Profile not respected when rust-toolchain file is present

[Robin Lambertz]

Description

When a rust-toolchain file is present, the first invocation of rust-toolchain will cause it to download the specified toolchain before executing the command. Toolchain starts by issuing a rustup show, which will pull the entire toolchain (with docs and all) before it has a chance to set the profile.

Workflow code

https://github.com/MegatonHammer/linkle/blob/master/.github/workflows/ci.yml#L34

Notice that at the root of the repo, linkle has a rust-toolchain file specifying the exact rust version in use.

Action output

2020-04-16T22:34:36.0589784Z ##[group]Run actions-rs/toolchain@v1
2020-04-16T22:34:36.0589995Z with:
2020-04-16T22:34:36.0590096Z   profile: minimal
2020-04-16T22:34:36.0590189Z   default: false
2020-04-16T22:34:36.0590263Z   override: false
2020-04-16T22:34:36.0590353Z ##[endgroup]
2020-04-16T22:34:36.5867846Z [command]C:\Rust\.cargo\bin\rustup.exe show
2020-04-16T22:34:37.2864063Z Default host: x86_64-pc-windows-msvc
2020-04-16T22:34:37.2865945Z rustup home:  C:\Users\runneradmin\.rustup
2020-04-16T22:34:37.2866332Z 
2020-04-16T22:34:37.3284425Z info: syncing channel updates for '1.42.0-x86_64-pc-windows-msvc'
2020-04-16T22:34:38.2496283Z info: latest update on 2020-03-12, rust version 1.42.0 (b8cedc004 2020-03-09)
2020-04-16T22:34:38.2502795Z info: downloading component 'cargo'
2020-04-16T22:34:38.5366370Z info: downloading component 'clippy'
2020-04-16T22:34:38.7433766Z info: downloading component 'rust-docs'
2020-04-16T22:34:39.3043959Z info: downloading component 'rust-std'
2020-04-16T22:34:40.5843526Z info: downloading component 'rustc'
2020-04-16T22:34:45.2767614Z info: downloading component 'rustfmt'
2020-04-16T22:34:45.5245996Z info: installing component 'cargo'
2020-04-16T22:34:46.7297457Z info: installing component 'clippy'
2020-04-16T22:34:47.1278658Z info: installing component 'rust-docs'
2020-04-16T22:35:24.1909816Z info: installing component 'rust-std'
2020-04-16T22:35:25.5992336Z info: installing component 'rustc'
2020-04-16T22:35:32.3399201Z info: installing component 'rustfmt'
2020-04-16T22:35:32.8065802Z 1.42.0-x86_64-pc-windows-msvc (overridden by '\\?\D:\a\linkle\linkle\rust-toolchain')
2020-04-16T22:35:33.2786796Z rustc 1.42.0 (b8cedc004 2020-03-09)
2020-04-16T22:35:33.2978065Z [command]C:\Rust\.cargo\bin\rustup.exe -V
2020-04-16T22:35:33.3104072Z rustup 1.21.1 (7832b2ebe 2019-12-20)
2020-04-16T22:35:33.3138148Z Installed rustup 1.21.1 support profiles
2020-04-16T22:35:33.3142655Z [command]C:\Rust\.cargo\bin\rustup.exe set profile minimal
2020-04-16T22:35:33.6254726Z info: profile set to 'minimal'
2020-04-16T22:35:33.6292333Z [command]C:\Rust\.cargo\bin\rustup.exe toolchain install 1.42.0
2020-04-16T22:35:33.7250173Z info: syncing channel updates for '1.42.0-x86_64-pc-windows-msvc'
2020-04-16T22:35:33.8301865Z 
2020-04-16T22:35:33.8497081Z   1.42.0-x86_64-pc-windows-msvc unchanged - rustc 1.42.0 (b8cedc004 2020-03-09)
2020-04-16T22:35:33.8497456Z 
2020-04-16T22:35:33.8507677Z info: checking for self-updates
2020-04-16T22:35:33.8919155Z ##[group]Gathering installed versions
2020-04-16T22:35:33.9179529Z [command]C:\Rust\.cargo\bin\rustc.exe -V
2020-04-16T22:35:33.9477354Z rustc 1.42.0 (b8cedc004 2020-03-09)
2020-04-16T22:35:33.9826013Z [command]C:\Rust\.cargo\bin\cargo.exe -V
2020-04-16T22:35:34.0146277Z cargo 1.42.0 (86334295e 2020-01-31)
2020-04-16T22:35:34.0466135Z [command]C:\Rust\.cargo\bin\rustup.exe -V
2020-04-16T22:35:34.0587717Z rustup 1.21.1 (7832b2ebe 2019-12-20)
2020-04-16T22:35:34.0613780Z ##[endgroup]

Expected behavior

I expect the rustup profile to be set before it starts downloading components, to avoid accidentally downloading the rust-docs. Perhaps it should cd into a temporary folder in order to set the profile without accidentally triggering an automatic toolchain download?