os.FilePath is not working correctly with relative path with scala native

[stephenamar-db]

I'm currently working on debugging databricks/sjsonnet#374 and I think I stumbled upon an issue with scala native.

os.FilePath is not correctly resolving relative paths in scala native.

I tested with scala 2.12.X, 2.13.X and 3.3.X
Library version is com.lihaoyi::os-lib::0.11.4
Scala native version is 0.5.7

~/sjsonnet % uname -a                                                                                                                                           
Darwin QWYD2XFYYF 24.4.0 Darwin Kernel Version 24.4.0: Fri Apr 11 18:33:39 PDT 2025; root:xnu-11417.101.15~117/RELEASE_ARM64_T6020 arm64 arm Darwin

Test case:

import utest.{TestSuite, Tests, test}

object OsPathTest extends TestSuite {
  def tests: Tests = Tests {
    test("os.FilePath") - {
      assert(os.FilePath("../../bar.jsonnet").isInstanceOf[os.RelPath])
    }
  }
}

Scala Native:

~/sjsonnet % ./mill show "sjsonnet.native[3.3.6].test" "sjsonnet.OsPathTest"
[1/1] show
[1-143/150] sjsonnet.native[3.3.6].test.compile
[1-143] [info] compiling 27 Scala sources to /Users/stephen.amar/sjsonnet/out/sjsonnet/native/3.3.6/test/compile.dest/classes ...
[1-143] [info] done compiling
[1-150/150] sjsonnet.native[3.3.6].test.test
[1-150] [info] Starting process '/Users/stephen.amar/sjsonnet/out/sjsonnet/native/3.3.6/test/nativeLink.dest/out' on port '52359'.
---------------------- Running Tests sjsonnet.OsPathTest ----------------------
X sjsonnet.OsPathTest.os.FilePath 3ms
  java.lang.AssertionError: assertion failed
    scala.runtime.Scala3RunTime$.assertFailed(Unknown)
    sjsonnet.OsPathTest$.tests$$anonfun$1$$anonfun$1(Unknown)
[1-150] Test result: 1 completed, 1 failures.
[1-150] Tests: 1, Passed: 0, Failed: 1
[1/1, 1 failed] ============================== show sjsonnet.native[3.3.6].test sjsonnet.OsPathTest ============================== 8s
1 tasks failed
show 1 tasks failed
sjsonnet.native[3.3.6].test.test 1 tests failed:
  sjsonnet.OsPathTest sjsonnet.OsPathTest.os.FilePath

Scala JVM:

14s ~/sjsonnet % ./mill show "sjsonnet.jvm[3.3.6].test" "sjsonnet.OsPathTest"                                                                                   (master +!?)
[1/1] show
[1-108/115] sjsonnet.jvm[3.3.6].test.compile
[1-108] [info] compiling 1 Scala source to /Users/stephen.amar/sjsonnet/out/sjsonnet/jvm/3.3.6/test/compile.dest/classes ...
[1-108] [info] done compiling
[1-115/115] sjsonnet.jvm[3.3.6].test.test
[1-115] ---------------------- Running Tests sjsonnet.OsPathTest ----------------------
[1-115] + sjsonnet.OsPathTest.os.FilePath 11ms
[1-115] Tests: 1, Passed: 1, Failed: 0
[
  "Tests: 1, Passed: 1, Failed: 0",
  [
    {
      "fullyQualifiedName": "sjsonnet.OsPathTest",
      "selector": "sjsonnet.OsPathTest.os.FilePath",
      "duration": 11,
      "status": "Success"
    }
  ]
]
[1/1] ============================== show sjsonnet.jvm[3.3.6].test sjsonnet.OsPathTest ============================== 1s

[He-Pin]

I think we should add a normalize method to the os.Path

[lihaoyi]

os-lib is a pretty thin wrapper around java.nio.file, probably one of underlying methods we are calling is behaving incompatibly on scala-native

[stephenamar-db]

The problem seems to be with Path.normalize() behaving differently in scala native.

JVM: Paths.get("../../bar.jsonnet").normalize() => "../../bar.jsonnet"
Native: Paths.get("../../bar.jsonnet").normalize() => bar.jsonnet

[He-Pin]

@stephenamar-db I think we should report a bug in https://github.com/scala-native/scala-native/issues

[LeeTibbert]

@stephenamar-db

Thank you for reporting this and for the clear reproducer. Using that reproducer, I have replicated the defect
in Scala Native and am working on a Unix fix. Windows may take longer.

[LeeTibbert]

I believe this is fixed in Scala Native 0.5.8.

See the discussion in os-lib PR #394, especially the bottom most entry.
I believe that, with one tiny test edit, os-lib should build with SN 0.5.8
and pass tests. It did for me two or so weeks ago.

I've spent the last two weeks working on a fix to SN Files.copy() so that
even that tiny edit should not be necessary. I currently have a proposed fix
working and am writing extensive unit-tests before SN PR submission.

Of course, that would only be available to os-lib in/after SN 0.5.9.

Of course, if you see anything different than what I describe, please call out
and I will take a look at it. It would be nice to get os-lib working with
a current Scala Native.

Later: I should be clear that the fix in 0.5.8 is known to work on Unix-like (Ubuntu, macOS),
I am not sure if it works for Windows.

[lihaoyi]

Thanks @LeeTibbert !