esm: fix extensionless import for --type

lib/internal/modules/esm/default_resolve.js

@@ -75,15 +75,15 @@ function resolve(specifier, parentURL) {
  }
  }
  }
-
  if (!format) {
- if (isMain)
+ if (isMain && asyncESM.typeFlag)
+ format = asyncESM.typeFlag;
+ else if (isMain)
  format = type === 2 ? 'module' : 'commonjs';
  else
  throw new ERR_UNKNOWN_FILE_EXTENSION(fileURLToPath(url),
  fileURLToPath(parentURL));
  }
-
  return { url: `${url}`, format };
 }
 

test/es-module/test-esm-no-extension.js

@@ -0,0 +1,32 @@
+'use strict';
+
+const common = require('../common');
+const fixtures = require('../common/fixtures');
+const { spawn } = require('child_process');
+const assert = require('assert');
+
+const entry = fixtures.path('/es-modules/noext-esm');
+
+const child = spawn(process.execPath, [
+ '--experimental-modules',
+ '--type=module',
+ entry
+]);
+
+let stderr = '';
+child.stderr.setEncoding('utf8');
+child.stderr.on('data', (data) => {
+ stderr += data;
+});
+let stdout = '';
+child.stdout.setEncoding('utf8');
+child.stdout.on('data', (data) => {
+ stdout += data;
+});
+child.on('close', common.mustCall((code, signal) => {
+ assert.strictEqual(code, 0);
+ assert.strictEqual(signal, null);
+ assert.strictEqual(stdout, 'executed\n');
+ assert.strictEqual(stderr, `(node:${child.pid}) ` +
+ 'ExperimentalWarning: The ESM module loader is experimental.\n');
+}));

test/fixtures/es-modules/noext-esm

@@ -0,0 +1,2 @@
+export default 'module';
+console.log('executed');