module: fix EISDIR error with Windows drive-letter-only paths

lib/_http_outgoing.js

@@ -287,14 +287,20 @@ OutgoingMessage.prototype.uncork = function uncork() {
       callbacks.push(buf[n + 2]);
     }
   }
-  this._send(crlf_buf, null, callbacks.length ? (err) => {
+  const ret = this._send(crlf_buf, null, callbacks.length ? (err) => {
     for (const callback of callbacks) {
       callback(err);
     }
   } : null);
 
   this[kChunkedBuffer].length = 0;
   this[kChunkedLength] = 0;
+
+  // If we successfully flushed and had pending drain, emit it
+  if (ret && this[kNeedDrain]) {
+    this[kNeedDrain] = false;
+    this.emit('drain');
+  }
 };
 
 OutgoingMessage.prototype.setTimeout = function setTimeout(msecs, callback) {

lib/internal/modules/helpers.js

@@ -59,6 +59,12 @@ const realpathCache = new SafeMap();
  * @returns {string}
  */
 function toRealPath(requestPath) {
+  // On Windows, ensure the path is valid before calling realpathSync
+  // to avoid EISDIR errors with malformed paths like 'C:' (drive letter only)
+  if (process.platform === 'win32' && requestPath.length === 2 && requestPath[1] === ':') {
+    // If we have just a drive letter, add trailing backslash to make it valid
+    requestPath += '\\';
+  }
   return fs.realpathSync(requestPath, {
     [internalFS.realpathCacheKey]: realpathCache,
   });