Use ESM entrypoint for require(ESM) (#16958)

Co-authored-by: fisker Cheung <lionkay@gmail.com>

changelog_unreleased/misc/16958.md

@@ -0,0 +1,5 @@
+#### Use ESM entrypoint for `require(ESM)` (#16958 by @tats-u)
+
+Node.js 22.12 or later [can (experimentally) load ESM modules with `require` function](https://nodejs.org/api/modules.html#loading-ecmascript-modules-using-require) without runtime flags. This change enables `require` to load Prettier without the CommonJS entrypoint with almost only the ability to import the ESM entrypoint.
+
+The feature to load ES modules with `require` is not completely stable but can be used without ExperimentalWarning as of Node 22.13.

package.json

@@ -15,6 +15,7 @@
   "exports": {
     ".": {
       "types": "./src/index.d.ts",
+      "module-sync": "./src/index.js",
       "require": "./src/index.cjs",
       "default": "./src/index.js"
     },

scripts/build/build-package-json.js

@@ -42,6 +42,7 @@ async function buildPackageJson({ file, files }) {
     exports: {
       ".": {
         types: "./index.d.ts",
+        "module-sync": "./index.mjs",
         require: "./index.cjs",
         browser: {
           import: "./standalone.mjs",
@@ -55,12 +56,14 @@ async function buildPackageJson({ file, files }) {
           .filter((file) => file.output.format === "umd")
           .map((file) => {
             const basename = path.basename(file.output.file, ".js");
+            const mjsPath = `./${file.output.file.replace(/\.js$/u, ".mjs")}`;
             return [
               file.isPlugin ? `./plugins/${basename}` : `./${basename}`,
               {
                 types: `./${file.output.file.replace(/\.js$/u, ".d.ts")}`,
+                "module-sync": mjsPath,
                 require: `./${file.output.file}`,
-                default: `./${file.output.file.replace(/\.js$/u, ".mjs")}`,
+                default: mjsPath,
               },
             ];
           }),