Cargo check should allow disabling warnings

[Storyyeller]

There are a lot of compiler warnings that are noisy and useless during development, such as dead_code. Unfortunately, cargo check does not have any way of disabling these warnings. There needs to be a way to disable specific warnigns when running cargo check.

So far, the only workaround I've found is export RUSTFLAGS='-A dead_code', which is ugly and undiscoverable, and you have to remember to undo it when you are ready for release.

[alexcrichton]

cc @nrc @jonathandturner, opinions on this?

[nrc]

I would not object to having this. Its not something that I've noticed being super-painful though.

[sophiajt]

Ditto. WFM

[chriskrycho]

I'll give an example of where I'd find it useful: I'm building up a library and I have a bunch of code I know I'll be using, because I've written them to use elsewhere in the library. But I get dead-code warnings constantly because I haven't written those implementations yet, and it's just noise while I'm working on fixing a broken test, or on seeing actual build errors elsewhere in the library, etc.

[sfackler]

On the other side of things, I leave warnings as warnings when working on a crate, but then want to turn them into errors on CI. cargo build -D warnings is a bit nicer than env RUSTFLAGS="-D warnings" cargo build IMO. It's way easer to see them pop up in cargo build --help than knowing about RUSTFLAGS. Even if you did know about it, I don't want to forbid warnings on dependencies and didn't realize that cargo's lint capping would still work with RUSTFLAGS for a while.

[nikomatsakis]

I strongly want this too. I came to the repo looking to file an issue requesting cargo build -A warnings, but I think what I really want is for both cargo check and cargo build to support -A and -D. I think I would not want to change the defaults for either of them.

[nrc]

If we do anything, we should do it for both check and build, and I think we should not change the defaults. But I think it would be nice to have the option (I've recently been doing more experimental work, and I think I'd like this).

[pronebird]

That would be awesome for cargo build too. I am seeing lots of warnings recently due to some changes in doc comments. This totally clogs the output and there is no way to find actual errors without going through the 20 screens of warnings.

[brokenthorn]

Where I find it annoying is when the output is not colored (ie. IDE terminal doesn't support it) and I just want to check and fix errors quickly when making incremental changes to code or when I'm just testing or playing around, like in a "test-some-posibility" branch. It's a bit harder on my eyes to stop at the first error when warnings are printed first. I have to traverse all the warnings first.

[najamelan]

How about just putting this in your crate during development:

#![ allow( dead_code, unused_imports ) ]

[alexkreidler]

I also saw this: cargo test 2>/dev/null, which might work similarly for cargo bulid.

Source: https://users.rust-lang.org/t/suppress-warnings-from-the-cargo-command/10536/6