rust-lang/rust-clippy

`use_debug` lint should not trigger on `debug!()` log macro calls

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#2132 opened on Oct 12, 2017

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 (7 comments) (1 reaction) (0 assignees)Rust (10,406 stars) (1,391 forks)batch import
C-enhancementT-middlegood first issue

Description

Example use-case:

#![cfg_attr(feature = "cargo-clippy", warn(use_debug))]

#[macro_use]
extern crate log;

pub fn euclid_steps(mut x: u64, mut y: u64) -> Vec<u64> {
    debug!("x = {}, y = {}", x, y);

    let mut steps = vec![];

    loop {
        let tmp = x % y;

        if tmp == 0 {
            debug!("Steps performed in Euclidean algorithm: {:?}", steps);
            return steps;
        }

        steps.push(tmp);
        x = y;
        y = tmp;
    }
}

Placing #![cfg_attr(feature = "cargo-clippy", allow(use_debug))] before each debug!() usage seems tedious to me when there are several dozens of them; and turning it off (even if locally) defeats the purpose of the lint.

Contributor guide

Tech stack
rust
Domain
toolingdeveloper experience
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Rust macrosclippy lint frameworklog crate
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Investigate the `use debug` lint implementation in the clippy codebase (likely in `clippy lints/src/use debug.rs`). Understand how it currently triggers on `debug!()` calls. Consider adding an exception for the `debug!` macro from the `log` crate, possibly by checking the macro's path or using a whitelist. Review the existing discussion in the issue comments for any proposed solutions.