chore: add merge function with tests (#81)

- Implement a `merge` function to combine two objects
- Add unit tests to `merge` function

packages/tailwindcss-core/src/generate-classes.ts

@@ -3,6 +3,7 @@ import tailwindcss from "tailwindcss"
 import minify from "@csstools/postcss-minify"
 import { PluginsConfig } from "tailwindcss/types/config.js"
 import { FlattenArrayType } from "@halvaradop/ts-utility-types"
+import { isObject, isPrimitive } from "@halvaradop/ts-utility-types/utils"
 
 const TAILWIND_UTILITIES_DIRECTIVE = "@tailwind utilities;"
 
@@ -32,3 +33,31 @@ export const extractClasses = (plugin: FlattenArrayType<PluginsConfig>) => {
     }
     return generateCSS
 }
+
+/**
+ * Create a new object by merging two objects which prioritize the object types
+ *
+ * @param source first object to merge
+ * @param target second object to merge
+ * @param priority true if the object type should be prioritized, false otherwise
+ * @returns merged two objects
+ */
+export const merge = <S extends Record<string, unknown>, T extends Record<string, unknown>>(
+    source: S,
+    target: T,
+    priority: boolean = true
+) => {
+    if (priority && isPrimitive(source) && isObject(target)) return target
+    if (priority && isPrimitive(target) && isObject(source)) return source
+    const merged: Record<string, unknown> = { ...source }
+    for (const key in target) {
+        if (!isObject(target[key])) {
+            if ((priority && !isObject(source[key])) || !priority) {
+                merged[key] = target[key]
+            } 
+        } else {
+            merged[key] = merge(source[key] as S, target[key] as T, priority)
+        }
+    }
+    return merged
+}

packages/tailwindcss-core/test/index.test.ts

@@ -1,5 +1,5 @@
 import { describe, test, expect } from "vitest"
-import { extractClasses } from "../src/generate-classes"
+import { extractClasses, merge } from "../src/generate-classes"
 
 /**
  * Provide a mock implementation of the extractClasses function with an
@@ -30,3 +30,48 @@ describe("Extract classes from tailwindcss", () => {
         expect(css).toMatch(".text-lg{font-size:1.125rem;line-height:1.75rem}")
     })
 })
+
+describe("Merge objects", () => {
+    test("Merge two objects", () => {
+        const source = { a: 1, b: 2 }
+        const target = { b: 3, c: 4 }
+        expect(merge(source, target)).toEqual({ a: 1, b: 3, c: 4 })
+    })
+
+    test("Merge two objects with nested objects", () => {
+        const source = { a: 1, b: { c: 2 } }
+        const target = { b: 3, c: 4 }
+        expect(merge(source, target)).toEqual({ a: 1, b: { c: 2 }, c: 4 })
+    })
+
+    test("Merge two objects with nested objects and nested objects", () => {
+        const source = { a: 1, b: { c: 2 } }
+        const target = { b: { c: 3 }, c: 4 }
+        expect(merge(source, target)).toEqual({ a: 1, b: { c: 3 }, c: 4 })
+    })
+
+    test("Merge two objects with nested objects and nested objects with different keys", () => {
+        const source = { a: 1, b: { c: 2 } }
+        const target = { b: { d: 3 }, c: 4 }
+        expect(merge(source, target)).toEqual({ a: 1, b: { c: 2, d: 3 }, c: 4 })
+    })
+
+    test("Merge two objects with nested objects and nested objects with different keys and nested objects", () => {
+        const source = { a: 1, b: { c: 2, d: { e: 3 } } }
+        const target = { b: { d: 4 }, c: 5 }
+        expect(merge(source, target)).toEqual({ a: 1, b: { c: 2, d: { e: 3 } }, c: 5 })
+    })
+
+    test("Merge two objects with nested objects and nested objects with different keys and nested objects with different keys", () => {
+        const source = { a: 1, b: { c: 2, d: { e: 3 } } }
+        const target = { b: { d: { f: 4 } }, c: 5 }
+        expect(merge(source, target)).toEqual({ a: 1, b: { c: 2, d: { e: 3, f: 4 } }, c: 5 })
+    })
+
+    test("Merge two object with nested object and nested object without priority", () => {
+        const source = { a: 1, b: { c: 2, d: { e: 3 } } }
+        const target = { b: { d: 4 }, c: 5 }
+        expect(merge(source, target, false)).toEqual({ a: 1, b: { c: 2, d: 4 }, c: 5 })
+    })
+
+})