fix(core): preserve output directory separators in mkdir

Keep dirname results unchanged when creating output folders so mixed-separator paths on POSIX resolve to the same parent directory used for writes.

Also update core path-handling tests and add a regression case for mixed separators (tmp\sub/out.js).

Author: srod

packages/core/__tests__/compress-paths.test.ts

@@ -34,13 +34,13 @@ describe("compress path handling", () => {
 
         await compress(settings);
 
-        expect(vi.mocked(mkdir)).toHaveBeenCalledWith("nested/dir", {
+        expect(vi.mocked(mkdir)).toHaveBeenCalledWith("nested\\dir", {
             recursive: true,
         });
         expect(vi.mocked(compressSingleFile)).toHaveBeenCalledTimes(1);
     });
 
-    test("should normalize dirname output before mkdir", async () => {
+    test("should preserve dirname separators before mkdir", async () => {
         vi.spyOn(path, "dirname").mockReturnValue("nested\\dir");
 
         const compressor: Compressor = async () => ({ code: "ok" });
@@ -52,7 +52,23 @@ describe("compress path handling", () => {
 
         await compress(settings);
 
-        expect(vi.mocked(mkdir)).toHaveBeenCalledWith("nested/dir", {
+        expect(vi.mocked(mkdir)).toHaveBeenCalledWith("nested\\dir", {
+            recursive: true,
+        });
+        expect(vi.mocked(compressSingleFile)).toHaveBeenCalledTimes(1);
+    });
+
+    test("should preserve mixed-separator directory paths", async () => {
+        const compressor: Compressor = async () => ({ code: "ok" });
+        const settings: Settings = {
+            compressor,
+            input: "input.js",
+            output: "tmp\\sub/out.js",
+        };
+
+        await compress(settings);
+
+        expect(vi.mocked(mkdir)).toHaveBeenCalledWith("tmp\\sub", {
             recursive: true,
         });
         expect(vi.mocked(compressSingleFile)).toHaveBeenCalledTimes(1);

packages/core/src/compress.ts

@@ -136,12 +136,12 @@ async function createDirectory(filePath: string | string[]) {
 function getDirectoryPath(outputPath: string): string {
     const dirPath = path.dirname(outputPath);
     if (dirPath && dirPath !== ".") {
-        return dirPath.replaceAll("\\", "/");
+        return dirPath;
     }
 
     const windowsDirPath = path.win32.dirname(outputPath);
     if (windowsDirPath && windowsDirPath !== ".") {
-        return windowsDirPath.replaceAll("\\", "/");
+        return windowsDirPath;
     }
 
     return "";