src: fix ESM path resolution on Windows

Windows has some reserved file names such as "con", "prn",
"nul", etc. Such files can be accessed only if the path is
prefixed with "\\.\"

PR-URL: #29574
Reviewed-By: Guy Bedford <[email protected]>

src/module_wrap.cc

@@ -488,7 +488,12 @@ enum DescriptorType {
 // Nothing for the "null" cache entries.
 inline Maybe<uv_file> OpenDescriptor(const std::string& path) {
   uv_fs_t fs_req;
+#ifdef _WIN32
+  std::string pth = "\\\\.\\" + path;
+  uv_file fd = uv_fs_open(nullptr, &fs_req, pth.c_str(), O_RDONLY, 0, nullptr);
+#else
   uv_file fd = uv_fs_open(nullptr, &fs_req, path.c_str(), O_RDONLY, 0, nullptr);
+#endif
   uv_fs_req_cleanup(&fs_req);
   if (fd < 0) return Nothing<uv_file>();
   return Just(fd);

test/es-module/test-esm-windows.js

@@ -0,0 +1,49 @@
+'use strict';
+
+// Flags: --experimental-modules
+// This test ensures that JavaScript file that includes
+// a reserved Windows word can be loaded as ESM module
+
+const common = require('../common');
+const tmpdir = require('../common/tmpdir');
+const assert = require('assert');
+const fs = require('fs').promises;
+const path = require('path');
+
+const imp = (file) => {
+  return import(path.relative(__dirname, file).replace(/\\/g, '/'));
+};
+
+(async () => {
+  const tmp = tmpdir.path;
+  await fs.mkdir(tmp).catch(() => {});
+  const rel = (file) => path.join(tmp, file);
+
+  { // Load a single script
+    const file = rel('con.mjs');
+    await fs.writeFile(file, 'export default "ok"');
+    assert.strictEqual((await imp(file)).default, 'ok');
+    await fs.unlink(file);
+  }
+
+  { // Load a module
+    const entry = rel('entry.mjs');
+    const nmDir = rel('node_modules');
+    const mDir = rel('node_modules/con');
+    const pkg = rel('node_modules/con/package.json');
+    const script = rel('node_modules/con/index.mjs');
+
+    await fs.writeFile(entry, 'export {default} from "con"');
+    await fs.mkdir(nmDir);
+    await fs.mkdir(mDir);
+    await fs.writeFile(pkg, '{"main":"index.mjs"}');
+    await fs.writeFile(script, 'export default "ok"');
+
+    assert.strictEqual((await imp(entry)).default, 'ok');
+    await fs.unlink(script);
+    await fs.unlink(pkg);
+    await fs.rmdir(mDir);
+    await fs.rmdir(nmDir);
+    await fs.unlink(entry);
+  }
+})().then(common.mustCall());