feat(core): add utility for merge config function

core/deps.ts

@@ -51,6 +51,7 @@ export function prop<
 export type Arrayable<T> = T | T[];
 export { deepMerge } from "https://deno.land/std@0.122.0/collections/deep_merge.ts";
 export { distinctBy } from "https://deno.land/std@0.125.0/collections/distinct_by.ts";
+export { mapEntries } from "https://deno.land/std@0.125.0/collections/map_entries.ts";
 export function wrap<T>(val: T): T extends any[] ? T : T[] {
   return Array.isArray(val) ? val as never : [val] as never;
 }

core/mod.ts

@@ -10,3 +10,4 @@ export * from "./resolve.ts";
 export * from "./types.ts";
 export * from "./ast.ts";
 export * from "./transform.ts";
+export * from "./util.ts";

core/util.ts

@@ -0,0 +1,23 @@
+import { Config } from "./types.ts";
+import { deepMerge, mapEntries, wrap } from "./deps.ts";
+
+/** merge two config.
+ * if it exists arrayable property, the value will wrap array and merge.
+ */
+export function mergeConfig(a: Config, b: Config): Config {
+  const arrayables = ["css", "extractor"];
+
+  return deepMerge(wrapArray(a, arrayables), wrapArray(b, arrayables), {
+    arrays: "merge",
+  });
+}
+
+function wrapArray<T extends Record<PropertyKey, unknown>>(
+  value: T,
+  keys: string[],
+): T {
+  return mapEntries(value, ([key, value]) => {
+    const v = keys.includes(key) ? wrap(value) : value;
+    return [key, v];
+  }) as T;
+}

core/util_test.ts

@@ -0,0 +1,64 @@
+import { mergeConfig } from "./util.ts";
+import { anyFunction, expect, ParamReturn } from "../dev_deps.ts";
+
+Deno.test("mergeConfig", () => {
+  const table: ParamReturn<typeof mergeConfig>[] = [
+    [{}, {}, {}],
+    [
+      {
+        css: {},
+      },
+      { css: {} },
+      {
+        css: [{}, {}],
+      },
+    ],
+    [
+      {
+        css: { a: {} },
+      },
+      { css: [{}] },
+      {
+        css: [{ a: {} }, {}],
+      },
+    ],
+    [
+      {
+        css: { a: {} },
+      },
+      {
+        cssMap: {
+          block: { display: "block" },
+        },
+      },
+      {
+        cssMap: {
+          block: { display: "block" },
+        },
+        css: [{ a: {} }],
+      },
+    ],
+    [
+      {
+        preset: [{
+          name: "preset1",
+          fn: () => ({}),
+        }],
+      },
+      {
+        preset: [{
+          name: "preset2",
+          fn: () => ({}),
+        }],
+      },
+      {
+        preset: [
+          { name: "preset1", fn: anyFunction() as any },
+          { name: "preset2", fn: anyFunction() as any },
+        ],
+      },
+    ],
+  ];
+
+  table.forEach(([a, b, result]) => expect(mergeConfig(a, b)).toEqual(result));
+});