Windows failing with "expected an absolute Windows path for junction_target"

[mbland]

The bazel-contrib/rules_scala daily CI build began failing on Windows with Bazel 7.7.1 at bazel-contrib/rules_scala@eae29fd:

• Passing: bazel-contrib/rules_scala Windows build from Tue 20th Jan 2026 at 00:00 UTC
• Failing: bazel-contrib/rules_scala Windows build from Wed 21st Jan 2026 at 00:00 UTC

The error is:

ERROR: <builtin>: fetching local_repository rule //:rules_scala+:
  java.io.IOException: Could not create symlink to repository
  "/c/b/bk-windows-8slj/bazel/rules-scala-scala/tmp/test_bzlmod_macros"
  (absolute path: "/c/b/bk-windows-8slj/bazel/rules-scala-scala/tmp/test_bzlmod_macros"):
Cannot create junction
  (name=C:\tools\msys64\home\b\_bazel_b\jto5y4qq\external\rules_scala+,
   target=\c\b\bk-windows-8slj\bazel\rules-scala-scala\tmp\test_bzlmod_macros):
ERROR: src/main/native/windows/file-jni.cc(122):
  nativeCreateJunction(\\?\C:\tools\msys64\home\b\_bazel_b\jto5y4qq\external\rules_scala+,
    \\?\\c\b\bk-windows-8slj\bazel\rules-scala-scala\tmp\test_bzlmod_macros):
ERROR: src/main/native/windows/file.cc(231):
  CreateJunction(\\?\\c\b\bk-windows-8slj\bazel\rules-scala-scala\tmp\test_bzlmod_macros):
expected an absolute Windows path for junction_target

There's nothing from diffing the raw Buildkite logs to suggest that anything changed. Was there a Windows build image change that could account for this? Is there a workaround, or does Bazel itself require a fix, since this happens in the local_repository implementation?

[mbland]

I've managed to resolve this issue for rules_scala in bazel-contrib/rules_scala#1803 by applying cygpath -w to paths used to generate test modules. I'm still curious what might've changed.

[meteorcloudy]

Yes, I did rebuild the windows vm image around the same time. But I didn't make any specific change that related to this.

[meteorcloudy]

I suspect it might the msys version got upgraded and no longer translates your path for some reason.

[meteorcloudy]

I'll close this for now since you have resolved the issue and we don't have any other impacted user so far.