Add ESM wrapper to avoid dual package hazard

packages/protobuf/package.json

@@ -8,24 +8,22 @@
     "url": "https://github.com/bufbuild/protobuf-es.git",
     "directory": "packages/protobuf"
   },
-  "sideEffects": false,
   "scripts": {
-    "clean": "rm -rf ./dist/cjs/* ./dist/esm/*",
-    "build": "npm run build:cjs && npm run build:esm",
+    "clean": "rm -rf ./dist/*",
+    "build": "npm run build:cjs && npm run build:esm && npm run build:proxy",
     "build:cjs": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module commonjs --outDir ./dist/cjs --declaration --declarationDir ./dist/cjs && echo >./dist/cjs/package.json '{\"type\":\"commonjs\"}'",
     "build:esm": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module ES2015 --verbatimModuleSyntax --outDir ./dist/esm --declaration --declarationDir ./dist/esm",
+    "build:proxy": "node ../../scripts/gen-esm-proxy.mjs .",
     "attw": "attw --pack"
   },
-  "main": "./dist/cjs/index.js",
   "type": "module",
+  "sideEffects": false,
+  "main": "./dist/cjs/index.js",
   "exports": {
-    "import": {
-      "types": "./dist/esm/index.d.ts",
-      "default": "./dist/esm/index.js"
-    },
-    "require": {
-      "types": "./dist/cjs/index.d.ts",
-      "default": "./dist/cjs/index.js"
+    ".": {
+      "module": "./dist/esm/index.js",
+      "require": "./dist/cjs/index.js",
+      "import": "./dist/proxy/index.js"
     }
   },
   "files": [

packages/protoplugin/package.json

@@ -8,36 +8,27 @@
     "url": "https://github.com/bufbuild/protobuf-es.git",
     "directory": "packages/protoplugin"
   },
-  "sideEffects": false,
   "scripts": {
-    "clean": "rm -rf ./dist/cjs/* ./dist/esm/*",
-    "build": "npm run build:cjs && npm run build:esm",
+    "clean": "rm -rf ./dist/*",
+    "build": "npm run build:cjs && npm run build:esm && npm run build:proxy",
     "build:cjs": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module commonjs --outDir ./dist/cjs --declaration --declarationDir ./dist/cjs && echo >./dist/cjs/package.json '{\"type\":\"commonjs\"}'",
     "build:esm": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module ES2015 --outDir ./dist/esm --declaration --declarationDir ./dist/esm",
+    "build:proxy": "node ../../scripts/gen-esm-proxy.mjs . ecmascript",
     "attw": "attw --pack"
   },
-  "main": "./dist/cjs/index.js",
   "type": "module",
+  "sideEffects": false,
+  "main": "./dist/cjs/index.js",
   "exports": {
     ".": {
-      "import": {
-        "types": "./dist/esm/index.d.ts",
-        "default": "./dist/esm/index.js"
-      },
-      "require": {
-        "types": "./dist/cjs/index.d.ts",
-        "default": "./dist/cjs/index.js"
-      }
+      "module": "./dist/esm/index.js",
+      "require": "./dist/cjs/index.js",
+      "import": "./dist/proxy/index.js"
     },
     "./ecmascript": {
-      "import": {
-        "types": "./dist/esm/ecmascript/index.d.ts",
-        "default": "./dist/esm/ecmascript/index.js"
-      },
-      "require": {
-        "types": "./dist/cjs/ecmascript/index.d.ts",
-        "default": "./dist/cjs/ecmascript/index.js"
-      }
+      "module": "./dist/esm/ecmascript/index.js",
+      "require": "./dist/cjs/ecmascript/index.js",
+      "import": "./dist/proxy/ecmascript/index.js"
     }
   },
   "typesVersions": {

scripts/gen-esm-proxy.mjs

@@ -0,0 +1,103 @@
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
+import * as path from "node:path";
+import { exit, stderr, stdout, argv } from "node:process";
+
+const args = argv.slice(2);
+
+if (args.length === 0) {
+  stdout.write(`USAGE: ${path.basename(argv[1])} [...path]
+path: One or more subpath exports. A dot (.) is valid.
+
+Generates ESM wrappers for dual packages.
+
+Example:
+
+  ${path.basename(argv[1])} . foo
+
+Assumes that the following CJS artifacts exist: 
+
+  dist/cjs
+  ├── index.d.ts
+  ├── index.js
+  └── foo
+      ├── index.d.ts
+      └── index.js
+
+Generates the following ESM wrappers:
+
+  dist/proxy
+  ├── index.d.ts
+  ├── index.js
+  └── foo
+      ├── index.d.ts
+      └── index.js
+
+package.json must contain:
+
+  "type": "module", 
+  "exports": {
+    ".": {
+      "require": "./dist/cjs/index.js",
+      "import": "./dist/proxy/index.js"
+    },
+    "./protocol": {
+      "require": "./dist/cjs/foo/index.js",
+      "import": "./dist/proxy/foo/index.js"
+    },
+
+Known limitations:
+- expects CJS files with a .js extension, not .cjs
+- does not support default exports
+- supports only simple subpath directory exports, assuming a index.js file
+- does not support export patterns
+`);
+  exit(1);
+}
+
+const cjsDist = "dist/cjs";
+const proxyDist = "dist/proxy";
+
+const packageType = readPackageJsonType();
+if (packageType !== "module") {
+  stderr.write(`package.json is missing "type": "module" field.\n`);
+  exit(1);
+}
+
+for (const subpath of args) {
+  const cjsPath = path.join(cjsDist, subpath, "index.js");
+  if (!existsSync(cjsPath)) {
+    stderr.write(
+      `CommonJS artifact for subpath "${subpath}" not found at expected path ${cjsPath}\n`,
+    );
+    exit(1);
+  }
+  const proxyDir = path.join(proxyDist, subpath);
+  if (!existsSync(proxyDir)) {
+    mkdirSync(proxyDir, { recursive: true });
+  }
+  const cjsImportPath = path.relative(proxyDir, cjsPath);
+  writeFileSync(
+    path.join(proxyDir, "index.js"),
+    `export * from "${cjsImportPath}";\n`,
+  );
+  writeFileSync(
+    path.join(proxyDir, "index.d.ts"),
+    `export * from "${cjsImportPath}";\n`,
+  );
+}
+
+/**
+ * @return {"commonjs"|"module"}
+ */
+function readPackageJsonType() {
+  const pkgString = readFileSync("package.json", "utf-8");
+  const pkg = JSON.parse(pkgString);
+  const t = pkg.type;
+  if (typeof t !== "string") {
+    return "commonjs";
+  }
+  if (t.toLowerCase() === "module") {
+    return "module";
+  }
+  return "commonjs";
+}