Cargo build unit count exposure

[notchapplez]

Problem

Hey! I currently have a project running that requires reading the cargo build unit count (the one that is shown in the bottom bar when building). While coding, I noticed there was no reliable way to read the build unit count, which could be probably used for a lot of stuff.

Proposed Solution

I wish to have the build unit count be exposed using arguments so it is easier for developers to read the count and use it in their project as I have been struggling for the last 5 hours with getting an exact count

Notes

No response

[notchapplez]

This would be nice on the stable toolchain

[weihanglo]

cargo build unit count (the one that is shown in the bottom bar when building).

Could you give the console output examples of what it is? The progress bar or the final summary status?

which could be probably used for a lot of stuff.

Do you mind elaborating the exact use case and workflow you have? That would be easier to design and discuss without guessing.

[notchapplez]

So I am currently developing unin-rs which is a universal installer that wraps lots of installing/compilation tools as a toolbox kind of. Just so that daily users don't feel like the process is stuck, I wanted to implement a progress bar using indicatif at the bottom of the screen/terminal. I would need the build unit count for that so I could tick the bar once when the compilation event for that unit finishes in the stdout json logs. I have another solution for now, but this could still get useful for me.

[epage]

A potential rearchitecture of cargo fix has the same need, see crate-ci/cargo-fixit#68

My personal hope is that as we work on structured logging in Cargo (which already includes all of the build units before the build so you can count them), we will also emit those as part of the --message-format=json and can leverage them for building UIs on top of Cargo.

[notchapplez]

Okay, should I close the issue?

[weihanglo]

The tracking issue of structured log is #15844, and the label https://github.com/rust-lang/cargo/issues?q=label%3AZ-build-analysis.