Add option to `cargo check` to check all targets, including test code

[bruno-medeiros]

Basically more or less the check version of cargo test --no-run

[jonhoo]

See also discussion following #3296 (comment) for motivation

[alexcrichton]

IIRC Cargo does support cargo test --test foo to check a particular test, but I think we need two more additions here:

• Like with cargo rustc, --profile test. This'd allow cargo check --lib --profile test to test compiling the library with tests
• Support cargo check --tests to just check all tests, etc. Also things like cargo check --bins, cargo check --examples, etc.

[bruno-medeiros]

Support cargo check --tests to just check all tests, etc. Also things like cargo check --bins, cargo check --examples, etc.

Actually, to be more precise: this should an option that checks all targets (lib, bin, test, examples, doc). The full-build equivalent (cargo test --no-run) does that already, it build all targets - not just test targets but bin, doc, examples, too. (dunno if that behaviour was the original intention, but it's good that it does that)

[alexcrichton]

Ah yeah that makes sense to me to have some form of as well. We may be able to emulate that with cargo check --all or something like that.

[crumblingstatue]

Don't know about checking tests specifically, but cargo build has the --all option to build all targets in a workspace. It feels unsymmetrical that cargo check doesn't have this option.

[alexcrichton]

I've added check --all in #3731, but it doesn't handle tests (e.g. the default current behavior), so I'm going to clleave this open.

[jonhoo]

@alexcrichton any idea when --all will get support for running test (or when we'll see --test)? It'd be really nice to have in the vim syntax checker (see neomake/neomake#843 (comment))

[ehuss]

Just a warning for whoever works on this, when the test harness is included (rustc --test), it disables the missing_docs lint. Also, it disables the "main function not found" error for binaries. I'm not sure how it will be implemented in the context of cargo check, but something to watch out for.