Add extra processing options

src/esbuild-babel.ts

@@ -0,0 +1,51 @@
+import { readFileSync } from "node:fs";
+import { extname } from "node:path";
+import { once } from "lodash";
+import type babel from "@babel/core";
+import type * as esbuild from "esbuild";
+import { transformSync } from "@babel/core";
+
+/**
+ * An esbuild plugin that processes files with Babel if `getPlugins` returns any plugins.
+ */
+export const babelPlugin = ({
+  filter = /\.[jt]sx?$/,
+  plugins: getPlugins,
+}: {
+  filter?: RegExp;
+  plugins:
+    | babel.PluginItem[]
+    | ((file: { path: string; contents: string }) => babel.PluginItem[]);
+}): esbuild.Plugin => ({
+  name: "babel-plugin",
+  setup(build) {
+    build.onLoad({ filter }, ({ path }) => {
+      const load = once(() => readFileSync(path, "utf-8"));
+      const plugins = Array.isArray(getPlugins)
+        ? getPlugins
+        : getPlugins({
+            path,
+            get contents() {
+              return load();
+            },
+          });
+
+      if (!plugins.length) {
+        return;
+      }
+
+      const { code } = transformSync(load(), {
+        parserOpts: {
+          plugins: ["jsx", "decorators", "typescript", "importAttributes"],
+        },
+        filename: path,
+        plugins,
+      })!;
+
+      return {
+        contents: code!,
+        loader: extname(path).slice(1) as "js" | "ts",
+      };
+    });
+  },
+});