Clippy doesn't take into account configuration overrides given through cargo --config CLI

[anlavandier]

Summary

Clippy will not take into account cargo --config CLI arguments. This leads to cases where cargo clippy is unable to resolve dependencies when cargo build and cargo check both can.

Reproducer

I built a new empty cargo project and added a single dependency (in my case itertools but it doesn't matter) and asked for a feature that doesn't exist in the version on crates.io. This leads to the following Cargo.toml :

[package]
name = "clippy-bug-test"
version = "0.1.0"
edition = "2024"

[dependencies]
itertools = { version = "0.14", default-features = false, features = ["SomeNewFeature"] }

Naturally this doesn't compile.

Now to simulate having made a fork of itertools that includes the aforementioned feature (SomeNewFeature), I simply created another empty project in the directory my-itertools, named it itertools and added this single feature. Here's the Cargo.toml:

[package]
name = "itertools"
version = "0.14.0"
edition = "2024"

[features]
SomeNewFeature = []

The crate clippy-bug-test can now be build by using the following command:

~/clippy-bug-test$ cargo --config "patch.crates-io.itertools.path='/path/to/my-itertools'" build

I expected to see this happen:

~/clippy-bug-test$ cargo --config "patch.crates-io.itertools.path='/path/to/my-itertools'" clippy

to work normally, like cargo build and cargo check did.

Instead, this happened:

~/clippy-bug-test$ cargo --config "patch.crates-io.itertools.path='/path/to/my-itertools'" clippy
    Updating crates.io index
error: failed to select a version for `itertools`.
    ... required by package `clippy-bug-test v0.1.0 (/home/tribe/clippy-bug-test)`
versions that meet the requirements `^0.14` are: 0.14.0

the package `clippy-bug-test` depends on `itertools`, with features: `SomeNewFeature` but `itertools` does not have these features.


failed to select a version for `itertools` which could resolve this conflict

Version

rustc 1.86.0 (05f9846f8 2025-03-31)
binary: rustc
commit-hash: 05f9846f893b09a1be1fc8560e33fc3c815cfecb
commit-date: 2025-03-31
host: x86_64-unknown-linux-gnu
release: 1.86.0
LLVM version: 19.1.7

Additional Labels

No response

[anlavandier]

This example looks very contrived and it's not a real problem anyway as puttin the patch either in the Cargo.toml or in .cargo/config.toml. This also happens if the patch is given to cargo as cargo --config some-additionnal-config.toml instead of through key-value pairs.

[Alexendoo]

This would be down to rust-lang/cargo#11031

I believe that cargo clippy --config .. works

[anlavandier]

Thanks. I don't know how my various internet searches didn't lead me to that cargo issue. In any case, Seeing as this isn't directly related to clippy, I'm closing this issue.