Re: [RFC PATCH 08/11] rust: build: establish a baseline of lints across all crates

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/13/24 08:14, Junjie Mao wrote:
> 
> Paolo Bonzini <pbonzini@redhat.com> writes:
> 
>> Many lints that default to allow can be helpful in detecting bugs or
>> keeping the code style homogeneous.  Add them liberally, though perhaps
>> not as liberally as in hw/char/pl011/src/lib.rs.  In particular, enabling
>> entire groups can be problematic because of bitrot when new links are
>> added in the future.
>>
>> For Clippy, this is actually a feature that is only present in Cargo
>> 1.74.0 but, since we are not using Cargo to *build* QEMU, only developers
>> will need a new-enough cargo and only to run tools such as clippy.
>> The requirement does not apply to distros that are building QEMU.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>>   rust/Cargo.toml               | 66 +++++++++++++++++++++++++++++++++++
>>   rust/hw/char/pl011/src/lib.rs | 18 ++--------
>>   rust/qemu-api/src/bindings.rs |  6 ++--
>>   3 files changed, 71 insertions(+), 19 deletions(-)
>>
>> diff --git a/rust/Cargo.toml b/rust/Cargo.toml
>> index 1ff8f5c2781..43cca33a8d8 100644
>> --- a/rust/Cargo.toml
>> +++ b/rust/Cargo.toml
>> @@ -19,3 +19,69 @@ unknown_lints = "allow"
>>
>>   # Prohibit code that is forbidden in Rust 2024
>>   unsafe_op_in_unsafe_fn = "deny"
>> +
> [snip]
>> +
>> +# nice to have, but cannot be enabled yet
>> +#wildcard_imports = "deny"
>> +
>> +# these may have false positives
>> +#option_if_let_else = "deny"
>> +cognitive_complexity = "deny"
> 
> Just to confirm, CC <= 25 is to be enforced for all methods, right?

I wanted an opinion on that.  option_if_let_else has been more of a pain 
than a benefit, sometimes it suggests code that is worse or does not 
even compile.

So far I've never had any cognitive_complexity error show up, but pl011 
used it so I have kept it in Cargo.toml.  If we start having too many 
#[allow()] for cognitive_complexity we can remove it; for many of the 
others, instead, we might even change deny to forbid.

Paolo