feat: add Windows support by handling empty path case in PathSplit function

[pcanilho]

Goal: Fix PathSplit function to handle empty path case for Windows support

Context: This PR fixes an issue I was having when adding Windows support for some of my utilities by updating the function to handle the case when is empty.

The issue

When running on Windows, I was getting errors because the function wasn't handling empty paths correctly. The problem occurs because Windows uses backslashes (\) as path separators, so when resolves to \, the path splitting logic behaves differently than on Unix systems.
For example, I was seeing errors like this locally:

C:\Users\<user>\AppData\Local\Temp\<my_local_git>@<local_ref>

Causing a stack overflow:

click here to see the stack trace... ❗️

fatal error: stack overflow

runtime stack:
runtime.throw({0x7ff62c817a83?, 0x7ff62a2ef630?})
        C:/Program Files/Go/src/runtime/panic.go:1101 +0x38 fp=0x26bffffd60 sp=0x26bffffd30 pc=0x7ff62a331418
runtime.newstack()
        C:/Program Files/Go/src/runtime/stack.go:1107 +0x464 fp=0x26bffffea0 sp=0x26bffffd60 pc=0x7ff62a318094
runtime.morestack()
        C:/Program Files/Go/src/runtime/asm_arm64.s:342 +0x70 fp=0x26bffffea0 sp=0x26bffffea0 pc=0x7ff62a336d60

goroutine 52 gp=0x400072a700 m=10 mp=0x4000742008 [running]:
internal/filepathlite.1({0x40020ea7b0, 0x7})
        C:/Program Files/Go/src/internal/filepathlite/path_windows.go:204 +0x2b8 fp=0x4022d67380 sp=0x4022d67380 pc=0x7ff62a382af8
internal/filepathlite.VolumeName({0x40020ea7b0, 0x7})
        C:/Program Files/Go/src/internal/filepathlite/path.go:267 +0x24 fp=0x4022d673b0 sp=0x4022d67380 pc=0x7ff62a381e24
internal/filepathlite.Split({0x40020ea7b0, 0x7})
        C:/Program Files/Go/src/internal/filepathlite/path.go:206 +0x24 fp=0x4022d673d0 sp=0x4022d673b0 pc=0x7ff62a381b04
path/filepath.Split(...)
        C:/Program Files/Go/src/path/filepath/path.go:120
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:44 +0x28 fp=0x4022d67450 sp=0x4022d673d0 pc=0x7ff62b8c2968
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d674d0 sp=0x4022d67450 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d67550 sp=0x4022d674d0 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d675d0 sp=0x4022d67550 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d67650 sp=0x4022d675d0 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d676d0 sp=0x4022d67650 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d67750 sp=0x4022d676d0 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d677d0 sp=0x4022d67750 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d67850 sp=0x4022d677d0 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
        C:/Users/my_user/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/filesys/util.go:55 +0x168 fp=0x4022d678d0 sp=0x4022d67850 pc=0x7ff62b8c2aa8
sigs.k8s.io/kustomize/kyaml/filesys.PathSplit({0x40020ea7b0?, 0x7?})
...

Note: go version go1.24.5 windows/arm64

My proposal

I added a simple check to the existing condition in . This prevents issues when working with Windows systems.

@@ -49,7 +49,7 @@ func PathSplit(incoming string) []string {
                return []string{"", path}
        }
        dir = strings.TrimSuffix(dir, string(os.PathSeparator))
-       if dir == "" {
+       if dir == "" || path == "" {
                return []string{path}
        }
        return append(PathSplit(dir), path)

Why this works

The existing tests already pass with this change, which confirms this change does not impact existing unix support. It is aimed at ensuring consistent behaviour across operating systems without requiring more invasive changes.

Testing notes

The existing tests exclude Windows intentionally, and I wasn't sure if adapting them would be straightforward since proper testing needs to be done on a Windows host where resolves to the Windows-specific rune.

Any form of feedback is greatly appreciated.

[linux-foundation-easycla]

• ✅login: pcanilho / (825b1cc)

The committers listed above are authorized under a signed CLA.

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[koba1t]

Hi @pcanilho

Thanks for open PR.
Please add tests that reproduce the issue this PR fixes, following the guide below.

https://github.com/kubernetes-sigs/kustomize/blob/master/CONTRIBUTING.md#reviewer-guide

• The PR should have two distinct commits:
  • The first commit should add a test demonstrating incorrect behavior
  • The second commit should include the bug fix
  • Some sample PRs:
    • https://github.com/kubernetes-sigs/kustomize/pull/5263/commits
    • https://github.com/kubernetes-sigs/kustomize/pull/3931/commits
  • The regression test is absolutely required, and we cannot accept bug fixes without tests.

[pcanilho]

Sorry I missed your message, @koba1t!

Regarding the test coverage: I noticed the existing test suite for this functionality intentionally excludes Windows (https://github.com/kubernetes-sigs/kustomize/blob/master/kyaml/filesys/util_test.go#L4-L5).

Would you prefer that I adapt those tests to be cross-platform compatible, or should I create a separate Windows-specific test suite instead? I'm happy to take either approach and just want to follow the project's preferred testing pattern.

[koba1t]

@pcanilho

I think the test cases in kyaml/filesys/util_test.go depend on POSIX-style path notation.
I prefer to add something like util_test_windows.go.