feat(ci): faster breaking change detector

.github/backwards-compatibility-check.sh

@@ -0,0 +1,118 @@
+#!/bin/bash
+# Copyright 2026 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.
+
+set -e
+
+# USAGE:
+#
+#     backwards-compatibility-check.sh COMPONENT [BASE_REF]
+#
+# COMPONENT: The component directory name to run the backwards compatibility check for.
+# BASE_REF: Optional. The baseline git ref (e.g. 'main', 'origin/main' or a release tag) to compare against. Defaults to 'main'.
+
+if [ "$#" -lt 1 ] || [ "$#" -gt 2 ]; then
+    echo "usage: backwards-compatibility-check.sh COMPONENT [BASE_REF]"
+    exit 1
+fi
+
+COMPONENT=$1
+BASE_REF=${2:-main}
+
+# Exception for 'dev'
+if [ "${COMPONENT}" = "dev" ]; then
+    echo "Skipping dev directory (not a public component)."
+    exit 0
+fi
+
+# Check if component directory exists
+if [ ! -d "${COMPONENT}" ]; then
+    echo "Error: Directory ${COMPONENT} does not exist!" >&2
+    exit 1
+fi
+
+# Check if composer.json exists
+COMP_JSON="${COMPONENT}/composer.json"
+if [ ! -f "${COMP_JSON}" ]; then
+    echo "Error: composer.json not found in ${COMPONENT}!" >&2
+    exit 1
+fi
+
+echo "Checking backwards compatibility for component: ${COMPONENT} against baseline: ${BASE_REF}" >&2
+
+# Check if the component existed in the baseline reference
+if ! git rev-parse --verify "${BASE_REF}:${COMPONENT}" >/dev/null 2>&1; then
+    echo "Component ${COMPONENT} did not exist in baseline ${BASE_REF}. Skipping check (all additions)." >&2
+    exit 0
+fi
+
+# Create a temporary directory
+TMP_DIR=$(mktemp -d)
+
+# Initialize a dummy git repo inside TMP_DIR so roave-backward-compatibility-check can compare revisions
+(
+    cd "${TMP_DIR}"
+    git init -q
+)
+
+# Extract baseline files from the BASE_REF, stripping the prefix folder so they land at the root of TMP_DIR
+if ! git archive "${BASE_REF}" "${COMPONENT}" | tar -x --strip-components=1 -C "${TMP_DIR}" 2>/dev/null; then
+    echo "Error: Failed to archive and extract files for ${COMPONENT} from git ref ${BASE_REF}." >&2
+    rm -rf "${TMP_DIR}"
+    exit 1
+fi
+
+(
+    cd "${TMP_DIR}"
+    git add -A
+    git commit -q -m "Base state from ${BASE_REF}"
+)
+
+# Copy the current local component files over the baseline repository,
+# making sure to exclude vendor directories or composer-local files.
+echo "Applying local changes from ${COMPONENT} to the baseline clone..." >&2
+rsync -a --exclude="vendor/" --exclude="composer-local.json" "${COMPONENT}/" "${TMP_DIR}/"
+
+# Commit the changes in the cloned split repository so we can compare them
+CODE=0
+if (
+    cd "${TMP_DIR}"
+    git add -A
+
+    # Check if there are any changes to commit
+    if ! git diff --cached --quiet; then
+        git commit -q -m "Apply local PR changes"
+        echo "Running Roave Backward Compatibility Check..." >&2
+
+        # Locate the roave binary portably
+        COMPOSER_BIN=$(composer global config bin-dir --absolute 2>/dev/null || echo ~/.composer/vendor/bin)
+        ROAVE_BIN=$(command -v roave-backward-compatibility-check || echo "${COMPOSER_BIN}/roave-backward-compatibility-check")
+
+        if ! "${ROAVE_BIN}" --from=HEAD~1 --format=markdown; then
+            echo "❌ BC Breaks detected in ${COMPONENT}!" >&2
+            exit 1
+        else
+            echo "✅ No BC Breaks detected in ${COMPONENT}." >&2
+        fi
+    else
+        echo "No files modified for ${COMPONENT} compared to ${BASE_REF}. Skipping check." >&2
+    fi
+); then
+    CODE=0
+else
+    CODE=1
+fi
+
+rm -rf "${TMP_DIR}"
+exit $CODE

.github/workflows/release-checks.yaml

@@ -5,6 +5,7 @@
     branches: ['main']
 permissions:
   contents: read
+  pull-requests: write
 jobs:
   # More info at https://github.com/Roave/BackwardCompatibilityCheck.
   backwards-compatibility-check:
@@ -12,50 +13,71 @@
     runs-on: ubuntu-latest
     if: ${{ !contains(github.event.pull_request.body, 'BREAKING_CHANGE_REASON=') }}
     steps:
       - uses: actions/checkout@v7
         with:
           fetch-depth: 0
       - name: "Install PHP"
         uses: shivammathur/setup-php@v2
         with:
           php-version: "8.1"
-      - name: "Rebase PR branch onto main branch"
-        if: github.event.pull_request.user.login != 'release-please[bot]'
-        run: |
-          git config user.name "Github Actions"
-          git config user.email "actions@github.com"
-          git checkout ${{ github.event.pull_request.head.sha }}
-          if ! git rebase origin/main; then
-            echo "Failed to rebase PR branch onto main. There may be conflicts. Please resolve conflicts or rebase manually."
-            exit 1
-          fi
       - name: "Install dependencies"
         run: composer global require "roave/backward-compatibility-check:^8.2"
-      - name: "Check for BC breaks"
-        if: github.event.pull_request.user.login != 'release-please[bot]'
-        run: |
-          ~/.composer/vendor/bin/roave-backward-compatibility-check --from=origin/main --format=github-actions
-      - name: "Check for BC label"
-        run: |
-          if [[ "true" == "${{ contains(github.event.pull_request.title, '!:') }}" ]]; then
-            echo "Breaking change label found in PR title"
-            exit 1
-          fi
       - name: Get Latest Release
         if: github.event.pull_request.user.login == 'release-please[bot]'
         id: latest-release
         uses: pozetroninc/github-action-get-latest-release@master
         with:
           repository: ${{ github.repository }}
           token: ${{ secrets.GITHUB_TOKEN }}
-      - name: "Check for BC breaks (Next Release)"
-        if: github.event.pull_request.user.login == 'release-please[bot]'
-        # We've already approved and justified the breaking changes. Run the check but continue on error
-        continue-on-error: true
+      - name: "Check for BC breaks"
+        id: check-bc
+        run: |
+          git config --global user.name "Github Actions"
+          git config --global user.email "actions@github.com"
+          BASE_REF="${{ steps.latest-release.outputs.release }}"
+          BASE_REF=${BASE_REF:-origin/main}
+          CHANGED_COMPONENTS=$(git diff ${BASE_REF} --name-only | grep -E '^[A-Z][a-zA-Z0-9]*/' | cut -d'/' -f1 | sort -u)
+          if [ -z "${CHANGED_COMPONENTS}" ]; then
+            echo "No public component directories have changed. Skipping backwards compatibility checks."
+            exit 0
+          fi
+          BC_BREAKS=""
+          for COMPONENT in ${CHANGED_COMPONENTS}; do
+            BC_BREAKS="$BC_BREAKS$(bash .github/backwards-compatibility-check.sh "${COMPONENT}" "${BASE_REF}")"
+          done
+          # Set GITHUB_OUTPUT
+          printf "bc-breaks<<EOF\n%s\nEOF\n" "$BC_BREAKS" >> $GITHUB_OUTPUT
+      - name: "Prepare BC break report"
+        id: format-comment
+        run: |
+          BC_BREAKS="${{ steps.check-bc.outputs.bc-breaks }}"
+          if [ -n "$BC_BREAKS" ]; then
+            COMMENT_BODY="This PR contains backward compatibility breaking changes detected by the automated BC check against the latest release. Please review the details below:"
+            COMMENT_BODY="$COMMENT_BODY"$'\n\n'"$BC_BREAKS"
+          else
+            COMMENT_BODY="✅ No backwards compatibility breaking changes were detected."
+          fi
+          printf "comment-body<<EOF\n%s\nEOF\n" "$COMMENT_BODY" >> $GITHUB_OUTPUT
+      - name: "Validate standard PR results"
+        if: github.event.pull_request.user.login != 'release-please[bot]'
         run: |
-          ~/.composer/vendor/bin/roave-backward-compatibility-check \
-              --from=${{ steps.latest-release.outputs.release }} \
-              --to=origin/main --format=github-actions
+          if [ -n "${{ steps.check-bc.outputs.bc-breaks }}" ]; then
+            echo "❌ ${{ steps.format-comment.outputs.comment-body }}"
+            exit 1
+          elif [[ "true" == "${{ contains(github.event.pull_request.title, '!:') }}" ]]; then
+            echo "❌ Error: You indicated breaking changes in your PR title (!:), but no backwards compatibility breaks were detected by the automated check."
+            exit 1
+          else
+            echo "✅ No backwards compatibility breaks detected."
+          fi
+      - name: "Add or update PR comment with BC breaks for Release PRs"
+        if: github.event.pull_request.user.login == 'release-please[bot]'
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          header: bc-breaking-changes-comment
+          message: |
+            ## ⚠️ Backwards Compatibility (BC) Breaking Changes Notice
+            ${{ steps.format-comment.outputs.comment-body }}
 
   # Ensure the release PR does not contain an unexpected (e.g. 2.0.0) major version release
   # Add "MAJOR_VERSION_ALLOWED=component1,component2" to the PR description to allow major version
@@ -65,11 +87,11 @@
     runs-on: ubuntu-latest
     if: github.event.pull_request.user.login == 'release-please[bot]'
     steps:
       - uses: actions/checkout@v7
         with:
           fetch-depth: 0
       - name: Parse allowed major versions
         uses: actions-ecosystem/action-regex-match@v2
         id: allowed-major-versions
         with:
           text: ${{ github.event.pull_request.body }}
@@ -78,7 +100,7 @@
       - name: "Check for unexpected major version"
         run: |
           # parse allowed major versions into an array
           IFS=', ' read -r -a ALLOWED_MAJOR_VERSIONS <<< "${{ steps.allowed-major-versions.outputs.group1 }}"
           # get all changed components
           COMPONENTS=$(git diff origin/main --name-only | grep VERSION | xargs dirname)
           FAIL=""
@@ -105,7 +127,7 @@
 
   next-release-label-check:
     name: Check for "next release" label
     uses: GoogleCloudPlatform/php-tools/.github/workflows/release-checks.yml@main
     if: github.event.pull_request.user.login == 'release-please[bot]'
     with:
       next-release-label-check: true
@@ -116,11 +138,11 @@
     runs-on: ubuntu-latest
     if: github.event.pull_request.user.login == 'release-please[bot]'
     steps:
       - uses: actions/checkout@v7
         with:
           fetch-depth: 0
       - name: "Install PHP"
         uses: shivammathur/setup-php@v2
         with:
           php-version: "8.2"
       - name: "Install dependencies"