Re: [PATCH 2/3] rust: macros: add macro to easily run KUnit tests

Boqun Feng
2023-07-30T21:50:02Z

On Thu, Jul 20, 2023 at 02:38:53PM +0800, David Gow wrote:
> From: José Expósito <jose.exposito89@gmail.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@google.com>
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>
> ---
> MAINTAINERS | 1 +
> rust/kernel/kunit.rs | 11 ++++
> rust/macros/kunit.rs | 149 +++++++++++++++++++++++++++++++++++++++++++++++++++
> rust/macros/lib.rs | 29 ++++++++++
> 4 files changed, 190 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2a942fe59144..c32ba6b29a96 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11373,6 +11373,7 @@ 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 4cffc71e463b..44ea67028316 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.
> @@ -253,3 +255,12 @@ macro_rules! kunit_unsafe_test_suite {
> };
> };
> }
> +
> +#[kunit_tests(rust_kernel_kunit)]
> +mod tests {
> + #[test]
> + fn rust_test_kunit_kunit_tests() {
> + let running = true;
> + assert_eq!(running, true);
> + }
> +}
> diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
> new file mode 100644
> index 000000000000..69dac253232f
> --- /dev/null
> +++ b/rust/macros/kunit.rs
> @@ -0,0 +1,149 @@
> +// 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@gmail.com>
> +
> +use proc_macro::{Delimiter, Group, TokenStream, TokenTree};
> +use std::fmt::Write;
> +
> +pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {
> + if attr.to_string().is_empty() {
> + panic!("Missing test name in #[kunit_tests(test_name)] macro")
> + }
> +
> + 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();
> + // }
> + // static mut KUNIT_CASE_FOO: kernel::bindings::kunit_case =
> + // kernel::kunit_case!(foo, kunit_rust_wrapper_foo);
> + //
> + // unsafe extern "C" fn kunit_rust_wrapper_bar(_test: * mut kernel::bindings::kunit) {
> + // bar();
> + // }
> + // static mut KUNIT_CASE_BAR: kernel::bindings::kunit_case =
> + // kernel::kunit_case!(bar, kunit_rust_wrapper_bar);
> + //
> + // static mut KUNIT_CASE_NULL: kernel::bindings::kunit_case = kernel::kunit_case!();
> + //
> + // static mut TEST_CASES : &mut[kernel::bindings::kunit_case] = unsafe {
> + // &mut [KUNIT_CASE_FOO, KUNIT_CASE_BAR, KUNIT_CASE_NULL]
> + // };
> + //
> + // kernel::kunit_unsafe_test_suite!(kunit_test_suit_name, TEST_CASES);
> + // ```
> + 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_case_name = format!("KUNIT_CASE_{}", test.to_uppercase());
> + let kunit_wrapper = format!(
> + "unsafe extern \"C\" fn {}(_test: *mut kernel::bindings::kunit) {{ {}(); }}",
> + kunit_wrapper_fn_name, test
> + );
> + let kunit_case = format!(
> + "static mut {}: kernel::bindings::kunit_case = kernel::kunit_case!({}, {});",
> + kunit_case_name, test, kunit_wrapper_fn_name
> + );
> + writeln!(kunit_macros, "{kunit_wrapper}").unwrap();
> + writeln!(kunit_macros, "{kunit_case}").unwrap();
> + writeln!(test_cases, "{kunit_case_name},").unwrap();
> + }
> +
> + writeln!(
> + kunit_macros,
> + "static mut KUNIT_CASE_NULL: kernel::bindings::kunit_case = kernel::kunit_case!();"
> + )
> + .unwrap();
> +
> + writeln!(
> + kunit_macros,
> + "static mut TEST_CASES : &mut[kernel::bindings::kunit_case] = unsafe {{ &mut[{test_cases} KUNIT_CASE_NULL] }};"
> + )
> + .unwrap();
> +
> + writeln!(
> + kunit_macros,
> + "kernel::kunit_unsafe_test_suite!({attr}, TEST_CASES);"
> + )
> + .unwrap();
> +
> + let new_body: TokenStream = vec![body.stream(), kunit_macros.parse().unwrap()]
> + .into_iter()
> + .collect();
> +
> + // Remove the `#[test]` macros.
> + let new_body = new_body.to_string().replace("#[test]", "");

I've played this with some extra tests, one thing I notice is that
Span/code location information is lost if we do this, for example, if I
have a compile error in the test code (I introduced one on purpose in
the `rust_kernel_kunit` test), I will get information like:

error[E0384]: cannot assign twice to immutable variable `running`
--> ../rust/kernel/kunit.rs:329:1
|
329 | #[kunit_tests(rust_kernel_kunit)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| cannot assign twice to immutable variable
| help: consider making this binding mutable: `mut running`

the location information is not very usefull. However if we do the
following:

diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
index 69dac253232f..913879765d24 100644
--- a/rust/macros/kunit.rs
+++ b/rust/macros/kunit.rs
@@ -134,15 +134,29 @@ pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {
)
.unwrap();

- let new_body: TokenStream = vec![body.stream(), kunit_macros.parse().unwrap()]
- .into_iter()
- .collect();
-
// Remove the `#[test]` macros.
- let new_body = new_body.to_string().replace("#[test]", "");
+ 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(g)) if g.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.parse().unwrap(),
+ new_body
)));

tokens.into_iter().collect()

then we get better information:

--> ../rust/kernel/kunit.rs:335:13
|
335 | let running = true;
| ^^^^^^^
|
= help: maybe it is overwritten before being read?
= note: `#[warn(unused_assignments)]` on by default

error[E0384]: cannot assign twice to immutable variable `running`
--> ../rust/kernel/kunit.rs:336:9
|
335 | let running = true;
| -------
| |
| first assignment to `running`
| help: consider making this binding mutable: `mut running`
336 | running = false;
| ^^^^^^^^^^^^^^^ cannot assign twice to immutable variable

Regards,
Boqun

> + tokens.push(TokenTree::Group(Group::new(
> + Delimiter::Brace,
> + new_body.parse().unwrap(),
> + )));
> +
> + tokens.into_iter().collect()
> +}
> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index 3fc74cb4ea19..cd0b720514ff 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -6,6 +6,7 @@
> mod quote;
> mod concat_idents;
> mod helpers;
> +mod kunit;
> mod module;
> mod pin_data;
> mod pinned_drop;
> @@ -246,3 +247,31 @@ pub fn pin_data(inner: TokenStream, item: TokenStream) -> TokenStream {
> pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
> pinned_drop::pinned_drop(args, 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)
> +}
>
> --
> 2.41.0.255.g8b1d071c50-goog
>