Automatically install toolchain from `rust-toolchain.toml`

[npmccallum]

Do the checklist before filing an issue:

• [x] Is this related to the actions-rs Actions? If you think it's a problem related to Github Actions in general, use GitHub Community forum instead: https://github.community
• [x] You've read the Contributing section about feature requests: https://github.com/actions-rs/.github/blob/master/CONTRIBUTING.md#feature-requests
• [ ] Is this something you can debug and fix? Send a pull request! Bug fixes and documentation fixes are welcome.

Motivation

Cargo now offers the rust-toolchain.toml file which allows a project to specify what toolchain details it needs. Currently, actions-rs requires you to set up two actions:

• actions-rs/toolchain@v1 - install the toolchain things you need
• actions-rs/cargo@v1 - run cargo (i.e. build)

Instead, the actions-rs/cargo@v1 action could detect if no toolchain was manually specified in the actions yml. If not, it should read rust-toolchain.toml and install all the required stuff automatically.

Workflow example

rust-toolchain.toml:

[toolchain]
channel = "nightly-2021-09-30"
targets = ["x86_64-unknown-linux-gnu", "x86_64-unknown-linux-musl"]
profile = "minimal"

.github/workflows/test.yml:

on: [push]

name: CI

jobs:
  build_and_test:
    name: Rust project
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: actions-rs/cargo@v1
        with:
          command: build
          args: --release --all-features

Notice the lack of any reference to actions-rs/toolchain@v1. Instead, actions-rs/cargo@v1 will install everything required as specified in the rust-toolchain.toml file.

Additional context

https://rust-lang.github.io/rustup/overrides.html#the-toolchain-file

[npmccallum]

Alternatively, you could do:

on: [push]

name: CI

jobs:
  build_and_test:
    name: Rust project
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: actions-rs/toolchain@v1
      - uses: actions-rs/cargo@v1
        with:
          command: build
          args: --release --all-features

Where the toolchain action gathers all the details from the rust-toolchain.toml file.

[maroider]

Where the toolchain action gathers all the details from the rust-toolchain.toml file.

This doesn't work at all for me. The action just fails with toolchain input was not given and repository does not have a rust-toolchain file.

.github/workflows/release.yml

name: Release
on:
  push:
    tags:
      - "v*.*.*"

jobs:
  build:
    runs-on: windows-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v2
      - name: Setup Rust toolchain
        uses: actions-rs/toolchain@v1
      - name: Build release binary
        uses: actions-rs/cargo@v1
        with:
          command: build
          args: --release
      - name: Release
        uses: softprops/action-gh-release@v1
        with:
          files: target/release/fstlg.exe

rust-toolchain.toml

[toolchain]
channel = "nightly-2022-08-14"

[zicklag]

@maroider I believe that @npmccallum is saying that would be an alternative way that the action could behave, not how it behaves currently.

---

For what it's worth, either of the options above for potential behaviors would be quite useful to me.

[dsherret]

I created a new minimal action specifically for this for anyone who needs it: https://github.com/dsherret/rust-toolchain-file