Resolve #17271 staticDirs path issue on Windows

lib/core-server/src/utils/__tests__/server-statics.test.ts

@@ -72,6 +72,13 @@ describe('parseStaticDir', () => {
       targetDir: './custom-endpoint',
       targetEndpoint: '/custom-endpoint',
     });
+
+    await expect(parseStaticDir('C:\\foo\\bar:\\custom-endpoint')).resolves.toEqual({
+      staticDir: expect.any(String), // can't test this properly on unix
+      staticPath: path.resolve('C:\\foo\\bar'),
+      targetDir: './custom-endpoint',
+      targetEndpoint: '/custom-endpoint',
+    });
   });
 
   it('pins relative endpoint at root', async () => {

lib/core-server/src/utils/server-statics.ts

@@ -66,12 +66,20 @@ export async function useStatics(router: any, options: Options) {
 }
 
 export const parseStaticDir = async (arg: string) => {
-  // Split on ':' only if not followed by '\', for Windows compatibility (e.g. 'C:\some\dir')
-  const [rawDir, target = '/'] = arg.split(/:(?!\\)/);
+  // Split on last index of ':', for Windows compatibility (e.g. 'C:\some\dir:\foo')
+  const lastColonIndex = arg.lastIndexOf(':');
+  const isWindowsAbsolute = path.win32.isAbsolute(arg);
+  const isWindowsRawDirOnly = isWindowsAbsolute && lastColonIndex === 1; // e.g. 'C:\some\dir'
+  const splitIndex = lastColonIndex !== -1 && !isWindowsRawDirOnly ? lastColonIndex : arg.length;
+
+  const targetRaw = arg.substring(splitIndex + 1) || '/';
+  const target = targetRaw.split(path.sep).join(path.posix.sep); // Ensure target has forward-slash path
+
+  const rawDir = arg.substring(0, splitIndex);
   const staticDir = path.isAbsolute(rawDir) ? rawDir : `./${rawDir}`;
   const staticPath = path.resolve(staticDir);
   const targetDir = target.replace(/^\/?/, './');
-  const targetEndpoint = targetDir.substr(1);
+  const targetEndpoint = targetDir.substring(1);
 
   if (!(await pathExists(staticPath))) {
     throw new Error(