feat(dev-infra): save invalid commit message attempts to be restored on next commit attempt (#38304)

When a commit message fails validation, rather than throwing out the commit message entirely
the commit message is saved into a draft file and restored on the next commit attempt.

PR Close #38304

dev-infra/commit-message/BUILD.bazel

@@ -5,8 +5,10 @@ ts_library(
     name = "commit-message",
     srcs = [
         "cli.ts",
+        "commit-message-draft.ts",
         "config.ts",
         "parse.ts",
+        "restore-commit-message.ts",
         "validate.ts",
         "validate-file.ts",
         "validate-range.ts",

dev-infra/commit-message/cli.ts

@@ -9,6 +9,7 @@ import * as yargs from 'yargs';
 
 import {info} from '../utils/console';
 
+import {restoreCommitMessage} from './restore-commit-message';
 import {validateFile} from './validate-file';
 import {validateCommitRange} from './validate-range';
 
@@ -16,6 +17,28 @@ import {validateCommitRange} from './validate-range';
 export function buildCommitMessageParser(localYargs: yargs.Argv) {
   return localYargs.help()
       .strict()
+      .command(
+          'restore-commit-message-draft', false, {
+            'file-env-variable': {
+              type: 'string',
+              conflicts: ['file'],
+              required: true,
+              description:
+                  'The key for the environment variable which holds the arguments for the ' +
+                  'prepare-commit-msg hook as described here: ' +
+                  'https://git-scm.com/docs/githooks#_prepare_commit_msg',
+              coerce: arg => {
+                const [file, source] = (process.env[arg] || '').split(' ');
+                if (!file) {
+                  throw new Error(`Provided environment variable "${arg}" was not found.`);
+                }
+                return [file, source];
+              },
+            }
+          },
+          args => {
+            restoreCommitMessage(args.fileEnvVariable[0], args.fileEnvVariable[1]);
+          })
       .command(
           'pre-commit-validate', 'Validate the most recent commit message', {
             'file': {

dev-infra/commit-message/commit-message-draft.ts

@@ -0,0 +1,30 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+import {existsSync, readFileSync, unlinkSync, writeFileSync} from 'fs';
+
+/** Load the commit message draft from the file system if it exists. */
+export function loadCommitMessageDraft(basePath: string) {
+  const commitMessageDraftPath = `${basePath}.ngDevSave`;
+  if (existsSync(commitMessageDraftPath)) {
+    return readFileSync(commitMessageDraftPath).toString();
+  }
+  return '';
+}
+
+/** Remove the commit message draft from the file system. */
+export function deleteCommitMessageDraft(basePath: string) {
+  const commitMessageDraftPath = `${basePath}.ngDevSave`;
+  if (existsSync(commitMessageDraftPath)) {
+    unlinkSync(commitMessageDraftPath);
+  }
+}
+
+/** Save the commit message draft to the file system for later retrieval. */
+export function saveCommitMessageDraft(basePath: string, commitMessage: string) {
+  writeFileSync(`${basePath}.ngDevSave`, commitMessage);
+}

dev-infra/commit-message/restore-commit-message.ts

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {info} from 'console';
+import {writeFileSync} from 'fs';
+
+import {loadCommitMessageDraft} from './commit-message-draft';
+
+/**
+ * Restore the commit message draft to the git to be used as the default commit message.
+ *
+ * The source provided may be one of the sources described in
+ *   https://git-scm.com/docs/githooks#_prepare_commit_msg
+ */
+export function restoreCommitMessage(
+    filePath: string, source?: 'message'|'template'|'squash'|'commit') {
+  if (!!source) {
+    info('Skipping commit message restoration attempt');
+    if (source === 'message') {
+      info('A commit message was already provided via the command with a -m or -F flag');
+    }
+    if (source === 'template') {
+      info('A commit message was already provided via the -t flag or config.template setting');
+    }
+    if (source === 'squash') {
+      info('A commit message was already provided as a merge action or via .git/MERGE_MSG');
+    }
+    if (source === 'commit') {
+      info('A commit message was already provided through a revision specified via --fixup, -c,');
+      info('-C or --amend flag');
+    }
+    process.exit(0);
+  }
+  /** A draft of a commit message. */
+  const commitMessage = loadCommitMessageDraft(filePath);
+
+  // If the commit message draft has content, restore it into the provided filepath.
+  if (commitMessage) {
+    writeFileSync(filePath, commitMessage);
+  }
+  // Exit the process
+  process.exit(0);
+}

dev-infra/commit-message/validate-file.ts

@@ -11,6 +11,7 @@ import {resolve} from 'path';
 import {getRepoBaseDir} from '../utils/config';
 import {info} from '../utils/console';
 
+import {deleteCommitMessageDraft, saveCommitMessageDraft} from './commit-message-draft';
 import {validateCommitMessage} from './validate';
 
 /** Validate commit message at the provided file path. */
@@ -18,8 +19,12 @@ export function validateFile(filePath: string) {
   const commitMessage = readFileSync(resolve(getRepoBaseDir(), filePath), 'utf8');
   if (validateCommitMessage(commitMessage)) {
     info('√  Valid commit message');
+    deleteCommitMessageDraft(filePath);
     return;
   }
+  // On all invalid commit messages, the commit message should be saved as a draft to be
+  // restored on the next commit attempt.
+  saveCommitMessageDraft(filePath, commitMessage);
   // If the validation did not return true, exit as a failure.
   process.exit(1);
 }

package.json

@@ -210,7 +210,8 @@
   "husky": {
     "hooks": {
       "pre-commit": "yarn -s ng-dev format staged",
-      "commit-msg": "yarn -s ng-dev commit-message pre-commit-validate --file-env-variable HUSKY_GIT_PARAMS"
+      "commit-msg": "yarn -s ng-dev commit-message pre-commit-validate --file-env-variable HUSKY_GIT_PARAMS",
+      "prepare-commit-msg": "yarn -s ng-dev commit-message restore-commit-message-draft --file-env-variable HUSKY_GIT_PARAMS"
     }
   }
 }