Implement externalized WASM build, fix nodejs#96

Author: mochaaP

build.js

@@ -1,73 +1,69 @@
 const fs = require('fs');
-const { buildSync } = require('esbuild');
-const path = require('path/posix')
+const esbuild = require('esbuild');
 
-const { EXTERNAL_PATH } = process.env;
-const MINIFY = !EXTERNAL_PATH;
+let minify = true;
+let cjsBuild = true;
+let esmBuild = true;
 
-try { fs.mkdirSync('./dist'); }
-catch (e) {}
+for (const arg of process.argv) {
+  switch (arg) {
+    case '--without-cjs': {
+      cjsBuild = false;
+      break;
+    }
+    case '--without-esm': {
+      esmBuild = false;
+      break;
+    }
+    case '--no-minify': {
+      minify = false;
+      break;
+    }
+    default:
+      continue;
+  }
+}
+
+fs.mkdirSync('./dist', { recursive: true });
 
 const wasmBuffer = fs.readFileSync('./lib/lexer.wasm');
 const pjson = JSON.parse(fs.readFileSync('./package.json').toString());
 
-buildSync({
+/** @type {esbuild.BuildOptions} */
+const buildOptions = {
   entryPoints: ['./src/lexer.js'],
-  outfile: './dist/lexer.mjs',
   bundle: true,
-  minify: MINIFY,
+  minify,
   platform: 'node',
-  format: 'esm',
   banner: {
-    js: `/* cjs-module-lexer ${pjson.version} */`
+    js: `/* cjs-module-lexer ${pjson.version} */`,
   },
-  define: EXTERNAL_PATH ? {
-    WASM_BINARY: 'undefined',
-    EXTERNAL_PATH: `'${path.join(EXTERNAL_PATH, 'lib/lexer.wasm')}'`,
-  } : {
+  outfile: './dist/lexer.mjs',
+  format: 'esm',
+  define: {
     WASM_BINARY: `'${wasmBuffer.toString('base64')}'`,
-    EXTERNAL_PATH: 'undefined'
-  }
-})
-
-if (EXTERNAL_PATH) {
-  buildSync({
-    stdin: {
-      contents: `'use strict';
-let lazy;
-async function init () {
-  if (!lazy) {
-    lazy = await import(require('node:url').pathToFileURL(require('node:module').createRequire('${EXTERNAL_PATH}/dist/lexer.js').resolve('./lexer.mjs')));
-  }
-  module.exports = lazy;
-  return lazy.init();
-}
-
-function parse (source, name = '@') {
-  if (!lazy)
-    throw new Error('Not initialized');
+  },
+};
 
-  return lazy.parse(source, name);
+if (esmBuild) {
+  // ESM builds are used when importing from npm.
+  // Assume lib/lexer.wasm exists.
+  esbuild.buildSync({
+    ...buildOptions,
+    define: {
+      WASM_BINARY: 'undefined',
+    },
+  });
 }
 
-module.exports = { init, parse };`,
-      loader: 'js',
-    },
+if (cjsBuild) {
+  // CJS builds are used for libnode inlined builtins.
+  esbuild.buildSync({
+    ...buildOptions,
     outfile: './dist/lexer.js',
-    minify: MINIFY,
-    platform: 'node',
     format: 'cjs',
+    logOverride: {
+      'empty-import-meta': 'silent'
+    },
   });
-} else {
-  buildSync({
-    entryPoints: ['./dist/lexer.mjs'],
-    outfile: './dist/lexer.js',
-    minify: MINIFY,
-    platform: 'node',
-    format: 'cjs',
-    banner: {
-      js: `/* cjs-module-lexer ${pjson.version} */`
-    }
-  })
 }
-

package.json

@@ -30,7 +30,8 @@
     "mocha": "^9.1.3"
   },
   "files": [
-    "dist",
+    "dist/",
+    "lib/lexer.wasm",
     "lexer.d.ts"
   ],
   "repository": {
@@ -41,4 +42,4 @@
     "url": "https://github.com/nodejs/cjs-module-lexer/issues"
   },
   "homepage": "https://github.com/nodejs/cjs-module-lexer#readme"
-}
+}

src/lexer.js

@@ -90,19 +90,26 @@ function copyLE (src, outBuf16) {
     outBuf16[i] = src.charCodeAt(i++);
 }
 
-const loadWasm = (typeof EXTERNAL_PATH === "string" && (async () => {
-  return (await import("node:fs/promises"))
+/*
+ * Load from file when WASM_BINARY isn't inlined.
+ * A LogicalExpression is used here instead of a ConditionalExpression,
+ * to ensure esbuild perform dead code elimination correctly.
+ */
+const loadWasm = (typeof WASM_BINARY === 'undefined' && (async () => {
+  // we can safely assume import.meta works here with the following workaround.
+  // https://github.com/nodejs/cjs-module-lexer/blob/bcc6ce4/build.js#L36-L53
+  return (await import('node:fs/promises'))
     .readFile(
-      (await import("node:url")).fileURLToPath(
-        import.meta.resolve("../lib/lexer.wasm")
+      (await import('node:url')).fileURLToPath(
+        import.meta.resolve('../lib/lexer.wasm')
       )
   );
 })) || (async () => {
   const binary = WASM_BINARY
-  if (typeof window !== "undefined" && typeof atob === "function") {
+  if (typeof window !== 'undefined' && typeof atob === 'function') {
     return Uint8Array.from(atob(binary), (x) => x.charCodeAt(0));
   } else {
-    return Buffer.from(binary, "base64");
+    return Buffer.from(binary, 'base64');
   }
 });