1 // SPDX-License-Identifier: GPL-2.0
2
3 //! Test builder for `rustdoc`-generated tests.
4 //!
5 //! This script is a hack to extract the test from `rustdoc`'s output. Ideally, `rustdoc` would
6 //! have an option to generate this information instead, e.g. as JSON output.
7 //!
8 //! The `rustdoc`-generated test names look like `{file}_{line}_{number}`, e.g.
9 //! `...path_rust_kernel_sync_arc_rs_42_0`. `number` is the "test number", needed in cases like
10 //! a macro that expands into items with doctests is invoked several times within the same line.
11 //!
12 //! However, since these names are used for bisection in CI, the line number makes it not stable
13 //! at all. In the future, we would like `rustdoc` to give us the Rust item path associated with
14 //! the test, plus a "test number" (for cases with several examples per item) and generate a name
15 //! from that. For the moment, we generate ourselves a new name, `{file}_{number}` instead, in
16 //! the `gen` script (done there since we need to be aware of all the tests in a given file).
17
18 use std::io::Read;
19
20 fn main() {
21 let mut stdin = std::io::stdin().lock();
22 let mut body = String::new();
23 stdin.read_to_string(&mut body).unwrap();
24
25 // Find the generated function name looking for the inner function inside `main()`.
26 //
27 // The line we are looking for looks like one of the following:
28 //
29 // ```
30 // fn main() { #[allow(non_snake_case)] fn _doctest_main_rust_kernel_file_rs_28_0() {
31 // fn main() { #[allow(non_snake_case)] fn _doctest_main_rust_kernel_file_rs_37_0() -> Result<(), impl core::fmt::Debug> {
32 // ```
33 //
34 // It should be unlikely that doctest code matches such lines (when code is formatted properly).
35 let rustdoc_function_name = body
36 .lines()
37 .find_map(|line| {
38 Some(
39 line.split_once("fn main() {")?
40 .1
41 .split_once("fn ")?
42 .1
43 .split_once("()")?
44 .0,
45 )
46 .filter(|x| x.chars().all(|c| c.is_alphanumeric() || c == '_'))
47 })
48 .expect("No test function found in `rustdoc`'s output.");
49
50 // Qualify `Result` to avoid the collision with our own `Result` coming from the prelude.
51 let body = body.replace(
52 &format!("{rustdoc_function_name}() -> Result<(), impl core::fmt::Debug> {{"),
53 &format!("{rustdoc_function_name}() -> core::result::Result<(), impl core::fmt::Debug> {{"),
54 );
55
56 // For tests that get generated with `Result`, like above, `rustdoc` generates an `unwrap()` on
57 // the return value to check there were no returned errors. Instead, we use our assert macro
58 // since we want to just fail the test, not panic the kernel.
59 //
60 // We save the result in a variable so that the failed assertion message looks nicer.
61 let body = body.replace(
62 &format!("}} {rustdoc_function_name}().unwrap() }}"),
63 &format!("}} let test_return_value = {rustdoc_function_name}(); assert!(test_return_value.is_ok()); }}"),
64 );
65
66 // Figure out a smaller test name based on the generated function name.
67 let name = rustdoc_function_name.split_once("_rust_kernel_").unwrap().1;
68
69 let path = format!("rust/test/doctests/kernel/{name}");
70
71 std::fs::write(path, body.as_bytes()).unwrap();
72 }
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