🏗 Clean up CircleCI merge SHA logic

.circleci/compute_merge_commit.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+#
+# Copyright 2021 The AMP HTML Authors. All Rights Reserved.
+#
+# 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.
+
+# This script establishes the merge commit at the start of a CircleCI build so
+# all stages use the same commit.
+
+set -e
+err=0
+
+GREEN() { echo -e "\n\033[0;32m$1\033[0m"; }
+
+# Try to determine the PR number.
+curl -sS https://raw.githubusercontent.com/ampproject/amphtml/master/.circleci/get_pr_number.sh | bash
+source $BASH_ENV
+
+# If PR_NUMBER doesn't exist, there is nothing more to do.
+if [[ -z "$PR_NUMBER" ]]; then
+  exit 0
+fi
+
+# GitHub provides refs/pull/<PR_NUMBER>/merge, an up-to-date merge branch for
+# every PR branch that can be cleanly merged to master. For more details, see:
+# https://discuss.circleci.com/t/show-test-results-for-prospective-merge-of-a-github-pr/1662
+MERGE_BRANCH="refs/pull/$PR_NUMBER/merge"
+echo $(GREEN "Computing merge SHA of $MERGE_BRANCH...")
+CIRCLE_MERGE_SHA="$(git ls-remote https://github.com/ampproject/amphtml.git "$MERGE_BRANCH" | awk '{print $1}')"
+
+echo "$CIRCLE_MERGE_SHA" > .CIRCLECI_MERGE_COMMIT
+echo $(GREEN "Stored merge SHA $CIRCLE_MERGE_SHA in .CIRCLECI_MERGE_COMMIT.")
+exit 0

.circleci/config.yml

@@ -17,6 +17,10 @@ push_builds_only: &push_builds_only
         - /^amp-release-.*$/
 
 executors:
+  amphtml-docker-small-executor:
+    docker:
+      - image: cimg/base:2020.12
+    resource_class: small
   amphtml-medium-executor:
     machine:
       image: ubuntu-2004:202010-01
@@ -29,11 +33,6 @@ executors:
     machine:
       image: ubuntu-2004:202010-01
     resource_class: xlarge
-  amphtml-docker-executor:
-    docker:
-      # The official, bare bones Docker Image from CircleCI
-      # https://circleci.com/docs/2.0/circleci-images/?section=executors-and-images#circleci-base-image
-      - image: cimg/base:2020.12
 
 commands:
   save_merge_commit:
@@ -42,7 +41,7 @@ commands:
           name: 'Save Merge Commit'
           key: git-{{ .Branch }}-{{ .Revision }}
           paths:
-            - .CIRCLECI_WORKFLOW_MERGE_COMMIT
+            - .CIRCLECI_MERGE_COMMIT
   restore_merge_commit:
     steps:
       - restore_cache:
@@ -54,7 +53,7 @@ commands:
       - restore_merge_commit
       - run:
           name: 'Fetch Merge Commit'
-          command: ./.circleci/fetch_merge_commit.sh merge
+          command: ./.circleci/fetch_merge_commit.sh
       - run:
           name: 'Check Config'
           command: ./.circleci/check_config.sh
@@ -81,11 +80,11 @@ commands:
 jobs:
   'Compute Merge Commit':
     executor:
-      name: amphtml-docker-executor
+      name: amphtml-docker-small-executor
     steps:
       - run:
-          name: 'Fetch Merge Commit'
-          command: curl -o- https://raw.githubusercontent.com/ampproject/amphtml/master/.circleci/fetch_merge_commit.sh | bash /dev/stdin fetch
+          name: 'Compute Merge Commit'
+          command: curl -sS https://raw.githubusercontent.com/ampproject/amphtml/master/.circleci/compute_merge_commit.sh | bash
       - save_merge_commit
   'Checks':
     executor:

.circleci/fetch_merge_commit.sh

@@ -16,64 +16,29 @@
 
 # This script fetches the merge commit of a PR branch with master to make sure
 # PRs are tested against all the latest changes on CircleCI.
-# Reference: https://circleci.com/docs/2.0/env-vars/#built-in-environment-variables
 
 set -e
 err=0
 
 GREEN() { echo -e "\n\033[0;32m$1\033[0m"; }
-YELLOW() { echo -e "\n\033[0;33m$1\033[0m"; }
 RED() { echo -e "\n\033[0;31m$1\033[0m"; }
 
-if [[ -z "$1" ]]; then
-  echo "Usage: fetch_merge_commit.sh [fetch | merge]"
-  exit 1
-fi
+# Try to determine the PR number.
+./.circleci/get_pr_number.sh
+source $BASH_ENV
 
-# Push builds are only run against master and amp-release branches.
-if [[ "$CIRCLE_BRANCH" == "master" || "$CIRCLE_BRANCH" =~ ^amp-release-* ]]; then
-  echo $(GREEN "Nothing to do because $CIRCLE_BRANCH is not a PR branch.")
-  # Warn if the build is linked to a PR on a different repo (known CircleCI bug).
-  if [[ -n "$CIRCLE_PULL_REQUEST" && ! "$CIRCLE_PULL_REQUEST" =~ ^https://github.com/ampproject/amphtml* ]]; then
-    echo $(YELLOW "WARNING: Build is incorrectly linked to a PR outside ampproject/amphtml:")
-    echo $(YELLOW "$CIRCLE_PULL_REQUEST")
-  fi
-  exit 0
-fi
-
-# CIRCLE_PR_NUMBER is present for PRs originating from forks, but absent for PRs
-# originating from a branch on the main repo. In such cases, extract the PR
-# number from CIRCLE_PULL_REQUEST.
-if [[ "$CIRCLE_PR_NUMBER" ]]; then
-  PR_NUMBER=$CIRCLE_PR_NUMBER
-else
-  PR_NUMBER=${CIRCLE_PULL_REQUEST#"https://github.com/ampproject/amphtml/pull/"}
-fi
-
-# If neither CIRCLE_PR_NUMBER nor CIRCLE_PULL_REQUEST are available, it's
-# possible this is a PR branch that is yet to be associated with a PR. Exit
-# early becaue there is no merge commit to fetch.
+# If PR_NUMBER doesn't exist, there is nothing more to do.
 if [[ -z "$PR_NUMBER" ]]; then
-  echo $(GREEN "Nothing to do because $CIRCLE_BRANCH is not yet linked to a PR.")
   exit 0
 fi
 
-if [[ "$1" == "fetch" ]]; then
-  # GitHub provides refs/pull/<PR_NUMBER>/merge, an up-to-date merge branch for
-  # every PR branch that can be cleanly merged to master. For more details, see:
-  # https://discuss.circleci.com/t/show-test-results-for-prospective-merge-of-a-github-pr/1662
-  MERGE_BRANCH="refs/pull/$PR_NUMBER/merge"
-  echo $(GREEN "Fetching merge SHA from $MERGE_BRANCH...")
-
-  CIRCLE_MERGE_SHA="$(git ls-remote https://github.com/ampproject/amphtml.git "$MERGE_BRANCH" | awk '{print $1}')"
-  echo $(GREEN "Fetched merge SHA $CIRCLE_MERGE_SHA...")
-  echo "$CIRCLE_MERGE_SHA" > .CIRCLECI_WORKFLOW_MERGE_COMMIT
-  exit 0
-fi
+# Extract the merge commit for this workflow and make it visible to other steps.
+CIRCLECI_MERGE_COMMIT="$(cat .CIRCLECI_MERGE_COMMIT)"
+echo "export CIRCLECI_MERGE_COMMIT=$CIRCLECI_MERGE_COMMIT" >> $BASH_ENV
 
-export CIRCLE_MERGE_SHA="$(cat .CIRCLECI_WORKFLOW_MERGE_COMMIT)"
-echo $(GREEN "Fetching merge commit $CIRCLE_MERGE_SHA...")
-(set -x && git pull --ff-only origin "$CIRCLE_MERGE_SHA") || err=$?
+# Fetch the merge commit. This ensures that all CI stages use the same commit.
+echo $(GREEN "Fetching merge commit $CIRCLECI_MERGE_COMMIT...")
+(set -x && git pull --ff-only origin "$CIRCLECI_MERGE_COMMIT") || err=$?
 
 # If a clean merge is not possible, do not proceed with the build. GitHub's UI
 # will show an error indicating there was a merge conflict.

.circleci/get_pr_number.sh

@@ -0,0 +1,55 @@
+#!/bin/bash
+#
+# Copyright 2021 The AMP HTML Authors. All Rights Reserved.
+#
+# 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.
+
+# This script extracts the PR number (if there is one) for a CircleCI build.
+# Reference: https://circleci.com/docs/2.0/env-vars/#built-in-environment-variables
+
+set -e
+err=0
+
+GREEN() { echo -e "\n\033[0;32m$1\033[0m"; }
+YELLOW() { echo -e "\n\033[0;33m$1\033[0m"; }
+
+# Push builds are only run against master and amp-release branches.
+if [[ "$CIRCLE_BRANCH" == "master" || "$CIRCLE_BRANCH" =~ ^amp-release-* ]]; then
+  echo $(GREEN "Nothing to do because $CIRCLE_BRANCH is not a PR branch.")
+  # Warn if the build is linked to a PR on a different repo (known CircleCI bug).
+  if [[ -n "$CIRCLE_PULL_REQUEST" && ! "$CIRCLE_PULL_REQUEST" =~ ^https://github.com/ampproject/amphtml* ]]; then
+    echo $(YELLOW "WARNING: Build is incorrectly linked to a PR outside ampproject/amphtml:")
+    echo $(YELLOW "$CIRCLE_PULL_REQUEST")
+  fi
+  exit 0
+fi
+
+# CIRCLE_PR_NUMBER is present for PRs originating from forks, but absent for PRs
+# originating from a branch on the main repo. In such cases, extract the PR
+# number from CIRCLE_PULL_REQUEST.
+if [[ "$CIRCLE_PR_NUMBER" ]]; then
+  PR_NUMBER=$CIRCLE_PR_NUMBER
+else
+  PR_NUMBER=${CIRCLE_PULL_REQUEST#"https://github.com/ampproject/amphtml/pull/"}
+fi
+
+# If neither CIRCLE_PR_NUMBER nor CIRCLE_PULL_REQUEST are available, it's
+# possible this is a PR branch that is yet to be associated with a PR. Exit
+# early becaue there is no merge commit to fetch.
+if [[ -z "$PR_NUMBER" ]]; then
+  echo $(GREEN "Nothing to do because $CIRCLE_BRANCH is not yet linked to a PR.")
+  exit 0
+fi
+
+echo "export PR_NUMBER=$PR_NUMBER" >> $BASH_ENV
+echo $(GREEN "This is a PR build for #$PR_NUMBER.")

.gitignore

@@ -1,6 +1,6 @@
 .DS_Store
 .g4ignore
-.CIRCLECI_WORKFLOW_MERGE_COMMIT
+.CIRCLECI_MERGE_COMMIT
 build/
 .amp-dep-check
 c

build-system/common/ci.js

@@ -195,12 +195,12 @@ function ciJobUrl() {
 }
 
 /**
- * Returns the merge commits SHA when running a CI Pull Request build.
+ * Returns the merge commit for a CircleCI PR build. CIRCLECI_MERGE_COMMIT is
+ * populated by .circleci/fetch_merge_commit.sh.
  * @return {string}
  */
-function circleciPrMergeSha() {
-  // CIRCLE_MERGE_SHA is populated by .circleci/fetch_merge_commit.sh.
-  return isCircleci ? env('CIRCLE_MERGE_SHA') : '';
+function circleciPrMergeCommit() {
+  return isCircleci ? env('CIRCLECI_MERGE_COMMIT') : '';
 }
 
 /**
@@ -230,10 +230,10 @@ module.exports = {
   ciCommitSha,
   ciJobId,
   ciJobUrl,
-  circleciPrMergeSha,
   ciPullRequestBranch,
   ciPullRequestSha,
   ciPushBranch,
+  circleciPrMergeCommit,
   ciRepoSlug,
   isCiBuild,
   isCircleciBuild,

build-system/tasks/bundle-size/index.js

@@ -29,8 +29,8 @@ const {
   isPullRequestBuild,
   isPushBuild,
   ciPushBranch,
+  circleciPrMergeCommit,
   ciRepoSlug,
-  circleciPrMergeSha,
 } = require('../../common/ci');
 const {
   VERSION: internalRuntimeVersion,
@@ -171,24 +171,27 @@ async function skipBundleSize() {
  */
 async function reportBundleSize() {
   if (isPullRequestBuild()) {
+    const headSha = gitCommitHash();
     const baseSha = gitCiMasterBaseline();
-    const commitHash = gitCommitHash();
+    const mergeSha = circleciPrMergeCommit();
     log(
       'Reporting bundle sizes for commit',
-      cyan(shortSha(commitHash)),
+      cyan(shortSha(headSha)),
       'using baseline commit',
-      cyan(shortSha(baseSha)) + '...'
+      cyan(shortSha(baseSha)),
+      'and merge commit',
+      cyan(shortSha(mergeSha)) + '...'
     );
     try {
       const response = await requestPost({
         uri: url.resolve(
           bundleSizeAppBaseUrl,
-          path.join('commit', commitHash, 'report')
+          path.join('commit', headSha, 'report')
         ),
         json: true,
         body: {
           baseSha,
-          mergeSha: circleciPrMergeSha(),
+          mergeSha,
           bundleSizes: await getBrotliBundleSizes(),
         },
       });