feat: replace postcss-load-config with custom implementation

src/loaders/postcss/config.ts

@@ -0,0 +1,53 @@
+import path from "path";
+import postcss from "postcss";
+import { cosmiconfig } from "cosmiconfig";
+import { PostCSSConfigLoaderOptions } from "../../types";
+import { ensurePCSSPlugins, ensurePCSSOption } from "../../utils/options";
+
+interface Options {
+  parser?: postcss.Parser;
+  syntax?: postcss.Syntax;
+  stringifier?: postcss.Stringifier;
+}
+
+interface Config extends Options {
+  plugins?: { [p: string]: Record<string, unknown> };
+}
+
+interface Result {
+  plugins: (postcss.Transformer | postcss.Processor)[];
+  options: Options;
+}
+
+export default async function (
+  id: string,
+  config: false | PostCSSConfigLoaderOptions,
+): Promise<Result> {
+  if (!config) return { plugins: [], options: {} };
+
+  const { ext, dir, base } = path.parse(id);
+
+  type Found = { config: Config | ((ctx: Record<string, unknown>) => Config); isEmpty?: boolean };
+  const searchPath = config.path ? path.resolve(config.path) : dir;
+  const found: Found | null = await cosmiconfig("postcss").search(searchPath);
+
+  if (!found || found.isEmpty) return { plugins: [], options: {} };
+
+  const { plugins: _plugins, parser, syntax, stringifier } =
+    typeof found.config === "function"
+      ? found.config({
+          cwd: process.cwd(),
+          env: process.env["NODE_ENV"] ?? "development",
+          file: { extname: ext, dirname: dir, basename: base },
+          options: config.ctx ?? {},
+        })
+      : found.config;
+
+  const plugins = _plugins && Object.entries(_plugins);
+  const result: Result = { plugins: ensurePCSSPlugins(plugins), options: {} };
+  if (parser) result.options.parser = ensurePCSSOption(parser, "parser");
+  if (syntax) result.options.syntax = ensurePCSSOption(syntax, "syntax");
+  if (stringifier) result.options.stringifier = ensurePCSSOption(stringifier, "stringifier");
+
+  return result;
+}