Date:   Tue, 18 Jul 2023 16:38:28 +0800
From:   David Gow <davidgow@...gle.com>
To:     Miguel Ojeda <ojeda@...nel.org>
Cc:     Brendan Higgins <brendan.higgins@...ux.dev>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        Alice Ryhl <aliceryhl@...gle.com>,
        Andreas Hindborg <nmi@...aspace.dk>,
        kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v2 0/7] KUnit integration for Rust doctests

On Tue, 18 Jul 2023 at 13:28, Miguel Ojeda <ojeda@...nel.org> wrote:
>
> v1: https://lore.kernel.org/rust-for-linux/20230614180837.630180-1-ojeda@kernel.org/
> v2:
>
>   - Rebased on top of v6.5-rc1, which requires a change from
>     `kunit_do_failed_assertion` to `__kunit_do_failed_assertion` (since
>     the former became a macro) and the addition of a call to
>     `__kunit_abort` (since previously the call was done by the old
>     function which we cannot use anymore since it is a macro). (David)
>
>   - Added prerequisite patch to KUnit header to include `stddef.h` to
>     support the `KUNIT=y` case. (Reported by Boqun)
>
>   - Added comment on the purpose of `trait FromErrno`. (Martin asked
>     about it)
>
>   - Simplify code to use `std::fs::write` instead of `write!`, which
>     improves code size too. (Suggested by Alice)
>
>   - Fix copy-paste type in docs from "error" to "info" and, to make it
>     proper English, copy the `printk` docs style, i.e. from "info"
>     to "info-level message" -- and same for the "error" one. (Miguel)
>
>   - Swap `FILE` and `LINE` `static`s to keep the same order as done
>     elsewhere. (Miguel)
>
>   - Rename config option from `RUST_KERNEL_KUNIT_TEST` to
>     `RUST_KERNEL_DOCTESTS` (and update its title), so that we can use
>     the former for the "normal" (i.e. non-doctests, e.g. `#[test]` ones)
>     tests in the future. (David)
>
>   - Follow the syntax proposed for declaring test metadata in the KTAP
>     v2 spec, which may also get used for the KUnit test attributes API.
>
>     Thus, instead of "# Doctest from line {line}", use
>     "# {test_name}.location: {file}.{line}", which ideally will allow to
>     migrate to a KUnit attribute later.
>
>     This is done in all cases, i.e. when the tests succeeds, because
>     it may be useful for users running KUnit manually, or when passing
>     `--raw_output` to `kunit.py`. (David)
>
>     David: I used "location" instead of your suggested "line" alone, in
>     order to have both in a single line, which looked nice and closer to
>     the "ASSERTION FAILURE" case/line, since now we do have the original
>     file (please see below).

I like "location" better, personally. The attributes work is still
ongoing, and while there's some benefit to having "file" and "line"
separate (it could potentially simplify some implementation on the C
side), we'll cross that bridge when we come to it.

>
>   - Figure out the original line. This is done by deploying an anchor
>     so that the difference in lines between the beginning of the test
>     and the assert, in the generated file, can be computed. Then, we
>     offset the line number of the original test, which is given by
>     `rustdoc`. (developed by Boqun)
>
>   - Figure out the original file. This is done by walking the
>     filesystem, checking directory prefixes to reduce the amount of
>     combinations to check, and it is only done once per file (rather
>     than per test).
>
>     Ambiguities are detected and reported. It does limit the filenames
>     (module names) we can use, but it is unlikely we will hit it soon
>     and this should be temporary anyway until `rustdoc` provides us
>     with the real path. (Miguel)
>
>     Tested with both in-tree and `O=` builds, but I would appreciate
>     extra testing on this one, including via the `kunit.py` script.
>

This seems to be working well on the existing cases under kunit.py
here. I'll continue to play with it, but no worries on my end thus
far.

>   - The three last items combined means that we now see this output even
>     for successful cases:
>
>         # rust_doctest_kernel_sync_locked_by_rs_0.location: rust/kernel/sync/locked_by.rs:28
>         ok 53 rust_doctest_kernel_sync_locked_by_rs_0
>
>     Which basically gives the user all the information they need to go
>     back to the source code of the doctest, while keeping them fairly
>     stable for bisection, and while avoiding to require users to write
>     test names manually. (David + Boqun + Miguel)
>
>     David: from what I saw in v2 of the RFC for the test attributes API,
>     the syntax still contains the test name when it is not a suite, so
>     I followed that, but if you prefer to omit it, please feel free to
>     do so (for me either way it is fine, and if this is the expected
>     attribute syntax, I guess it is worth to follow it to make migration
>     easier later on):
>
>         # location: rust/kernel/sync/locked_by.rs:28
>         ok 53 rust_doctest_kernel_sync_locked_by_rs_0

Thanks: while we're still arguing a bit about exactly what the format
of these will look like in the KUnit/KTAP attributes spec/patches,
what you've used matches what we've been proposing so far.

Let's stick with <test name>.location for now, and change it if needed
when the attributes spec is finalised.

>
>   - Collected `Reviewed-by`s and `Tested-by`s, except for the main
>     commit due to the substantial changes.
>
> Miguel Ojeda (7):
>   kunit: test-bug.h: include `stddef.h` for `NULL`
>   rust: init: make doctests compilable/testable
>   rust: str: make doctests compilable/testable
>   rust: sync: make doctests compilable/testable
>   rust: types: make doctests compilable/testable
>   rust: support running Rust documentation tests as KUnit ones
>   MAINTAINERS: add Rust KUnit files to the KUnit entry

These are all (still) looking pretty good to me. If there are no
objections, I'd like to take these into kselftest/kunit as-is and if
we need to change anything (e.g. for consistency with attributes when
they land), do that as a follow-up.

Thanks again, Miguel, for all the work getting this going!

Cheers,
-- David

>
>  MAINTAINERS                       |   2 +
>  include/kunit/test-bug.h          |   2 +
>  lib/Kconfig.debug                 |  13 ++
>  rust/.gitignore                   |   2 +
>  rust/Makefile                     |  29 ++++
>  rust/bindings/bindings_helper.h   |   1 +
>  rust/helpers.c                    |   7 +
>  rust/kernel/init.rs               |  26 +--
>  rust/kernel/kunit.rs              | 163 +++++++++++++++++++
>  rust/kernel/lib.rs                |   2 +
>  rust/kernel/str.rs                |   4 +-
>  rust/kernel/sync/arc.rs           |   9 +-
>  rust/kernel/sync/lock/mutex.rs    |   1 +
>  rust/kernel/sync/lock/spinlock.rs |   1 +
>  rust/kernel/types.rs              |   6 +-
>  scripts/.gitignore                |   2 +
>  scripts/Makefile                  |   4 +
>  scripts/rustdoc_test_builder.rs   |  72 +++++++++
>  scripts/rustdoc_test_gen.rs       | 260 ++++++++++++++++++++++++++++++
>  19 files changed, 591 insertions(+), 15 deletions(-)
>  create mode 100644 rust/kernel/kunit.rs
>  create mode 100644 scripts/rustdoc_test_builder.rs
>  create mode 100644 scripts/rustdoc_test_gen.rs
>
>
> base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5
> --
> 2.41.0
>
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