This GitHub Action installs Rust toolchain.

Optionally it can set installed toolchain as a default and as an override for current directory.

on: [push]

name: build

jobs:
  check:
    name: Rust project
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@master
      - name: Install latest nightly
        uses: actions-rs/toolchain@v1
        with:
            toolchain: nightly
            override: true

      # `cargo check` command here will use installed `nightly`
      # as it set as an "override" for current directory

      - name: Run cargo check
        uses: actions-rs/cargo@v1
        with:
          command: check

See additional recipes here.

This Action supports rustup profiles, which are can be used to speed up the workflow execution by installing the minimally required set of components, for example:

- name: Install minimal nightly
  uses: actions-rs/toolchain@v1
  with:
    profile: minimal
    toolchain: nightly

This Action will automatically run rustup self update if profile input is set and the installed rustup version does not supports them.

In order to provide backwards compatibility for v1 version, there is no value for profile input set by default, which means that the default profile is used by rustup (and that includes rust-docs, clippy and rustfmt).
You may want to consider using profile: minimal to speed up toolchain installation.

This Action supports rustup components too, and in combination with the profiles input it allows to install only the needed components:

- name: Install minimal stable with clippy and rustfmt
  uses: actions-rs/toolchain@v1
  with:
    profile: minimal
    toolchain: nightly
    components: rustfmt, clippy

As an extra perk, rustup >= 1.20.0 is able to find the most recent nightly toolchain with the requested components available; next example is utilizing this feature to install the minimal set of nightly toolchain components with the rustfmt and clippy extras:

- name: Install minimal nightly with clippy and rustfmt
  uses: actions-rs/toolchain@v1
  with:
    profile: minimal
    toolchain: nightly
    components: rustfmt, clippy

Same to the profile input, if the installed rustup does not supports "components", it will be automatically upgraded by this Action.

As rustup is not installed by default for macOS environments at the moment (2019-09-13), this Action will try its best to install it before any other operations.