chore(esm-post-process): import extensions for files only, .d.ts supp…

…ort and cleanup

package.json

@@ -81,7 +81,7 @@
     "test": "jest",
     "bench:start-servers": "NODE_ENV=production node benchmark/servers/index.mjs",
     "bench": "k6 run benchmark/k6.mjs",
-    "build:esm": "tsc -b tsconfig.esm.json && node scripts/esm-post-process.js",
+    "build:esm": "tsc -b tsconfig.esm.json && node scripts/esm-post-process.mjs",
     "build:cjs": "tsc -b tsconfig.cjs.json",
     "build:umd": "rollup -c && gzip umd/graphql-ws.min.js -c > umd/graphql-ws.min.js.gz",
     "build": "yarn build:esm && yarn build:cjs && yarn build:umd",

scripts/esm-post-process.mjs

@@ -0,0 +1,66 @@
+// @ts-check
+
+import fs from 'fs/promises';
+import path from 'path';
+import glob from 'glob';
+
+const rootDir = 'lib';
+
+glob(`${rootDir}/**/*.js`, async (_, matches) => {
+  for (const path of matches) {
+    await buildEsm(path);
+  }
+
+  // we delete after build to not mess with import/export statement replacer
+  for (const path of matches) {
+    await fs.unlink(path);
+  }
+});
+
+glob(`${rootDir}/**/*.d.ts`, async (_, matches) => {
+  for (const path of matches) {
+    await buildEsm(path);
+  }
+
+  // we dont delete raw d.ts files, they're still needed for imports/exports
+});
+
+/**
+ * @param {string} filePath
+ */
+async function buildEsm(filePath) {
+  const pathParts = filePath.split('.');
+  const fileExt = pathParts.pop();
+
+  const file = await fs.readFile(path.join(process.cwd(), filePath));
+  let content = file.toString();
+
+  if (fileExt === 'js') {
+    // add .mjs to all import/export statements, but only on files (keep directory imports as is)
+    for (const match of content.matchAll(/from '(\.?\.\/[^']*)'/g)) {
+      const [statement, relImportPath] = match;
+      const absImportPath = path.resolve(
+        process.cwd(),
+        path.dirname(filePath),
+        relImportPath,
+      );
+
+      try {
+        await fs.stat(absImportPath + '.js');
+
+        // file import
+        content = content.replace(statement, `from '${relImportPath}.mjs'`);
+      } catch {
+        // directory import
+        content = content.replace(
+          statement,
+          `from '${relImportPath}/index.mjs'`,
+        );
+      }
+    }
+  }
+
+  // write to file with prepended "m" in extension (.js -> .mjs, .ts -> .mts)
+  const esmFilePath = pathParts.join('.') + '.m' + fileExt;
+  await fs.writeFile(esmFilePath, content);
+}