All dependencies recompiled if there is an error during "cargo install <crate>"

[vezaynk]

I am running cargo install letsencrypt-rs and every time there is an issue with a dependency (Needed to install make, etc), the process was killed and when I tried again it would recompile every single one of the dependencies.

This is bad because the compiled dependencies should be instead reused as it takes a ton of time, much more so when there is seemingly a hundred dependencies.

There's probably a more minimal way to reproduce it but one way is to take a system without make, run cargo install letsencrypt-rs, after a certain dependency it will fail and make you restart all over again.

[sputnick1124]

A reasonable workaround for this is to set the environment variable CARGO_TARGET_DIR to someplace you'd like to store the intermediate artifacts. This will tell cargo to cache all of the successfully built products in said directory and reuse them on subsequent builds.

If the CARGO_TARGET_DIR is not set, when you run cargo install <doomed-to-fail>, cargo will nonetheless report something like:

error: failed to compile `doomed-to-fail v0.1`, intermediate artifacts can be found at '/some/tmp/directory'

After fixing your dependencies, you can run CARGO_TARGET_DIR=/some/tmp/directory cargo install hopefully-this-works and cargo will find the intermediates from the previously failed attempt.

Tested with version 1.31.0. HTH.

[weihanglo]

sputnick1124 is pretty much correct I believe. To improve, we could tell people do what sputnick1124 has taught in the error message, like:

error: failed to compile `doomed-to-fail v0.1`, intermediate artifacts can be found at '/some/tmp/directory'
    To reuse those artifacts, set the environment variable `CARGO_TARGET_DIR` to that path.

There code lives here:

cargo/src/cargo/ops/cargo_install.rs

Lines 321 to 326 in 64fb38c

	format!(
	"failed to compile `{}`, intermediate artifacts can be \
	found at `{}`",
	self.pkg,
	self.ws.target_dir().display()
	)