esm: unflag extensionless javascript and wasm in module scope

PR-URL: #49974
Backport-PR-URL: #50669
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

doc/api/esm.md

@@ -1008,8 +1008,12 @@ _isImports_, _conditions_)
 > 5. Let _packageURL_ be the result of **LOOKUP\_PACKAGE\_SCOPE**(_url_).
 > 6. Let _pjson_ be the result of **READ\_PACKAGE\_JSON**(_packageURL_).
 > 7. If _pjson?.type_ exists and is _"module"_, then
->    1. If _url_ ends in _".js"_, then
->       1. Return _"module"_.
+>    1. If _url_ ends in _".js"_ or has no file extension, then
+>       1. If `--experimental-wasm-modules` is enabled and the file at _url_
+>          contains the header for a WebAssembly module, then
+>          1. Return _"wasm"_.
+>       2. Otherwise,
+>          1. Return _"module"_.
 >    2. Return **undefined**.
 > 8. Otherwise,
 >    1. Return **undefined**.

lib/internal/errors.js

@@ -1686,13 +1686,7 @@ E('ERR_UNHANDLED_ERROR',
 E('ERR_UNKNOWN_BUILTIN_MODULE', 'No such built-in module: %s', Error);
 E('ERR_UNKNOWN_CREDENTIAL', '%s identifier does not exist: %s', Error);
 E('ERR_UNKNOWN_ENCODING', 'Unknown encoding: %s', TypeError);
-E('ERR_UNKNOWN_FILE_EXTENSION', (ext, path, suggestion) => {
-  let msg = `Unknown file extension "${ext}" for ${path}`;
-  if (suggestion) {
-    msg += `. ${suggestion}`;
-  }
-  return msg;
-}, TypeError);
+E('ERR_UNKNOWN_FILE_EXTENSION', 'Unknown file extension "%s" for %s', TypeError);
 E('ERR_UNKNOWN_MODULE_FORMAT', 'Unknown module format: %s for URL %s',
   RangeError);
 E('ERR_UNKNOWN_SIGNAL', 'Unknown signal: %s', TypeError);

lib/internal/modules/esm/get_format.js

@@ -9,7 +9,6 @@ const {
   StringPrototypeCharCodeAt,
   StringPrototypeSlice,
 } = primordials;
-const { basename, relative } = require('path');
 const { getOptionValue } = require('internal/options');
 const {
   extensionFormatMap,
@@ -25,7 +24,7 @@ const experimentalSpecifierResolution =
 const defaultTypeFlag = getOptionValue('--experimental-default-type');
 // The next line is where we flip the default to ES modules someday.
 const defaultType = defaultTypeFlag === 'module' ? 'module' : 'commonjs';
-const { getPackageType, getPackageScopeConfig } = require('internal/modules/esm/resolve');
+const { getPackageType } = require('internal/modules/esm/resolve');
 const { fileURLToPath } = require('internal/url');
 const { ERR_UNKNOWN_FILE_EXTENSION } = require('internal/errors').codes;
 
@@ -115,17 +114,16 @@ function getFileProtocolModuleFormat(url, context, ignoreErrors) {
     if (defaultType === 'commonjs') { // Legacy behavior
       if (packageType === 'none' || packageType === 'commonjs') {
         return 'commonjs';
-      }
-      // If package type is `module`, fall through to the error case below
-    } else { // Else defaultType === 'module'
-      if (underNodeModules(url)) { // Exception for package scopes under `node_modules`
-        return 'commonjs';
-      }
-      if (packageType === 'none' || packageType === 'module') {
-        return getFormatOfExtensionlessFile(url);
-      } // Else packageType === 'commonjs'
-      return 'commonjs';
+      } // Else packageType === 'module'
+      return getFormatOfExtensionlessFile(url);
+    } // Else defaultType === 'module'
+    if (underNodeModules(url)) { // Exception for package scopes under `node_modules`
+      return packageType === 'module' ? getFormatOfExtensionlessFile(url) : 'commonjs';
     }
+    if (packageType === 'none' || packageType === 'module') {
+      return getFormatOfExtensionlessFile(url);
+    } // Else packageType === 'commonjs'
+    return 'commonjs';
   }
 
   const format = extensionFormatMap[ext];
@@ -135,17 +133,7 @@ function getFileProtocolModuleFormat(url, context, ignoreErrors) {
     // Explicit undefined return indicates load hook should rerun format check
     if (ignoreErrors) { return undefined; }
     const filepath = fileURLToPath(url);
-    let suggestion = '';
-    if (getPackageType(url) === 'module' && ext === '') {
-      const config = getPackageScopeConfig(url);
-      const fileBasename = basename(filepath);
-      const relativePath = StringPrototypeSlice(relative(config.pjsonPath, filepath), 1);
-      suggestion = 'Loading extensionless files is not supported inside of "type":"module" package.json contexts ' +
-        `without --experimental-default-type=module. The package.json file ${config.pjsonPath} caused this "type":"module" ` +
-        `context. Try changing ${filepath} to have a file extension. Note the "bin" field of package.json can point ` +
-        `to a file with an extension, for example {"type":"module","bin":{"${fileBasename}":"${relativePath}.js"}}`;
-    }
-    throw new ERR_UNKNOWN_FILE_EXTENSION(ext, filepath, suggestion);
+    throw new ERR_UNKNOWN_FILE_EXTENSION(ext, filepath);
   }
 
   return getLegacyExtensionFormat(ext) ?? null;

test/es-module/test-esm-extensionless-esm-and-wasm.mjs

@@ -0,0 +1,106 @@
+// Flags: --experimental-wasm-modules
+import { mustNotCall, spawnPromisified } from '../common/index.mjs';
+import * as fixtures from '../common/fixtures.mjs';
+import { describe, it } from 'node:test';
+import { match, ok, strictEqual } from 'node:assert';
+
+describe('extensionless ES modules within a "type": "module" package scope', { concurrency: true }, () => {
+  it('should run as the entry point', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [
+      fixtures.path('es-modules/package-type-module/noext-esm'),
+    ]);
+
+    strictEqual(stderr, '');
+    strictEqual(stdout, 'executed\n');
+    strictEqual(code, 0);
+    strictEqual(signal, null);
+  });
+
+  it('should be importable', async () => {
+    const { default: defaultExport } =
+              await import(fixtures.fileURL('es-modules/package-type-module/noext-esm'));
+    strictEqual(defaultExport, 'module');
+  });
+
+  it('should be importable from a module scope under node_modules', async () => {
+    const { default: defaultExport } =
+      await import(fixtures.fileURL(
+        'es-modules/package-type-module/node_modules/dep-with-package-json-type-module/noext-esm'));
+    strictEqual(defaultExport, 'module');
+  });
+});
+describe('extensionless Wasm modules within a "type": "module" package scope', { concurrency: true }, () => {
+  it('should run as the entry point', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [
+      '--experimental-wasm-modules',
+      '--no-warnings',
+      fixtures.path('es-modules/package-type-module/noext-wasm'),
+    ]);
+
+    strictEqual(stderr, '');
+    strictEqual(stdout, 'executed\n');
+    strictEqual(code, 0);
+    strictEqual(signal, null);
+  });
+
+  it('should be importable', async () => {
+    const { add } = await import(fixtures.fileURL('es-modules/package-type-module/noext-wasm'));
+    strictEqual(add(1, 2), 3);
+  });
+
+  it('should be importable from a module scope under node_modules', async () => {
+    const { add } = await import(fixtures.fileURL(
+      'es-modules/package-type-module/node_modules/dep-with-package-json-type-module/noext-wasm'));
+    strictEqual(add(1, 2), 3);
+  });
+});
+
+describe('extensionless ES modules within no package scope', { concurrency: true }, () => {
+  // This succeeds with `--experimental-default-type=module`
+  it('should error as the entry point', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [
+      fixtures.path('es-modules/noext-esm'),
+    ]);
+
+    match(stderr, /SyntaxError/);
+    strictEqual(stdout, '');
+    strictEqual(code, 1);
+    strictEqual(signal, null);
+  });
+
+  // This succeeds with `--experimental-default-type=module`
+  it('should error on import', async () => {
+    try {
+      await import(fixtures.fileURL('es-modules/noext-esm'));
+      mustNotCall();
+    } catch (err) {
+      ok(err instanceof SyntaxError);
+    }
+  });
+});
+
+describe('extensionless Wasm within no package scope', { concurrency: true }, () => {
+  // This succeeds with `--experimental-default-type=module`
+  it('should error as the entry point', async () => {
+    const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [
+      '--experimental-wasm-modules',
+      '--no-warnings',
+      fixtures.path('es-modules/noext-wasm'),
+    ]);
+
+    match(stderr, /SyntaxError/);
+    strictEqual(stdout, '');
+    strictEqual(code, 1);
+    strictEqual(signal, null);
+  });
+
+  // This succeeds with `--experimental-default-type=module`
+  it('should error on import', async () => {
+    try {
+      await import(fixtures.fileURL('es-modules/noext-wasm'));
+      mustNotCall();
+    } catch (err) {
+      ok(err instanceof SyntaxError);
+    }
+  });
+});

test/es-module/test-esm-type-flag-package-scopes.mjs

@@ -24,6 +24,14 @@ describe('the type flag should change the interpretation of certain files within
              strictEqual(defaultExport, 'module');
            });
 
+           it('should import an extensionless JavaScript file within a "type": "module" scope under node_modules',
+              async () => {
+                const { default: defaultExport } =
+                await import(fixtures.fileURL(
+                  'es-modules/package-type-module/node_modules/dep-with-package-json-type-module/noext-esm'));
+                strictEqual(defaultExport, 'module');
+              });
+
            it('should run as Wasm an extensionless Wasm file within a "type": "module" scope', async () => {
              const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [
                '--experimental-default-type=module',
@@ -42,6 +50,13 @@ describe('the type flag should change the interpretation of certain files within
              const { add } = await import(fixtures.fileURL('es-modules/package-type-module/noext-wasm'));
              strictEqual(add(1, 2), 3);
            });
+
+           it('should import an extensionless Wasm file within a "type": "module" scope under node_modules',
+              async () => {
+                const { add } = await import(fixtures.fileURL(
+                  'es-modules/package-type-module/node_modules/dep-with-package-json-type-module/noext-wasm'));
+                strictEqual(add(1, 2), 3);
+              });
          });
 
 describe(`the type flag should change the interpretation of certain files within a package scope that lacks a
@@ -112,7 +127,7 @@ describe(`the type flag should NOT change the interpretation of certain files wi
      async () => {
        const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [
          '--experimental-default-type=module',
-         fixtures.path('es-modules/package-type-module/node_modules/dep-with-package-json/run.js'),
+         fixtures.path('es-modules/package-type-module/node_modules/dep-with-package-json-without-type/run.js'),
        ]);
 
        strictEqual(stderr, '');
@@ -124,15 +139,16 @@ describe(`the type flag should NOT change the interpretation of certain files wi
   it(`should import as CommonJS a .js file within a package scope that has no defined "type" and is under
   node_modules`, async () => {
     const { default: defaultExport } =
-      await import(fixtures.fileURL('es-modules/package-type-module/node_modules/dep-with-package-json/run.js'));
+      await import(fixtures.fileURL(
+        'es-modules/package-type-module/node_modules/dep-with-package-json-without-type/run.js'));
     strictEqual(defaultExport, 42);
   });
 
   it(`should run as CommonJS an extensionless JavaScript file within a package scope that has no defined "type" and is
   under node_modules`, async () => {
     const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [
       '--experimental-default-type=module',
-      fixtures.path('es-modules/package-type-module/node_modules/dep-with-package-json/noext-cjs'),
+      fixtures.path('es-modules/package-type-module/node_modules/dep-with-package-json-without-type/noext-cjs'),
     ]);
 
     strictEqual(stderr, '');
@@ -144,7 +160,8 @@ describe(`the type flag should NOT change the interpretation of certain files wi
   it(`should import as CommonJS an extensionless JavaScript file within a package scope that has no defined "type" and
   is under node_modules`, async () => {
     const { default: defaultExport } =
-      await import(fixtures.fileURL('es-modules/package-type-module/node_modules/dep-with-package-json/noext-cjs'));
+      await import(fixtures.fileURL(
+        'es-modules/package-type-module/node_modules/dep-with-package-json-without-type/noext-cjs'));
     strictEqual(defaultExport, 42);
   });
 });

test/es-module/test-esm-unknown-or-no-extension.js → test/es-module/test-esm-unknown-extension.js

@@ -7,14 +7,11 @@ const { execPath } = require('node:process');
 const { describe, it } = require('node:test');
 
 
-// In a "type": "module" package scope, files with unknown extensions or no
-// extensions should throw; both when used as a main entry point and also when
-// referenced via `import`.
-describe('ESM: extensionless and unknown specifiers', { concurrency: true }, () => {
+// In a "type": "module" package scope, files with unknown extensions should throw;
+// both when used as a main entry point and also when referenced via `import`.
+describe('ESM: unknown specifiers', { concurrency: true }, () => {
   for (
     const fixturePath of [
-      '/es-modules/package-type-module/noext-esm',
-      '/es-modules/package-type-module/imports-noext.mjs',
       '/es-modules/package-type-module/extension.unknown',
       '/es-modules/package-type-module/imports-unknownext.mjs',
     ]
@@ -27,10 +24,6 @@ describe('ESM: extensionless and unknown specifiers', { concurrency: true }, ()
       assert.strictEqual(signal, null);
       assert.strictEqual(stdout, '');
       assert.match(stderr, /ERR_UNKNOWN_FILE_EXTENSION/);
-      if (fixturePath.includes('noext')) {
-        // Check for explanation to users
-        assert.match(stderr, /extensionless/);
-      }
     });
   }
 });