tests/opa: normalize path separators in folder filter on Windows

[kusha]

Summary

On Windows, cargo xtask pre-push fails immediately at the OPA testsuite stage with Error: no matching tests found., even though the testsuite is present and every other check passes. The cause is a path-separator mismatch in the folder filter in tests/opa.rs.

Root cause

run_opa_tests builds path_dir_str from Path::to_string_lossy(), which on Windows yields backslash separators (e.g. v0\aggregates). The folder filter then does an exact-string comparison against the CLI arguments:

let path_dir_str = path_dir.to_string_lossy().to_string();
// ...
let run_test = folders.is_empty()
    || folders.iter().any(|f| &path_dir_str == f);

CLI arguments — including the ones the cargo xtask pre-push hook passes — use forward slashes (v0/aggregates). On Windows the equality check never matches, no folders are selected, npass == 0 && nfail == 0, and the function bails. The neighboring is_rego_v0_test check already accounts for the separator difference (starts_with("v0/") || path_dir.starts_with("v0\\")), but the filter comparison was missed.

Reproduction

On Windows, against main at 11940dd:

cargo test --features opa-testutil,serde_json/arbitrary_precision,rego-extensions \
  --test opa -- v1/aggregates

Output:

OPA TESTSUITE STATUS
    FOLDER                                    PASS FAIL

Error: no matching tests found.

Exit code 1. The same failure blocks cargo xtask pre-push for any change on this platform.

Fix

Normalize path_dir_str to forward slashes at construction time:

-        let path_dir_str = path_dir.to_string_lossy().to_string();
+        // Normalize to forward slashes so the folder filter at the
+        // `folders.iter().any(|f| &path_dir_str == f)` check below matches
+        // CLI arguments like `v0/aggregates` on Windows, where
+        // `to_string_lossy` yields backslash separators by default.
+        let path_dir_str = path_dir.to_string_lossy().replace('\\', "/");

Single line of logic. No behavior change on Unix-like platforms (no backslashes to replace).

Validation

After the fix, on the same Windows machine:

Command	Before	After
cargo test ... --test opa -- v1/aggregates	exit 1, no matching tests found	exit 0, 72 / 0
cargo test ... --test opa -- <all 188 v0/* and v1/* folders> (the pre-push hook command)	exit 1, no matching tests found	exit 0, TOTAL: 2861 / 0
cargo xtask pre-commit	passes	passes (unaffected)

Notes

• The duplicate platform branch at path_dir.starts_with("v0\\") becomes redundant after this change but is left intact to keep the diff minimal — happy to remove it in a follow-up if preferred.
• This is a test-only change; no library or RVM code is touched.

[Copilot]

Pull request overview

Fixes Windows-only failures in the OPA conformance test runner by normalizing directory paths used for folder filtering so they match the forward-slash format passed via CLI (and the tests/opa.passing list), preventing the “no matching tests found” early exit.

Changes:

• Normalize path_dir_str to use / separators when deriving folder names in run_opa_tests.
• Add an explanatory comment documenting the Windows path-separator mismatch and why normalization is needed.