From 4e56826b1a4cfef7abcde99d19b766f80d9dee66 Mon Sep 17 00:00:00 2001
From: Boris Serdiuk <serdiuk@amazon.com>
Date: Mon, 25 Mar 2024 18:18:39 +0100
Subject: [PATCH] feat: Add merge utility

---
 README.md          |  6 ++--
 merge.js           | 13 ++++++++
 package-lock.json  |  4 +--
 package.json       |  3 +-
 test/merge.test.js | 79 ++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 99 insertions(+), 6 deletions(-)
 create mode 100644 merge.js
 create mode 100644 test/merge.test.js

diff --git a/README.md b/README.md
index ed5696f..fa641d6 100644
--- a/README.md
+++ b/README.md
@@ -40,14 +40,14 @@ In your `jest.config.json`:
 
 ### Advanced usage
 
-If you are already have another preset in your configuration, you can [merge them together](https://stackoverflow.com/questions/51002460/is-it-possible-to-use-jest-with-multiple-presets-at-the-same-time):
+If you are already have another preset in your configuration, you can use `@cloudscape-design/jest-preset/merge` helper to merge them together:
 
 ```js
-const merge = require('merge');
+const mergePresets = require('@cloudscape-design/jest-preset/merge');
 const tsPreset = require('ts-jest/jest-preset');
 const cloudscapePreset = require('@cloudscape-design/jest-preset');
 
-module.exports = merge.recursive(tsPreset, cloudscapePreset, {
+module.exports = mergePresets(tsPreset, cloudscapePreset, {
   // ... your config
 });
 ```
diff --git a/merge.js b/merge.js
new file mode 100644
index 0000000..ab61035
--- /dev/null
+++ b/merge.js
@@ -0,0 +1,13 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+const { mergeWith } = require('lodash');
+
+function mergeArrays(dest, src) {
+  if (Array.isArray(dest)) {
+    return dest.concat(src);
+  }
+}
+
+module.exports = function mergePresets(...presets) {
+  return mergeWith({}, ...presets, mergeArrays);
+};
diff --git a/package-lock.json b/package-lock.json
index e44dc0a..6c63db0 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -8,7 +8,8 @@
       "name": "@cloudscape-design/jest-preset",
       "version": "2.0.0",
       "dependencies": {
-        "@babel/plugin-transform-modules-commonjs": "^7.9.0"
+        "@babel/plugin-transform-modules-commonjs": "^7.9.0",
+        "lodash": "^4.17.21"
       },
       "devDependencies": {
         "eslint": "^8.56.0",
@@ -6165,7 +6166,6 @@
     },
     "node_modules/lodash": {
       "version": "4.17.21",
-      "dev": true,
       "license": "MIT"
     },
     "node_modules/lodash.merge": {
diff --git a/package.json b/package.json
index bcc746c..7a83771 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,8 @@
     "jest": ">=24"
   },
   "dependencies": {
-    "@babel/plugin-transform-modules-commonjs": "^7.9.0"
+    "@babel/plugin-transform-modules-commonjs": "^7.9.0",
+    "lodash": "^4.17.21"
   },
   "devDependencies": {
     "eslint": "^8.56.0",
diff --git a/test/merge.test.js b/test/merge.test.js
new file mode 100644
index 0000000..3bb0830
--- /dev/null
+++ b/test/merge.test.js
@@ -0,0 +1,79 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+const tap = require('tap');
+const { strict: assert } = require('assert');
+const merge = require('../merge');
+
+tap.test('merging simple configurations', t => {
+  assert.deepEqual(
+    merge(
+      {
+        transformIgnorePatterns: ['project-ignore'],
+        transform: {
+          'project-js': 'project-babel-jest',
+        },
+      },
+      {
+        transformIgnorePatterns: ['our-ignore'],
+        transform: {
+          'cloudscape-js': 'our-babel-jest',
+        },
+      },
+    ),
+    {
+      transform: {
+        'project-js': 'project-babel-jest',
+        'cloudscape-js': 'our-babel-jest',
+      },
+      transformIgnorePatterns: ['project-ignore', 'our-ignore'],
+    },
+  );
+  t.end();
+});
+
+tap.test('merging multiple configurations', t => {
+  assert.deepEqual(
+    merge(
+      {
+        transform: { 'project-js': 'project-babel-jest' },
+      },
+      {
+        transform: { 'project-ts': 'ts-transformer' },
+      },
+
+      {
+        transform: { 'cloudscape-js': 'our-babel-jest' },
+      },
+    ),
+    {
+      transform: {
+        'project-js': 'project-babel-jest',
+        'project-ts': 'ts-transformer',
+        'cloudscape-js': 'our-babel-jest',
+      },
+    },
+  );
+  t.end();
+});
+
+tap.test('does not mutate objects', t => {
+  const src = {
+    transform: { 'project-js': 'project-babel-jest' },
+  };
+  const dest = {
+    transform: { 'cloudscape-js': 'our-babel-jest' },
+  };
+  assert.deepEqual(merge(src, dest), {
+    transform: {
+      'project-js': 'project-babel-jest',
+      'cloudscape-js': 'our-babel-jest',
+    },
+  });
+  assert.deepEqual(src, {
+    transform: { 'project-js': 'project-babel-jest' },
+  });
+  assert.deepEqual(dest, {
+    transform: { 'cloudscape-js': 'our-babel-jest' },
+  });
+  t.end();
+});