"cargo check" or similar to run all phases prior to trans

[tomjakubowski]

During the edit-compile cycle it's often annoying to have to wait for trans to finish before moving on to the next edits. I propose a new subcommand, cargo check, that runs only the parsing, expansion, and checking/analysis phases where possible when building the project.

The implementation would be just like cargo build, but passing --no-trans to rustc when building the leaves of the crate dependency graph. A --lib option, like on cargo build, would only build the project's lib target if it has one.

[Gankra]

👍 This would be super great.

[iopq]

I compile mostly to check program correctness. I only run the tests when I am about to push my changes.

Now, my stuff is toy programs, but if it ever got to the point that I wrote a larger example that took longer to compile this would be great.

[alexcrichton]

cc #595, this may just be cargo rustc --no-trans

[Valloric]

@alexcrichton cargo rustc --no-trans is neither very user-friendly nor easily discoverable. cargo check sounds like a really solid idea.

[norcalli]

rustc --no-trans main.rs doesn't work for me, is it supposed to?

[DanielKeep]

It's cargo rustc -- -Z no-trans, and apparently, even if the build succeeds, the cargo rustc command itself fails and reports "An unknown error occurred", with an exit status of 101.

So it's not quite the same thing. :P

[rsolomo]

I've taken a pass at creating a cargo check as an external subcommand here: https://github.com/rsolomo/cargo-check

[munael]

Would an integrated cargo check be just an alias for -Zno-trans? I don't know either way, genuinely asking.

[MarkSwanson]

$ cargo rustc -- -Z no-trans
extra arguments to rustc can only be passed to one target, consider filtering
the package by passing e.g. --lib or --bin NAME to specify a single target

(cargo-check has the same problem)

In my Cargo.toml I have:
[[bin]]
name = "runme"
path = "src/bin/runme.rs"

[lib]
name = "my_lib"
path = "src/lib.rs"

I'd like them both to be compiled with -Zno-trans (remove the restriction of a single target).

Reason: I do not want to manually type different commands to compile everything with -Zno-trans; it's just too much work. In vim I'd just like to ":mak" - which works fine until I add -Zno-trans :-(

Thanks!

[alexcrichton]

This now exists! It should also be quite easy to install via cargo install.

[Valloric]

Why does the user have to install it separately? It's neither easily discoverable nor friendly to newbies.

[arthurprs]

@Valloric I share the opinion.

Even when incremental compilation lands llvm will probably always take a big chunk of compilation time, so I see no reason not to incorporate this feature in cargo itself.

[Valloric]

@arthurprs Exactly! This is a trivial command to add and cargo should have it by default so that it shows up in cargo help, which every single newbie will run. It should then be recommended in the Rust guide to further increase the chances that newbies pick up on it.

It would lead to a massive quality-of-life improvement for everyday Rust development. It's such an easy, low-cost win that I can't fathom why the core devs aren't falling over themselves to implement it.