Message-ID: <CAJ-ks9nAT5ETe3qM-DcY-YqES-pTK0RdMAY_fn1jT0_Dv1HkTQ@mail.gmail.com>
Date: Fri, 14 Feb 2025 09:40:58 -0500
From: Tamir Duberstein <tamird@...il.com>
To: David Gow <davidgow@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, José Expósito <jose.exposito89@...il.com>, 
	Rae Moar <rmoar@...gle.com>, Boqun Feng <boqun.feng@...il.com>, 
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>, 
	Benno Lossin <benno.lossin@...ton.me>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Alice Ryhl <aliceryhl@...gle.com>, Matt Gilbride <mattgilbride@...gle.com>, 
	Brendan Higgins <brendan.higgins@...ux.dev>, kunit-dev@...glegroups.com, 
	linux-kselftest@...r.kernel.org, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/3] rust: macros: add macro to easily run KUnit tests

On Fri, Feb 14, 2025 at 2:41 AM David Gow <davidgow@...gle.com> wrote:
>
> From: José Expósito <jose.exposito89@...il.com>
>
> Add a new procedural macro (`#[kunit_tests(kunit_test_suit_name)]`) to
> run KUnit tests using a user-space like syntax.
>
> The macro, that should be used on modules, transforms every `#[test]`
> in a `kunit_case!` and adds a `kunit_unsafe_test_suite!` registering
> all of them.
>
> The only difference with user-space tests is that instead of using
> `#[cfg(test)]`, `#[kunit_tests(kunit_test_suit_name)]` is used.
>
> Note that `#[cfg(CONFIG_KUNIT)]` is added so the test module is not
> compiled when `CONFIG_KUNIT` is set to `n`.
>
> Reviewed-by: David Gow <davidgow@...gle.com>
> Signed-off-by: José Expósito <jose.exposito89@...il.com>
> Co-developed-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> Co-developed-by: Miguel Ojeda <ojeda@...nel.org>
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
> Signed-off-by: David Gow <davidgow@...gle.com>
> ---
> Changes since v5:
> https://lore.kernel.org/all/20241213081035.2069066-3-davidgow@google.com/
> - Fix some rustfmt-related formatting shenanigans. (Thanks, Miguel)
> - Fix some documentation comment formatting as well. (Thanks, Miguel)
> - Tidy up the generated code to avoid unneeded &mut[] everywhere.
>   (Thanks, Miguel)
> - Fix a new clippy warning for using .as_bytes().len() instead of .len()
>   directly.
>
> Changes since v4:
> https://lore.kernel.org/linux-kselftest/20241101064505.3820737-3-davidgow@google.com/
> - Rebased against 6.13-rc1
> - "Expect" that the sample assert_eq!(1+1, 2) produces a clippy warning
>   due to a redundant assertion. (Thanks Boqun, Miguel)
>
> Changes since v3:
> https://lore.kernel.org/linux-kselftest/20241030045719.3085147-6-davidgow@google.com/
> - The #[kunit_tests()] macro now preserves span information, so
>   errors can be better reported. (Thanks, Boqun!)
> - The example test has been replaced to no longer use assert_eq!() with
>   a constant bool argument (which triggered a clippy warning now we
>   have the span info). It now checks 1 + 1 == 2, to match the C example.
>   - (The in_kunit_test() test in the next patch uses assert!() to check
>     a bool, so having something different here seemed to make a better
>     example.)
>
> Changes since v2:
> https://lore.kernel.org/linux-kselftest/20241029092422.2884505-3-davidgow@google.com/
> - Include missing rust/macros/kunit.rs file from v2. (Thanks Boqun!)
> - The proc macro now emits an error if the suite name is too long.
>
> Changes since v1:
> https://lore.kernel.org/lkml/20230720-rustbind-v1-2-c80db349e3b5@google.com/
> - Rebased on top of rust-next
> - Make use of the new const functions, rather than the kunit_case!()
>   macro.
>
> ---
>  MAINTAINERS          |   1 +
>  rust/kernel/kunit.rs |  12 ++++
>  rust/macros/kunit.rs | 161 +++++++++++++++++++++++++++++++++++++++++++
>  rust/macros/lib.rs   |  29 ++++++++
>  4 files changed, 203 insertions(+)
>  create mode 100644 rust/macros/kunit.rs
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c8d9e8187eb0..4e7a6d2f2c49 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12677,6 +12677,7 @@ F:      Documentation/dev-tools/kunit/
>  F:     include/kunit/
>  F:     lib/kunit/
>  F:     rust/kernel/kunit.rs
> +F:     rust/macros/kunit.rs
>  F:     scripts/rustdoc_test_*
>  F:     tools/testing/kunit/
>
> diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> index d34a92075174..9e27b74a605b 100644
> --- a/rust/kernel/kunit.rs
> +++ b/rust/kernel/kunit.rs
> @@ -40,6 +40,8 @@ pub fn info(args: fmt::Arguments<'_>) {
>      }
>  }
>
> +use macros::kunit_tests;
> +
>  /// Asserts that a boolean expression is `true` at runtime.
>  ///
>  /// Public but hidden since it should only be used from generated tests.
> @@ -275,6 +277,7 @@ macro_rules! kunit_unsafe_test_suite {
>                  };
>
>              #[used]
> +            #[allow(unused_unsafe)]
>              #[link_section = ".kunit_test_suites"]
>              static mut KUNIT_TEST_SUITE_ENTRY: *const ::kernel::bindings::kunit_suite =
>                  // SAFETY: `KUNIT_TEST_SUITE` is static.
> @@ -282,3 +285,12 @@ macro_rules! kunit_unsafe_test_suite {
>          };
>      };
>  }
> +
> +#[kunit_tests(rust_kernel_kunit)]
> +mod tests {
> +    #[test]
> +    fn rust_test_kunit_example_test() {
> +        #![expect(clippy::eq_op)]
> +        assert_eq!(1 + 1, 2);
> +    }
> +}
> diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
> new file mode 100644
> index 000000000000..4f553ecf40c0
> --- /dev/null
> +++ b/rust/macros/kunit.rs
> @@ -0,0 +1,161 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Procedural macro to run KUnit tests using a user-space like syntax.
> +//!
> +//! Copyright (c) 2023 José Expósito <jose.exposito89@...il.com>
> +
> +use proc_macro::{Delimiter, Group, TokenStream, TokenTree};
> +use std::fmt::Write;
> +
> +pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {
> +    let attr = attr.to_string();
> +
> +    if attr.is_empty() {
> +        panic!("Missing test name in `#[kunit_tests(test_name)]` macro")
> +    }
> +
> +    if attr.len() > 255 {
> +        panic!(
> +            "The test suite name `{}` exceeds the maximum length of 255 bytes",
> +            attr
> +        )
> +    }
> +
> +    let mut tokens: Vec<_> = ts.into_iter().collect();
> +
> +    // Scan for the `mod` keyword.
> +    tokens
> +        .iter()
> +        .find_map(|token| match token {
> +            TokenTree::Ident(ident) => match ident.to_string().as_str() {
> +                "mod" => Some(true),
> +                _ => None,
> +            },
> +            _ => None,
> +        })
> +        .expect("`#[kunit_tests(test_name)]` attribute should only be applied to modules");
> +
> +    // Retrieve the main body. The main body should be the last token tree.
> +    let body = match tokens.pop() {
> +        Some(TokenTree::Group(group)) if group.delimiter() == Delimiter::Brace => group,
> +        _ => panic!("Cannot locate main body of module"),
> +    };
> +
> +    // Get the functions set as tests. Search for `[test]` -> `fn`.
> +    let mut body_it = body.stream().into_iter();
> +    let mut tests = Vec::new();
> +    while let Some(token) = body_it.next() {
> +        match token {
> +            TokenTree::Group(ident) if ident.to_string() == "[test]" => match body_it.next() {
> +                Some(TokenTree::Ident(ident)) if ident.to_string() == "fn" => {
> +                    let test_name = match body_it.next() {
> +                        Some(TokenTree::Ident(ident)) => ident.to_string(),
> +                        _ => continue,
> +                    };
> +                    tests.push(test_name);
> +                }
> +                _ => continue,
> +            },
> +            _ => (),
> +        }
> +    }
> +
> +    // Add `#[cfg(CONFIG_KUNIT)]` before the module declaration.
> +    let config_kunit = "#[cfg(CONFIG_KUNIT)]".to_owned().parse().unwrap();
> +    tokens.insert(
> +        0,
> +        TokenTree::Group(Group::new(Delimiter::None, config_kunit)),
> +    );
> +
> +    // Generate the test KUnit test suite and a test case for each `#[test]`.
> +    // The code generated for the following test module:
> +    //
> +    // ```
> +    // #[kunit_tests(kunit_test_suit_name)]
> +    // mod tests {
> +    //     #[test]
> +    //     fn foo() {
> +    //         assert_eq!(1, 1);
> +    //     }
> +    //
> +    //     #[test]
> +    //     fn bar() {
> +    //         assert_eq!(2, 2);
> +    //     }
> +    // }
> +    // ```
> +    //
> +    // Looks like:
> +    //
> +    // ```
> +    // unsafe extern "C" fn kunit_rust_wrapper_foo(_test: *mut kernel::bindings::kunit) { foo(); }
> +    // unsafe extern "C" fn kunit_rust_wrapper_bar(_test: *mut kernel::bindings::kunit) { bar(); }
> +    //
> +    // static mut TEST_CASES: [kernel::bindings::kunit_case; 3] = [
> +    //     kernel::kunit::kunit_case(kernel::c_str!("foo"), kunit_rust_wrapper_foo),
> +    //     kernel::kunit::kunit_case(kernel::c_str!("bar"), kunit_rust_wrapper_bar),
> +    //     kernel::kunit::kunit_case_null(),
> +    // ];
> +    //
> +    // kernel::kunit_unsafe_test_suite!(kunit_test_suit_name, TEST_CASES);
> +    // ```

This is a really helpful comment. It got me wondering: can we have
host-side unit tests for our proc macros? Code is better than
comments, of course.

> +    let mut kunit_macros = "".to_owned();
> +    let mut test_cases = "".to_owned();
> +    for test in &tests {
> +        let kunit_wrapper_fn_name = format!("kunit_rust_wrapper_{}", test);
> +        let kunit_wrapper = format!(
> +            "unsafe extern \"C\" fn {}(_test: *mut kernel::bindings::kunit) {{ {}(); }}",
> +            kunit_wrapper_fn_name, test
> +        );
> +        writeln!(kunit_macros, "{kunit_wrapper}").unwrap();
> +        writeln!(
> +            test_cases,
> +            "    kernel::kunit::kunit_case(kernel::c_str!(\"{}\"), {}),",
> +            test, kunit_wrapper_fn_name
> +        )
> +        .unwrap();
> +    }
> +
> +    writeln!(kunit_macros).unwrap();
> +    writeln!(
> +        kunit_macros,
> +        "static mut TEST_CASES: [kernel::bindings::kunit_case; {}] = [\n{test_cases}    kernel::kunit::kunit_case_null(),\n];",
> +        tests.len() + 1
> +    )
> +    .unwrap();
> +
> +    writeln!(
> +        kunit_macros,
> +        "kernel::kunit_unsafe_test_suite!({attr}, TEST_CASES);"
> +    )
> +    .unwrap();
> +
> +    // Remove the `#[test]` macros.

This makes sense. I wonder if we should think about being able to
declare a test that runs both on host and in KUnit.



> +    // We do this at a token level, in order to preserve span information.
> +    let mut new_body = vec![];
> +    let mut body_it = body.stream().into_iter();
> +
> +    while let Some(token) = body_it.next() {
> +        match token {
> +            TokenTree::Punct(ref c) if c.as_char() == '#' => match body_it.next() {
> +                Some(TokenTree::Group(group)) if group.to_string() == "[test]" => (),
> +                Some(next) => {
> +                    new_body.extend([token, next]);
> +                }
> +                _ => {
> +                    new_body.push(token);
> +                }
> +            },
> +            _ => {
> +                new_body.push(token);
> +            }
> +        }
> +    }
> +
> +    let mut new_body = TokenStream::from_iter(new_body);
> +    new_body.extend::<TokenStream>(kunit_macros.parse().unwrap());
> +
> +    tokens.push(TokenTree::Group(Group::new(Delimiter::Brace, new_body)));
> +
> +    tokens.into_iter().collect()
> +}
> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index d61bc6a56425..50b58259c577 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -10,6 +10,7 @@
>  mod quote;
>  mod concat_idents;
>  mod helpers;
> +mod kunit;
>  mod module;
>  mod paste;
>  mod pin_data;
> @@ -492,3 +493,31 @@ pub fn paste(input: TokenStream) -> TokenStream {
>  pub fn derive_zeroable(input: TokenStream) -> TokenStream {
>      zeroable::derive(input)
>  }
> +
> +/// Registers a KUnit test suite and its test cases using a user-space like syntax.
> +///
> +/// This macro should be used on modules. If `CONFIG_KUNIT` (in `.config`) is `n`, the target module
> +/// is ignored.
> +///
> +/// # Examples
> +///
> +/// ```ignore
> +/// # use macros::kunit_tests;
> +///
> +/// #[kunit_tests(kunit_test_suit_name)]
> +/// mod tests {
> +///     #[test]
> +///     fn foo() {
> +///         assert_eq!(1, 1);
> +///     }
> +///
> +///     #[test]
> +///     fn bar() {
> +///         assert_eq!(2, 2);
> +///     }
> +/// }
> +/// ```
> +#[proc_macro_attribute]
> +pub fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {
> +    kunit::kunit_tests(attr, ts)
> +}
> --
> 2.48.1.601.g30ceb7b040-goog
>
>

Powered by blists - more mailing lists