Option to show cached error messages on 'cargo build' re-run

[msjyoo]

Hello,

Similar to this issue: http://stackoverflow.com/questions/31125226/it-is-possible-to-always-have-cargo-show-warnings

It would be nice to have an option for cargo to cache and display the build errors and warnings even when no changes are detected. This way, recompilation is not required just to see the last error messages.

[alexcrichton]

This seems like it would require quite a bit of support for a somewhat niche use case, but could perhaps be done one day?

[msjyoo]

I agree that it is a bit of a niche case, but support for it would still be nice :)

[msjyoo]

@alexcrichton A more useful alternative would be an option that displays all the errors, without going through the process of generating a binary. If it's fast enough, it could be run continuously on edits without the overhead of generating a binary every time? (I'm guessing the error-checking and binary compilation steps are separated)

[alexcrichton]

Ah yeah unfortunately the compiler doesn't support doing that, but we've talked about a mode like that in the past!

[carols10cents]

This sounds like it would have to be fixed in rust-lang/rust, so I'm closing!

[BatmanAoD]

I'm not sure why this is considered "niche" usage. Repeatedly attempting to compile one's codebase is a typical use case, and I would say it's pretty common for some files to be compiled successfully before others, causing any warnings from those files to be glossed over in order to focus on the remaining hard errors.

[ehuss]

This has been implemented and is tracked in #6986.