[PATCH v2 0/3] rust: kunit: support #[should_panic] and same test name with different #[cfg(...)]

[Nicolás Antinori via B4 Relay]

This patch series intends to implement two features for KUnit tests
written in Rust. The work is based on a TODO comment made in the
`bitmap.rs` module [1].

Changelog:

v2: 
- Added more tests in `rust/kernel/kunit.rs` testing Sashiko findings
  and changes.
- Solved Sashiko: "[Low] kunit: spurious "try faulted" error logs for
  successful #[should_panic] tests": Solved by adding
  `rust_should_panic` in `kunit_try_catch` C struct to check if the test
  is expected to panic and act accordingly. Dismissed what I first talked
  about in [3].
- Solved Sashiko: "[Medium] kunit: assert! macro in #[should_panic]
  tests causes unexpected failure": Solved by making `kunit_assert`
  macro aware if the test should panic and act accordingly. Dismissed what
  I first talked about in [3]
- Solved Sashiko: "[Low] kunit: missing diagnostic log for
  #[should_panic] tests that fail to panic": Added an error message when
  a test that was expected to panic do not
- Solved Sashiko: "[Low] kunit: dead_code error for test wrappers with
  inactive cfg": Solved by moving the #[cfg(..)] attributes on top of
  the wrapper functions
- Dismissed Sashiko: "[Medium] rust: bitmap: memory leak in
  owned_bitmap_out_of_bounds() test panic": Not sure if can be done
  anything. If I am not mistaken this is the same issue as stated here [4].

Sashiko report links: https://sashiko.dev/#/patchset/20260930-rust_kunit_v4-v1-0-e3b0d45311dd@xxxxxxxxx?part=1

v1:
- Removed 'stringification' of test names (to avoid clash of names for
  different configurations now a number is appended).
- Added bool `rust_should_panic` attribute to `kunit_attributes` C
  struct
- Removed #[panic_handler] in Rust side, checking for aborts in the C
  side (`kunit_run_case_catch_errors` function). This allow to catch
  panics triggered, for example in a Rust function that called a panicking
  C function.
- Now the tests that have an inactive #[cfg(..)] do not appear un the
  KUnit execution summary as ignored, they just do not run.
Link to v1: https://lore.kernel.org/all/20260930-rust_kunit_v4-v1-0-e3b0d45311dd@xxxxxxxxx/

- RFC patch: https://lore.kernel.org/rust-for-linux/cover.1789500084.git.nico.antinori.7@xxxxxxxxx/

1. Supporting `#[should_panic]` [2]:

KUnit tests in Rust follow the user-space syntax, but at the moment
`#[should_panic]` is not supported. The first patch of this series adds
support for the attribute (only in its basic form, `#[should_panic =
"message"]` is not supported yet).

The way it is supported is by adding a new boolean property called
`rust_should_panic` to `kunit_attributes` struct in kunit/test.h and in
`kunit_attributes` in kunit/try-catch.h and check for the
`try_catch->try_result` code and the named flag to detect if there was a
panic in `kunit_try_catch_run` function.

2. Allow same test name with different #[cfg(...)]:

When testing `#[should_panic]` in `bitmap.rs` (check the last patch of
the series) I found that the test that was supposed to panic had the
same name as another one, but they were run on different configurations.
This caused the following compilation error:

ERROR:root:error[E0428]: the name `kunit_rust_wrapper_owned_bitmap_out_of_bounds` is defined multiple times
   --> ../rust/kernel/bitmap.rs:503:1
    |
503 | #[macros::kunit_tests(rust_kernel_bitmap)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `kunit_rust_wrapper_owned_bitmap_out_of_bounds` redefined here
    |
    = note: `kunit_rust_wrapper_owned_bitmap_out_of_bounds` must be defined only once in the value namespace of this module
    = note: this error originates in the attribute macro `macros::kunit_tests` (in Nightly builds, run with -Z macro-backtrace for more info)

Now, only the tests with an active `#[cfg(...)]` will be executed by the
runner. Tests with an inactive `#[cfg(...)]` will not appear in the
report since they are not added to the TEST_CASES array.

[1] https://github.com/Rust-for-Linux/linux/blob/fd73f4a6659897191fa0d40695fe370925dd3780/rust/kernel/bitmap.rs#L592-L600
[2] https://doc.rust-lang.org/rust-by-example/testing/unit_testing.html#testing-panics
[3] https://lore.kernel.org/all/DM41PHVITKOG.3I6P2X8048BEP@xxxxxxxxx/
[4] https://github.com/Rust-for-Linux/linux/blob/fd73f4a6659897191fa0d40695fe370925dd3780/rust/kernel/kunit.rs#L129-L136

Signed-off-by: Nicolás Antinori <nico.antinori.7@xxxxxxxxx>
---
Nicolás Antinori (3):
      rust: kunit: add #[should_panic] support
      rust: kunit: allow same test name with different #[cfg(...)]
      rust: bitmap: kunit: uncomment owned_bitmap_out_of_bounds panic case

 include/kunit/test.h       |  1 +
 include/kunit/try-catch.h  |  3 ++
 lib/kunit/attributes.c     | 18 ++++++++++++
 lib/kunit/kunit-test.c     |  3 ++
 lib/kunit/test.c           |  2 ++
 lib/kunit/try-catch-impl.h |  2 ++
 lib/kunit/try-catch.c      | 14 +++++----
 rust/kernel/bitmap.rs      | 21 +++++++------
 rust/kernel/kunit.rs       | 73 ++++++++++++++++++++++++++++++++++++++++++++--
 rust/macros/kunit.rs       | 67 +++++++++++++++++++++++++++++-------------
 10 files changed, 164 insertions(+), 40 deletions(-)
---
base-commit: 65ba8f34ec886ec72b2c07ddc8cf3d815c32869d
change-id: 20261029-rust_kunit_v6_send-d0353c1615f9

Best regards,
-- 
Nicolás Antinori <nico.antinori.7@xxxxxxxxx>