[e18e]: Replace lodash/merge & lodash/mergeWith with an alternative

code/builders/builder-vite/src/optimizeDeps.ts

@@ -52,10 +52,6 @@ const INCLUDE_CANDIDATES = [
   'lodash/mapKeys',
   'lodash/mapValues.js',
   'lodash/mapValues',
-  'lodash/merge.js',
-  'lodash/merge',
-  'lodash/mergeWith.js',
-  'lodash/mergeWith',
   'lodash/pick.js',
   'lodash/pick',
   'lodash/pickBy.js',

code/core/package.json

@@ -257,6 +257,7 @@
     "@types/express": "^4.17.21",
     "@types/node": "^18.0.0",
     "browser-assert": "^1.2.1",
+    "defu": "^6.1.4",
     "esbuild": "^0.18.0 || ^0.19.0 || ^0.20.0 || ^0.21.0 || ^0.22.0 || ^0.23.0",
     "esbuild-register": "^3.5.0",
     "express": "^4.19.2",

code/core/src/manager-api/lib/merge.test.ts

@@ -0,0 +1,15 @@
+import { test, describe } from "vitest";
+
+import merge from "./merge";
+
+describe(merge.name, () => {
+  test("applies entries not in the source", ({ expect }) => {
+    const merged = merge({ a: 1 }, { a: 2, b: 3, c: 4 });
+    console.log({ merged });
+    expect(merged).toStrictEqual({
+      a: 1,
+      b: 3,
+      c: 4
+    });
+  });
+});

code/core/src/manager-api/lib/merge.ts

@@ -1,23 +1,19 @@
-import mergeWith from 'lodash/mergeWith.js';
-import isEqual from 'lodash/isEqual.js';
+import { defu, defuArrayFn } from 'defu';
 
 import { logger } from '@storybook/core/client-logger';
 
-export default <TObj = any>(a: TObj, b: Partial<TObj>) =>
-  mergeWith({}, a, b, (objValue: TObj, srcValue: Partial<TObj>) => {
-    if (Array.isArray(srcValue) && Array.isArray(objValue)) {
-      srcValue.forEach((s) => {
-        const existing = objValue.find((o) => o === s || isEqual(o, s));
-        if (!existing) {
-          objValue.push(s);
-        }
-      });
-
-      return objValue;
-    }
-    if (Array.isArray(objValue)) {
-      logger.log(['the types mismatch, picking', objValue]);
-      return objValue;
+export default <TObj = any>(a: TObj, b: Partial<TObj> & any) => {
+  if (Array.isArray(a)) {
+    if (Array.isArray(b)) {
+      return defuArrayFn(a, b);
     }
-    return undefined;
-  });
+
+    logger.log(['the types mismatch, picking', a]);
+    return a;
+  }
+
+  // TODO: Ask for what is prefered:
+  // 1. type guard (safe at runtime, but potential performance slow-down)
+  // 2. or type assertion (unsafe at runtime)
+  return defu(a as object, b);
+};