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

[Nicolás Antinori]

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:
- RFC patch: [3]

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
check for the `try_catch->try_result` code and the named flag to detect
if there was a panic in `lib/kunit/test.c::kunit_run_case_catch_errors`
function.

The difference with the previous version [3] is that now, almost
everything is handled in the C side, meaning that we don't have a
separate `#[panic_handler]` when KUnit tests are active. In other words
there's no need of a Rust side panic handler because the C side catches
Rust's panics too, since the `#[panic_hanlder]` executes a
bindings::BUG().

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/rust-for-linux/cover.1789500084.git.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 +
 lib/kunit/attributes.c | 18 ++++++++++++++++
 lib/kunit/test.c       |  5 +++++
 rust/kernel/bitmap.rs  | 40 ++++++++++++++++-------------------
 rust/kernel/kunit.rs   | 37 ++++++++++++++++++++++++++++++++
 rust/macros/kunit.rs   | 48 +++++++++++++++++++++++++++++++++---------
 6 files changed, 117 insertions(+), 32 deletions(-)

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2.47.3