xref: /openbmc/linux/scripts/rustdoc_test_gen.rs (revision a66d733d)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 //! Generates KUnit tests from saved `rustdoc`-generated tests.
4 //!
5 //! KUnit passes a context (`struct kunit *`) to each test, which should be forwarded to the other
6 //! KUnit functions and macros.
7 //!
8 //! However, we want to keep this as an implementation detail because:
9 //!
10 //!   - Test code should not care about the implementation.
11 //!
12 //!   - Documentation looks worse if it needs to carry extra details unrelated to the piece
13 //!     being described.
14 //!
15 //!   - Test code should be able to define functions and call them, without having to carry
16 //!     the context.
17 //!
18 //!   - Later on, we may want to be able to test non-kernel code (e.g. `core`, `alloc` or
19 //!     third-party crates) which likely use the standard library `assert*!` macros.
20 //!
21 //! For this reason, instead of the passed context, `kunit_get_current_test()` is used instead
22 //! (i.e. `current->kunit_test`).
23 //!
24 //! Note that this means other threads/tasks potentially spawned by a given test, if failing, will
25 //! report the failure in the kernel log but will not fail the actual test. Saving the pointer in
26 //! e.g. a `static` per test does not fully solve the issue either, because currently KUnit does
27 //! not support assertions (only expectations) from other tasks. Thus leave that feature for
28 //! the future, which simplifies the code here too. We could also simply not allow `assert`s in
29 //! other tasks, but that seems overly constraining, and we do want to support them, eventually.
30 
31 use std::{
32     fs,
33     fs::File,
34     io::{BufWriter, Read, Write},
35     path::{Path, PathBuf},
36 };
37 
38 /// Find the real path to the original file based on the `file` portion of the test name.
39 ///
40 /// `rustdoc` generated `file`s look like `sync_locked_by_rs`. Underscores (except the last one)
41 /// may represent an actual underscore in a directory/file, or a path separator. Thus the actual
42 /// file might be `sync_locked_by.rs`, `sync/locked_by.rs`, `sync_locked/by.rs` or
43 /// `sync/locked/by.rs`. This function walks the file system to determine which is the real one.
44 ///
45 /// This does require that ambiguities do not exist, but that seems fair, especially since this is
46 /// all supposed to be temporary until `rustdoc` gives us proper metadata to build this. If such
47 /// ambiguities are detected, they are diagnosed and the script panics.
find_real_path<'a>(srctree: &Path, valid_paths: &'a mut Vec<PathBuf>, file: &str) -> &'a str48 fn find_real_path<'a>(srctree: &Path, valid_paths: &'a mut Vec<PathBuf>, file: &str) -> &'a str {
49     valid_paths.clear();
50 
51     let potential_components: Vec<&str> = file.strip_suffix("_rs").unwrap().split('_').collect();
52 
53     find_candidates(srctree, valid_paths, Path::new(""), &potential_components);
54     fn find_candidates(
55         srctree: &Path,
56         valid_paths: &mut Vec<PathBuf>,
57         prefix: &Path,
58         potential_components: &[&str],
59     ) {
60         // The base case: check whether all the potential components left, joined by underscores,
61         // is a file.
62         let joined_potential_components = potential_components.join("_") + ".rs";
63         if srctree
64             .join("rust/kernel")
65             .join(prefix)
66             .join(&joined_potential_components)
67             .is_file()
68         {
69             // Avoid `srctree` here in order to keep paths relative to it in the KTAP output.
70             valid_paths.push(
71                 Path::new("rust/kernel")
72                     .join(prefix)
73                     .join(joined_potential_components),
74             );
75         }
76 
77         // In addition, check whether each component prefix, joined by underscores, is a directory.
78         // If not, there is no need to check for combinations with that prefix.
79         for i in 1..potential_components.len() {
80             let (components_prefix, components_rest) = potential_components.split_at(i);
81             let prefix = prefix.join(components_prefix.join("_"));
82             if srctree.join("rust/kernel").join(&prefix).is_dir() {
83                 find_candidates(srctree, valid_paths, &prefix, components_rest);
84             }
85         }
86     }
87 
88     assert!(
89         valid_paths.len() > 0,
90         "No path candidates found. This is likely a bug in the build system, or some files went \
91         away while compiling."
92     );
93 
94     if valid_paths.len() > 1 {
95         eprintln!("Several path candidates found:");
96         for path in valid_paths {
97             eprintln!("    {path:?}");
98         }
99         panic!(
100             "Several path candidates found, please resolve the ambiguity by renaming a file or \
101             folder."
102         );
103     }
104 
105     valid_paths[0].to_str().unwrap()
106 }
107 
main()108 fn main() {
109     let srctree = std::env::var("srctree").unwrap();
110     let srctree = Path::new(&srctree);
111 
112     let mut paths = fs::read_dir("rust/test/doctests/kernel")
113         .unwrap()
114         .map(|entry| entry.unwrap().path())
115         .collect::<Vec<_>>();
116 
117     // Sort paths.
118     paths.sort();
119 
120     let mut rust_tests = String::new();
121     let mut c_test_declarations = String::new();
122     let mut c_test_cases = String::new();
123     let mut body = String::new();
124     let mut last_file = String::new();
125     let mut number = 0;
126     let mut valid_paths: Vec<PathBuf> = Vec::new();
127     let mut real_path: &str = "";
128     for path in paths {
129         // The `name` follows the `{file}_{line}_{number}` pattern (see description in
130         // `scripts/rustdoc_test_builder.rs`). Discard the `number`.
131         let name = path.file_name().unwrap().to_str().unwrap().to_string();
132 
133         // Extract the `file` and the `line`, discarding the `number`.
134         let (file, line) = name.rsplit_once('_').unwrap().0.rsplit_once('_').unwrap();
135 
136         // Generate an ID sequence ("test number") for each one in the file.
137         if file == last_file {
138             number += 1;
139         } else {
140             number = 0;
141             last_file = file.to_string();
142 
143             // Figure out the real path, only once per file.
144             real_path = find_real_path(srctree, &mut valid_paths, file);
145         }
146 
147         // Generate a KUnit name (i.e. test name and C symbol) for this test.
148         //
149         // We avoid the line number, like `rustdoc` does, to make things slightly more stable for
150         // bisection purposes. However, to aid developers in mapping back what test failed, we will
151         // print a diagnostics line in the KTAP report.
152         let kunit_name = format!("rust_doctest_kernel_{file}_{number}");
153 
154         // Read the test's text contents to dump it below.
155         body.clear();
156         File::open(path).unwrap().read_to_string(&mut body).unwrap();
157 
158         // Calculate how many lines before `main` function (including the `main` function line).
159         let body_offset = body
160             .lines()
161             .take_while(|line| !line.contains("fn main() {"))
162             .count()
163             + 1;
164 
165         use std::fmt::Write;
166         write!(
167             rust_tests,
168             r#"/// Generated `{name}` KUnit test case from a Rust documentation test.
169 #[no_mangle]
170 pub extern "C" fn {kunit_name}(__kunit_test: *mut kernel::bindings::kunit) {{
171     /// Overrides the usual [`assert!`] macro with one that calls KUnit instead.
172     #[allow(unused)]
173     macro_rules! assert {{
174         ($cond:expr $(,)?) => {{{{
175             kernel::kunit_assert!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $cond);
176         }}}}
177     }}
178 
179     /// Overrides the usual [`assert_eq!`] macro with one that calls KUnit instead.
180     #[allow(unused)]
181     macro_rules! assert_eq {{
182         ($left:expr, $right:expr $(,)?) => {{{{
183             kernel::kunit_assert_eq!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $left, $right);
184         }}}}
185     }}
186 
187     // Many tests need the prelude, so provide it by default.
188     #[allow(unused)]
189     use kernel::prelude::*;
190 
191     // Unconditionally print the location of the original doctest (i.e. rather than the location in
192     // the generated file) so that developers can easily map the test back to the source code.
193     //
194     // This information is also printed when assertions fail, but this helps in the successful cases
195     // when the user is running KUnit manually, or when passing `--raw_output` to `kunit.py`.
196     //
197     // This follows the syntax for declaring test metadata in the proposed KTAP v2 spec, which may
198     // be used for the proposed KUnit test attributes API. Thus hopefully this will make migration
199     // easier later on.
200     kernel::kunit::info(format_args!("    # {kunit_name}.location: {real_path}:{line}\n"));
201 
202     /// The anchor where the test code body starts.
203     #[allow(unused)]
204     static __DOCTEST_ANCHOR: i32 = core::line!() as i32 + {body_offset} + 1;
205     {{
206         {body}
207         main();
208     }}
209 }}
210 
211 "#
212         )
213         .unwrap();
214 
215         write!(c_test_declarations, "void {kunit_name}(struct kunit *);\n").unwrap();
216         write!(c_test_cases, "    KUNIT_CASE({kunit_name}),\n").unwrap();
217     }
218 
219     let rust_tests = rust_tests.trim();
220     let c_test_declarations = c_test_declarations.trim();
221     let c_test_cases = c_test_cases.trim();
222 
223     write!(
224         BufWriter::new(File::create("rust/doctests_kernel_generated.rs").unwrap()),
225         r#"//! `kernel` crate documentation tests.
226 
227 const __LOG_PREFIX: &[u8] = b"rust_doctests_kernel\0";
228 
229 {rust_tests}
230 "#
231     )
232     .unwrap();
233 
234     write!(
235         BufWriter::new(File::create("rust/doctests_kernel_generated_kunit.c").unwrap()),
236         r#"/*
237  * `kernel` crate documentation tests.
238  */
239 
240 #include <kunit/test.h>
241 
242 {c_test_declarations}
243 
244 static struct kunit_case test_cases[] = {{
245     {c_test_cases}
246     {{ }}
247 }};
248 
249 static struct kunit_suite test_suite = {{
250     .name = "rust_doctests_kernel",
251     .test_cases = test_cases,
252 }};
253 
254 kunit_test_suite(test_suite);
255 
256 MODULE_LICENSE("GPL");
257 "#
258     )
259     .unwrap();
260 }
261