Add pre-commit and ./fmt.sh --test checks for yarn.lock file (#18112)

* Add yarn-lock-check pre-commit check

* Invoke yarn-lock-check pre-commit check from './fmt.sh --test'

* Run yarn-lock-check when yarn.lock changes

.pre-commit-config.yaml

@@ -51,6 +51,12 @@ repos:
       language: system
       pass_filenames: false
       entry: "pre-commit/platform-independence-check.sh"
+    - id: yarn-lock-check
+      name: yarn-lock-check
+      language: system
+      pass_filenames: false
+      files: ^(package.json|yarn.lock)$
+      entry: "pre-commit/yarn-lock-check.sh"
     - id: mainonly
       name: main only
       description: Check for changes under packages with targets tagged with main-only

fmt.sh

@@ -129,6 +129,13 @@ echo "\
 ──██────▐█▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓█▌
 "
 
+# In 'test' mode, this checks that the 'yarn.lock' file doesn't need any changes.
+# In 'format' mode, the 'yarn.lock' file will be updated ("formatted") by
+# 'yarn install' below, if needed.
+if [[ $is_test = 1 ]]; then
+  run pre-commit run yarn-lock-check
+fi
+
 # Make sure the current packages are installed so we can call pprettier
 # via yarn because calling it via bazel results in very bad performance.
 run yarn install --silent

pre-commit/yarn-lock-check.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# Copyright (c) 2023 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+set -euo pipefail
+
+TMP_DIR=$(mktemp -d)
+cp package.json yarn.lock $TMP_DIR
+
+(cd $TMP_DIR; yarn install --silent > /dev/null)
+
+if ! diff yarn.lock $TMP_DIR/yarn.lock; then
+    echo "FAIL: yarn.lock could not satisfy package.json" 1>&2
+    echo "FAIL: yarn.lock requires all of the above changes" 1>&2
+    exit 1
+fi