[PATCH v2 1/3] rust: kunit: use `file!()` inside `kunit_assert!`

[Gary Guo <gary@garyguo.net>]

This parameter is needed currently because doctests want to override the
file. Simplify it by changing it to use `file!()`. Have doctests override
`file!()` macro to achieve the current behavior.

This allows us to remove the `file` helper and associated Kconfig options.

Reviewed-by: David Gow <david@davidgow.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
---
 Documentation/rust/general-information.rst |  4 ++--
 init/Kconfig                               |  3 ---
 rust/kernel/kunit.rs                       |  9 +++++----
 rust/macros/helpers.rs                     | 16 ----------------
 rust/macros/kunit.rs                       |  5 ++---
 rust/macros/lib.rs                         |  5 -----
 scripts/rustdoc_test_gen.rs                | 10 ++++++++--
 7 files changed, 17 insertions(+), 35 deletions(-)

diff --git a/Documentation/rust/general-information.rst b/Documentation/rust/general-information.rst
index 09234bed272c..20e3178ebfd4 100644
--- a/Documentation/rust/general-information.rst
+++ b/Documentation/rust/general-information.rst
@@ -157,5 +157,5 @@ numerical comparisons, one may define a new Kconfig symbol:
 
 .. code-block:: kconfig
 
-	config RUSTC_HAS_SPAN_FILE
-		def_bool RUSTC_VERSION >= 108800
+	config RUSTC_HAS_FILE_AS_C_STR
+		def_bool RUSTC_VERSION >= 109100
diff --git a/init/Kconfig b/init/Kconfig
index 8583d9f06c52..24b019104d88 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -178,9 +178,6 @@ config LD_CAN_USE_KEEP_IN_OVERLAY
 	# https://github.com/llvm/llvm-project/pull/130661
 	def_bool LD_IS_BFD || LLD_VERSION >= 210000
 
-config RUSTC_HAS_SPAN_FILE
-	def_bool RUSTC_VERSION >= 108800
-
 config RUSTC_HAS_UNNECESSARY_TRANSMUTES
 	def_bool RUSTC_VERSION >= 108800
 
diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 91eaff8c186a..12084873b51e 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -58,14 +58,15 @@ pub fn info(args: fmt::Arguments<'_>) {
 #[doc(hidden)]
 #[macro_export]
 macro_rules! kunit_assert {
-    ($name:literal, $file:literal, $diff:expr, $condition:expr $(,)?) => {
+    ($name:literal, $diff:expr, $condition:expr $(,)?) => {
         'out: {
             // Do nothing if the condition is `true`.
             if $condition {
                 break 'out;
             }
 
-            static FILE: &'static $crate::str::CStr = $file;
+            // Use `file!()` instead of `::core::file!()` here so it can be overridden.
+            static FILE: &'static $crate::str::CStr = $crate::c_str!(file!());
             static LINE: i32 = ::core::line!() as i32 - $diff;
             static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));
 
@@ -164,10 +165,10 @@ unsafe impl Sync for UnaryAssert {}
 #[doc(hidden)]
 #[macro_export]
 macro_rules! kunit_assert_eq {
-    ($name:literal, $file:literal, $diff:expr, $left:expr, $right:expr $(,)?) => {{
+    ($name:literal, $diff:expr, $left:expr, $right:expr $(,)?) => {{
         // For the moment, we just forward to the expression assert because, for binary asserts,
         // KUnit supports only a few types (e.g. integers).
-        $crate::kunit_assert!($name, $file, $diff, $left == $right);
+        $crate::kunit_assert!($name, $diff, $left == $right);
     }};
 }
 
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
index d18fbf4daa0a..8cc9a20f470e 100644
--- a/rust/macros/helpers.rs
+++ b/rust/macros/helpers.rs
@@ -38,22 +38,6 @@ pub(crate) fn value(&self) -> String {
     }
 }
 
-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()
-    }
-}
-
 /// Obtain all `#[cfg]` attributes.
 pub(crate) fn gather_cfg_attrs(attr: &[Attribute]) -> impl Iterator<Item = &Attribute> + '_ {
     attr.iter().filter(|a| a.path().is_ident("cfg"))
diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
index ae20ed6768f1..936eff014870 100644
--- a/rust/macros/kunit.rs
+++ b/rust/macros/kunit.rs
@@ -109,12 +109,11 @@ pub(crate) fn kunit_tests(test_suite: Ident, mut module: ItemMod) -> Result<Toke
         // Before the test, override usual `assert!` and `assert_eq!` macros with ones that call
         // KUnit instead.
         let test_str = test.to_string();
-        let path = CString::new(crate::helpers::file()).expect("file path cannot contain NUL");
         processed_items.push(parse_quote! {
             #[allow(unused)]
             macro_rules! assert {
                 ($cond:expr $(,)?) => {{
-                    kernel::kunit_assert!(#test_str, #path, 0, $cond);
+                    kernel::kunit_assert!(#test_str, 0, $cond);
                 }}
             }
         });
@@ -122,7 +121,7 @@ macro_rules! assert {
             #[allow(unused)]
             macro_rules! assert_eq {
                 ($left:expr, $right:expr $(,)?) => {{
-                    kernel::kunit_assert_eq!(#test_str, #path, 0, $left, $right);
+                    kernel::kunit_assert_eq!(#test_str, 0, $left, $right);
                 }}
             }
         });
diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
index 24f96feaeb34..6916195f0051 100644
--- a/rust/macros/lib.rs
+++ b/rust/macros/lib.rs
@@ -8,11 +8,6 @@
 
 // Stable since Rust 1.87.0.
 #![feature(extract_if)]
-//
-// Stable since Rust 1.88.0 under a different name, `proc_macro_span_file`,
-// which was added in Rust 1.88.0. This is why `cfg_attr` is used here, i.e.
-// to avoid depending on the full `proc_macro_span` on Rust >= 1.88.0.
-#![cfg_attr(not(CONFIG_RUSTC_HAS_SPAN_FILE), feature(proc_macro_span))]
 
 mod concat_idents;
 mod export;
diff --git a/scripts/rustdoc_test_gen.rs b/scripts/rustdoc_test_gen.rs
index d087c0d9fcb3..bb57745ec339 100644
--- a/scripts/rustdoc_test_gen.rs
+++ b/scripts/rustdoc_test_gen.rs
@@ -176,12 +176,18 @@ fn main() {
             r#"/// Generated `{name}` KUnit test case from a Rust documentation test.
 #[no_mangle]
 pub extern "C" fn {kunit_name}(__kunit_test: *mut ::kernel::bindings::kunit) {{
+    /// Overrides the usual [`file!`] macro with one that expands to the real path.
+    #[allow(unused)]
+    macro_rules! file {{
+        () => {{ "{real_path}" }}
+    }}
+
     /// Overrides the usual [`assert!`] macro with one that calls KUnit instead.
     #[allow(unused)]
     macro_rules! assert {{
         ($cond:expr $(,)?) => {{{{
             ::kernel::kunit_assert!(
-                "{kunit_name}", c"{real_path}", __DOCTEST_ANCHOR - {line}, $cond
+                "{kunit_name}", __DOCTEST_ANCHOR - {line}, $cond
             );
         }}}}
     }}
@@ -191,7 +197,7 @@ macro_rules! assert {{
     macro_rules! assert_eq {{
         ($left:expr, $right:expr $(,)?) => {{{{
             ::kernel::kunit_assert_eq!(
-                "{kunit_name}", c"{real_path}", __DOCTEST_ANCHOR - {line}, $left, $right
+                "{kunit_name}", __DOCTEST_ANCHOR - {line}, $left, $right
             );
         }}}}
     }}

-- 
2.54.0