Re: [PATCH 1/7] rust: kunit: support KUnit-mapped `assert!` macros in `#[test]`s

On Sat, 3 May 2025 at 05:51, Miguel Ojeda ojeda@kernel.org wrote:

The KUnit `#[test]` support that landed recently is very basic and does not map the `assert*!` macros into KUnit like the doctests do, so they panic at the moment.

Thus implement the custom mapping in a similar way to doctests, reusing the infrastructure there.

In Rust 1.88.0, the `file()` method in `Span` may be stable [1]. However, it was changed recently (from `SourceFile`), so we need to do something different in previous versions. Thus create a helper for it and use it to get the path.

With this, a failing test suite like:

#[kunit_tests(my_test_suite)]
mod tests {
    use super::*;

    #[test]
    fn my_first_test() {
        assert_eq!(42, 43);
    }

    #[test]
    fn my_second_test() {
        assert!(42 >= 43);
    }
}

will properly map back to KUnit, printing something like:

[    1.924325]     KTAP version 1
[    1.924421]     # Subtest: my_test_suite
[    1.924506]     # speed: normal
[    1.924525]     1..2
[    1.926385]     # my_first_test: ASSERTION FAILED at rust/kernel/lib.rs:251
[    1.926385]     Expected 42 == 43 to be true, but is false
[    1.928026]     # my_first_test.speed: normal
[    1.928075]     not ok 1 my_first_test
[    1.928723]     # my_second_test: ASSERTION FAILED at rust/kernel/lib.rs:256
[    1.928723]     Expected 42 >= 43 to be true, but is false
[    1.929834]     # my_second_test.speed: normal
[    1.929868]     not ok 2 my_second_test
[    1.930032] # my_test_suite: pass:0 fail:2 skip:0 total:2
[    1.930153] # Totals: pass:0 fail:2 skip:0 total

Link: https://github.com/rust-lang/rust/pull/140514 [1] Signed-off-by: Miguel Ojeda ojeda@kernel.org

---

Nice! While I do think there may still be some cases where we might want to use KUnit-specific macros in the future (particularly if we have more complex, multithreaded test contexts), this is definitely better for most cases.

I also managed to test it against the 1.88 nightly, and the message is looking good.

Reviewed-by: David Gow davidgow@google.com

Cheers, -- David

init/Kconfig | 3 +++ rust/Makefile | 3 ++- rust/kernel/kunit.rs | 1 - rust/macros/helpers.rs | 16 ++++++++++++++++ rust/macros/kunit.rs | 28 +++++++++++++++++++++++++++- rust/macros/lib.rs | 4 ++++ 6 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig index 63f5974b9fa6..5f442c64c47b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -140,6 +140,9 @@ config LD_CAN_USE_KEEP_IN_OVERLAY config RUSTC_HAS_COERCE_POINTEE def_bool RUSTC_VERSION >= 108400

+config RUSTC_HAS_SPAN_FILE

•   def_bool RUSTC_VERSION >= 108800
  

config PAHOLE_VERSION int default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) diff --git a/rust/Makefile b/rust/Makefile index 3aca903a7d08..075b38a24997 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -402,7 +402,8 @@ quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@ -Clink-args='$(call escsq,$(KBUILD_PROCMACROLDFLAGS))' \ --emit=dep-info=$(depfile) --emit=link=$@ --extern proc_macro \ --crate-type proc-macro \

•           --crate-name $(patsubst lib%.$(libmacros_extension),%,$(notdir $@)) $<
  

•           --crate-name $(patsubst lib%.$(libmacros_extension),%,$(notdir $@)) \
  

•           @$(objtree)/include/generated/rustc_cfg $<
  
  

# Procedural macros can only be used with the `rustc` that compiled it. $(obj)/$(libmacros_name): $(src)/macros/lib.rs FORCE diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs index 1604fb6a5b1b..2659895d4c5d 100644 --- a/rust/kernel/kunit.rs +++ b/rust/kernel/kunit.rs @@ -323,7 +323,6 @@ mod tests {

 #[test]
 fn rust_test_kunit_example_test() {

•    #![expect(clippy::eq_op)]
     assert_eq!(1 + 1, 2);
  

  }

diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs index a3ee27e29a6f..57c3b0f0c194 100644 --- a/rust/macros/helpers.rs +++ b/rust/macros/helpers.rs @@ -86,3 +86,19 @@ pub(crate) fn function_name(input: TokenStream) -> Option<Ident> { } None }

+pub(crate) fn file() -> String {

• #[cfg(not(CONFIG_RUSTC_HAS_SPAN_FILE))]
• {

•    proc_macro::Span::call_site()
  

•        .source_file()
  

•        .path()
  

•        .to_string_lossy()
  

•        .into_owned()
  

• }
• #[cfg(CONFIG_RUSTC_HAS_SPAN_FILE)]
• {

•    proc_macro::Span::call_site().file()
  

• }

+} diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs index 4f553ecf40c0..eb4f2afdbe43 100644 --- a/rust/macros/kunit.rs +++ b/rust/macros/kunit.rs @@ -101,6 +101,8 @@ pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream { // ``` let mut kunit_macros = "".to_owned(); let mut test_cases = "".to_owned();

• let mut assert_macros = "".to_owned();
• let path = crate::helpers::file(); for test in &tests { let kunit_wrapper_fn_name = format!("kunit_rust_wrapper_{}", test); let kunit_wrapper = format!(

@@ -114,6 +116,27 @@ pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream { test, kunit_wrapper_fn_name ) .unwrap();

•    writeln!(
  

•        assert_macros,
  

•        r#"
  

+/// Overrides the usual [`assert!`] macro with one that calls KUnit instead. +#[allow(unused)] +macro_rules! assert {{

• ($cond:expr $(,)?) => {{{{

•    kernel::kunit_assert!("{test}", "{path}", 0, $cond);
  

• }}}}

+}}

+/// Overrides the usual [`assert_eq!`] macro with one that calls KUnit instead. +#[allow(unused)] +macro_rules! assert_eq {{

• ($left:expr, $right:expr $(,)?) => {{{{

•    kernel::kunit_assert_eq!("{test}", "{path}", 0, $left, $right);
  

• }}}}

+}}

•    "#
  

•    )
  

•    .unwrap();
  

  }

  writeln!(kunit_macros).unwrap();

@@ -152,7 +175,10 @@ pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream { } }

• let mut new_body = TokenStream::from_iter(new_body);

• let body = new_body;

• let mut new_body = TokenStream::new();

• new_body.extend::<TokenStream>(assert_macros.parse().unwrap());

• new_body.extend(body); new_body.extend::<TokenStream>(kunit_macros.parse().unwrap());

  tokens.push(TokenTree::Group(Group::new(Delimiter::Brace, new_body)));

diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs index 9acaa68c974e..8bd7906276be 100644 --- a/rust/macros/lib.rs +++ b/rust/macros/lib.rs @@ -6,6 +6,10 @@ // and thus add a dependency on `include/config/RUSTC_VERSION_TEXT`, which is // touched by Kconfig when the version string from the compiler changes.

+// TODO: check that when Rust 1.88.0 is released, this would be enough: +// #![cfg_attr(not(CONFIG_RUSTC_HAS_SPAN_FILE), feature(proc_macro_span))] +#![feature(proc_macro_span)]

#[macro_use] mod quote; mod concat_idents; -- 2.49.0