esm: use wasm version of cjs-module-lexer

benchmark/esm/import-cjs.js

@@ -0,0 +1,41 @@
+'use strict';
+const common = require('../common.js');
+const assert = require('assert');
+const tmpdir = require('../../test/common/tmpdir');
+const fixtures = require('../../test/common/fixtures.js');
+const fs = require('fs');
+
+// This fixture has 2000+ exports.
+const fixtureFile = fixtures.path('snapshot', 'typescript.js');
+// This is fixed - typescript.js is slow to load, so 10 is enough.
+// And we want to measure either 10 warm loads, or 1 cold load (but compare.js would run it many times)
+const runs = 10;
+const bench = common.createBenchmark(main, {
+  type: ['cold', 'warm'],
+}, {
+  setup() {
+    tmpdir.refresh();
+    fs.cpSync(fixtureFile, tmpdir.resolve(`imported-cjs-initial.js`));
+    for (let i = 0; i < runs; i++) {
+      fs.cpSync(fixtureFile, tmpdir.resolve(`imported-cjs-${i}.js`));
+    }
+  },
+});
+
+async function main({ type }) {
+  if (type === 'cold') {
+    bench.start();
+    await import(tmpdir.fileURL(`imported-cjs-initial.js`));
+    bench.end(1);
+  } else {
+    await import(tmpdir.fileURL(`imported-cjs-initial.js`));  // Initialize the wasm first.
+    bench.start();
+    let result;
+    for (let i = 0; i < runs; i++) {
+      result = await import(tmpdir.fileURL(`imported-cjs-${i}.js`));
+    }
+    bench.end(runs);
+    const mod = require(fixtures.path('snapshot', 'typescript.js'));
+    assert.deepStrictEqual(Object.keys(mod), Object.keys(result.default));
+  }
+}

lib/internal/modules/esm/translators.js

@@ -74,12 +74,17 @@ function getSource(url) {
 let cjsParse;
 /**
  * Initializes the CommonJS module lexer parser using the JavaScript version.
- * TODO(joyeecheung): Use `require('internal/deps/cjs-module-lexer/dist/lexer').initSync()`
- * when cjs-module-lexer 1.4.0 is rolled in.
  */
 function initCJSParseSync() {
   if (cjsParse === undefined) {
-    cjsParse = require('internal/deps/cjs-module-lexer/lexer').parse;
+    if (typeof WebAssembly !== 'undefined') {
+      const { parse, initSync } = require('internal/deps/cjs-module-lexer/dist/lexer');
+      initSync();
+      cjsParse = parse;
+    } else {
+      const { parse } = require('internal/deps/cjs-module-lexer/lexer');
+      cjsParse = parse;
+    }
   }
 }
 

test/es-module/test-import-cjs-jitless.mjs

@@ -0,0 +1,6 @@
+// Flags: --jitless
+
+// Tests that importing a CJS module works in JIT-less mode (i.e. falling back to the
+// JS parser if WASM is not available).
+import '../common/index.mjs';
+import '../fixtures/empty.cjs';