTE_DISCOVERY_DOCUMENT_URL}"
-curl "${COMPUTE_DISCOVERY_DOCUMENT_URL}" >"${PROJECT_ROOT}/${COMPUTE_DISCOVERY_JSON_RELATIVE_PATH}"
+TEMP_JSON=$(mktemp)
+if [[ ! -f "${TEMP_JSON}" ]]; then
+  io::log_red "Failed to create temporary file."
+  exit 1
+fi
+trap 'rm -f "${TEMP_JSON}"' EXIT
 
-REVISION=$(sed -En 's/  \"revision\": \"([[:digit:]]+)\",/\1/p' "${PROJECT_ROOT}/${COMPUTE_DISCOVERY_JSON_RELATIVE_PATH}")
+if ! curl -fsSL "${COMPUTE_DISCOVERY_DOCUMENT_URL}" >"${TEMP_JSON}"; then
+  io::log_red "Failed to fetch discovery document from ${COMPUTE_DISCOVERY_DOCUMENT_URL}"
+  exit 1
+fi
+
+REVISION=$(sed -En 's/  \"revision\": \"([[:digit:]]+)\",/\1/p' "${TEMP_JSON}")
+if [[ -z "${REVISION}" ]]; then
+  io::log_red "Could not parse revision from fetched discovery document."
+  exit 1
+fi
 readonly REVISION
+
+if [[ -n "${CURRENT_REVISION}" && "${REVISION}" == "${CURRENT_REVISION}" ]]; then
+  io::log_green "Compute discovery document is already up to date (revision ${CURRENT_REVISION}). Nothing to do."
+  exit 0
+fi
+
+io::log_h2 "Updating Discovery Document: ${CURRENT_REVISION:-none} -> ${REVISION}"
+mv "${TEMP_JSON}" "${PROJECT_ROOT}/${COMPUTE_DISCOVERY_JSON_RELATIVE_PATH}"
+
 if [[ "${CREATE_BRANCH}" == "true" ]]; then
   io::run git checkout -B update_compute_discovery_circa_"${REVISION}"
 fi