Fix: Run the version detection steps in the selected rust-src-dir directory.

This should enable the version selection even without a default
toolchain installed.

Fixes #74.

.github/dependabot.yml

@@ -8,4 +8,4 @@ updates:
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      interval: "monthly"
+      interval: "weekly"

.github/workflows/autotag-releases.yml

@@ -15,7 +15,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v5
       - name: Get version from tag
         id: tag_name
         run: |

.github/workflows/ci.yml

@@ -1,65 +1,106 @@
-
 name: CI
 
 on:
-  push:
+  push: { branches: [main] }
   pull_request:
   schedule: [cron: "40 1 * * *"]
 
 jobs:
   install:
-    name: Rust ${{matrix.rust}} ${{matrix.os}}
+    name: Rust ${{matrix.rust || '(default)'}} (toolchain-file=${{matrix.write-toolchain-file}}) (${{matrix.os}})
     runs-on: ${{matrix.os}}
     strategy:
       fail-fast: false
+      max-parallel: 5
       matrix:
-        rust: [
-          # Test with toolchain file override
-          "1.60",
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-latest
+        write-toolchain-file:
+          - false
+          - true
+        rust:
+          # use stable toolchain as default
+          - null
+
           # Test that the sparse registry check works.
           # 1.66 and 1.67 don't support stable sparse registry.
-          "1.66",
-          "nightly",
-          "beta",
-          "stable",
-        ]
-        os: [
-          "ubuntu-latest",
-          "windows-latest",
-          "macos-latest",
-        ]
+          - "1.66"
+
+          - "nightly"
+          - "beta"
+          - "stable"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v5
+
       # Test toolchain file support
       - name: Write rust-toolchain.toml
+        if: matrix.write-toolchain-file
+        shell: bash
         run: |
           cat <<EOF >>rust-toolchain.toml
           [toolchain]
-          channel = "nightly-2022-09-10"
+          channel = "nightly-2024-01-10"
           components = [ "rustfmt", "rustc-dev" ]
           targets = [ "wasm32-unknown-unknown", "thumbv7m-none-eabi" ]
           profile = "minimal"
           EOF
-        shell: bash
-        if: matrix.rust == '1.60'
 
-      - uses: ./
-        name: Run actions-rust-lang/setup-rust-toolchain ${{matrix.rust}}
-        id: toolchain
+      - id: toolchain
+        name: Run actions-rust-lang/setup-rust-toolchain ${{matrix.rust || 'on toolchain file'}}
+        uses: ./
         with:
           toolchain: ${{matrix.rust}}
+          components: clippy
+
       - name: Check ${{'${{steps.toolchain.outputs.rustc-version}}'}}
         run: echo '${{steps.toolchain.outputs.rustc-version}}'
+
       - name: Check ${{'${{steps.toolchain.outputs.cargo-version}}'}}
         run: echo '${{steps.toolchain.outputs.cargo-version}}'
+
       - name: Check ${{'${{steps.toolchain.outputs.rustup-version}}'}}
         run: echo '${{steps.toolchain.outputs.rustup-version}}'
-      - run: rustc --version && cargo --version
+
+      - name: Check lack of toolchain input or file results in stable
+        if: matrix.write-toolchain-file == false && matrix.rust == null
         shell: bash
+        run: |-
+          rustcv="$(rustc --version)"
+          [[ "$rustcv" != *"nightly"* && "$rustcv" != *"beta"* ]]
+
+      - name: Check toolchain file is being overridden
+        if: matrix.write-toolchain-file
+        shell: bash
+        run: |-
+          rustcv="$(rustc --version)"
+          [[ ! ( "$rustcv" == *"nightly"* && "$rustcv" == *"2024-01-10"* ) ]]
+
+      - shell: bash
+        run: rustc --version && cargo --version
 
       # Test with creating a small project
       - run: cargo init . --bin --name ci
+
       # Add tiny empty crate.
       # This checks that registry access works.
       - run: cargo add serde_as
-      - run: cargo check
+
+      - run: cargo clippy
+
+  cache:
+    name: Cache
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Install Rust
+        uses: ./
+        with:
+          components: clippy
+          cache: true
+          cache-workspaces: |-
+            ./test-workspace
+
+      - run: cargo clippy --manifest-path=./test-workspace/Cargo.toml

.pre-commit-config.yaml

@@ -0,0 +1,18 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.6.0
+    hooks:
+      - id: check-case-conflict
+      - id: check-executables-have-shebangs
+      - id: check-merge-conflict
+      - id: check-json
+      - id: check-yaml
+      - id: end-of-file-fixer
+      - id: trailing-whitespace
+        args: [--markdown-linebreak-ext=md]
+  - repo: https://github.com/python-jsonschema/check-jsonschema
+    rev: 0.29.2
+    hooks:
+      - id: check-dependabot
+      - id: check-github-actions
+      - id: check-github-workflows

CHANGELOG.md

@@ -7,6 +7,111 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.15.2] - 2025-10-04
+
+* Fix: Run the version detection steps in the selected `rust-src-dir` directory.
+    This should enable the version selection even without a default toolchain installed.
+    Fixes #74.
+
+## [1.15.1] - 2025-09-23
+
+* Update `Swatinem/rust-cache` to v2.8.1
+
+## [1.15.0] - 2025-09-14
+
+* Add support for non-root source directory.
+    Accept source code and `rust-toolchain.toml` file in subdirectories of the repository.
+    Adds a new parameter `rust-src-dir` that controls the lookup for toolchain files and sets a default value for the `cache-workspace` input. (#69 by @Kubaryt)
+
+## [1.14.1] - 2025-08-28
+
+* Pin `Swatinem/rust-cache` action to a full commit SHA (#68 by @JohnTitor)
+
+## [1.14.0] - 2025-08-23
+
+* Add new parameters `cache-all-crates` and `cache-workspace-crates` that are propagated to `Swatinem/rust-cache` as `cache-all-crates` and `cache-workspace-crates`
+
+## [1.13.0] - 2025-06-16
+
+* Add new parameter `cache-provider` that is propagated to `Swatinem/rust-cache` as `cache-provider` (#65 by @mindrunner)
+
+## [1.12.0] - 2025-04-23
+
+* Add support for installing rustup on Windows (#58 by @maennchen)
+    This adds support for using Rust on the GitHub provided Windows ARM runners.
+
+## [1.11.0] - 2025-02-24
+
+* Add new parameter `cache-bin` that is propagated to `Swatinem/rust-cache` as `cache-bin` (#51 by @enkhjile)
+* Add new parameter `cache-shared-key` that is propagated to `Swatinem/rust-cache` as `shared-key` (#52 by @skanehira)
+
+## [1.10.1] - 2024-10-01
+
+* Fix problem matcher for rustfmt output.
+    The format has changed since https://github.com/rust-lang/rustfmt/pull/5971 and now follows the form "filename:line".
+    Thanks to @0xcypher02 for pointing out the problem.
+
+## [1.10.0] - 2024-09-23
+
+* Add new parameter `cache-directories` that is propagated to `Swatinem/rust-cache` (#44 by @pranc1ngpegasus)
+* Add new parameter `cache-key` that is propagated to `Swatinem/rust-cache` as `key` (#41 by @iainlane)
+* Make rustup toolchain installation more robust in light of planned changes https://github.com/rust-lang/rustup/issues/3635 and https://github.com/rust-lang/rustup/pull/3985
+* Allow installing multiple Rust toolchains by specifying multiple versions in the `toolchain` input parameter.
+* Configure the `rustup override` behavior via the new `override` input. (#38)
+
+## [1.9.0] - 2024-06-08
+
+* Add extra argument `cache-on-failure` and forward it to `Swatinem/rust-cache`. (#39 by @samuelhnrq)  
+    Set the default the value to true.
+    This will result in more caching than previously.
+    This helps when large dependencies are compiled only for testing to fail.
+
+## [1.8.0] - 2024-01-13
+
+* Allow specifying subdirectories for cache.
+* Fix toolchain file overriding.
+
+## [1.7.0] - 2024-01-11
+
+* Allow overriding the toolchain file with explicit `toolchain` input. (#26)
+
+## [1.6.0] - 2023-12-04
+
+### Added
+
+* Allow disabling problem matchers (#27)
+    This can be useful when having a matrix of jobs, that produce the same errors.
+
+## [1.5.0] - 2023-05-29
+
+### Added
+
+* Support installing additional components and targets that are not listed in `rust-toolchain` (#14)
+    Before only the items listed in `rust-toolchain` were installed.
+    Now all the items from the toolchain file are installed and then all the `target`s and `components` that are provided as action inputs.
+    This allows installing extra tools only for CI or simplify testing special targets in CI.
+* Allow skipping the creation of a `RUSTFLAGS` environment variable.
+    Cargos logic for rustflags is complicated, and setting the `RUSTFLAGS` environment variable prevents other ways of working.
+    Provide a new `rustflags` input, which controls the environment variable creation.
+    If the value is set to the empty string, then `RUSTFLAGS` is not created.
+
+    Pre-existing `RUSTFLAGS` variables are never modified by this extension.
+
+## [1.4.4] - 2023-03-18
+
+### Fixed
+
+* Use color aware problem matcher.
+    The problem matcher currently runs against the colored terminal output ([Bug 1](https://github.com/actions/runner/issues/2341), [Bug 2](https://github.com/actions/runner/pull/2430)).
+    The previous matcher was not aware of ANSII color codes and did not work.
+
+## [1.4.3] - 2023-02-21
+
+### Fixed
+
+* Executing the action twice for different toolchains now no longer fails around unstable features #12.
+    If multiple toolchains are installed, the "CARGO_REGISTRIES_CRATES_IO_PROTOCOL" can be downgraded to "git" if any of the installed toolchains require it.
+
 ## [1.4.2] - 2023-02-15
 
 ### Fixed

README.md

@@ -6,7 +6,7 @@ Caching for Rust tools and build artifacts is enabled.
 Environment variables are set to optimize the cache hits.
 [Problem Matchers] are provided for build messages (cargo, clippy) and formatting (rustfmt).
 
-The action is heavily inspired by *dtolnay*'s <https://github.com/dtolnay/rust-toolchain> and extends it with further features.
+The action is heavily inspired by _dtolnay_'s <https://github.com/dtolnay/rust-toolchain> and extends it with further features.
 
 ## Example workflow
 
@@ -21,16 +21,16 @@ jobs:
     name: cargo test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v5
       - uses: actions-rust-lang/setup-rust-toolchain@v1
       - run: cargo test --all-features
- 
+
   # Check formatting with rustfmt
   formatting:
     name: cargo fmt
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v5
       # Ensure rustfmt is installed and setup problem matcher
       - uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
@@ -42,23 +42,67 @@ jobs:
 ## Inputs
 
 All inputs are optional.
-If a [toolchain file](https://rust-lang.github.io/rustup/overrides.html#the-toolchain-file) (i.e., `rust-toolchain` or `rust-toolchain.toml`) is found in the root of the repository, it takes precedence.
-All input values are ignored if a toolchain file exists.
+If a [toolchain file](https://rust-lang.github.io/rustup/overrides.html#the-toolchain-file) (i.e., `rust-toolchain` or `rust-toolchain.toml`) is found in the root of the repository and no `toolchain` value is provided, all items specified in the toolchain file will be installed.
+If a `toolchain` value is provided, the toolchain file will be ignored.
+If no `toolchain` value or toolchain file is present, it will default to `stable`.
+First, all items specified in the toolchain file are installed.
+Afterward, the `components` and `target` specified via inputs are installed in addition to the items from the toolchain file.
 
-| Name         | Description                                                                       | Default |
-| ------------ | --------------------------------------------------------------------------------- | ------- |
-| `toolchain`  | Rustup toolchain specifier e.g. `stable`, `nightly`, `1.42.0`.                    | stable  |
-| `target`     | Additional target support to install e.g. `wasm32-unknown-unknown`                |         |
-| `components` | Comma-separated string of additional components to install e.g. `clippy, rustfmt` |         |
-| `cache`      | Automatically configure Rust cache (using `Swatinem/rust-cache`)                  | true    |
+| Name                     | Description                                                                                                                                                                        | Default       |
+| ------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------- |
+| `toolchain`              | Comma-separated list of Rustup toolchain specifier e.g. `stable`, `nightly`, `1.42.0`. The last version is the default.                                                            | stable        |
+| `target`                 | Additional target support to install e.g. `wasm32-unknown-unknown`                                                                                                                 |               |
+| `components`             | Comma-separated string of additional components to install e.g. `clippy, rustfmt`                                                                                                  |               |
+| `cache`                  | Automatically configure Rust cache (using [`Swatinem/rust-cache`])                                                                                                                 | true          |
+| `cache-directories`      | Propagates the value to [`Swatinem/rust-cache`]                                                                                                                                    |               |
+| `cache-workspaces`       | Propagates the value to [`Swatinem/rust-cache`]. Influenced by the value of `rust-src-dir`.                                                                                        |               |
+| `cache-on-failure`       | Propagates the value to [`Swatinem/rust-cache`]                                                                                                                                    | true          |
+| `cache-key`              | Propagates the value to [`Swatinem/rust-cache`] as `key`                                                                                                                           |               |
+| `cache-shared-key`       | Propagates the value to [`Swatinem/rust-cache`] as `shared-key`                                                                                                                    |               |
+| `cache-bin`              | Propagates the value to [`Swatinem/rust-cache`] as `cache-bin`                                                                                                                     | true          |
+| `cache-provider`         | Propagates the value to [`Swatinem/rust-cache`] as `cache-provider`                                                                                                                | 'github'      |
+| `cache-all-crates`       | Propagates the value to [`Swatinem/rust-cache`] as `cache-all-crates`                                                                                                              | false         |
+| `cache-workspace-crates` | Propagates the value to [`Swatinem/rust-cache`] as `cache-workspace-crates`                                                                                                        | false         |
+| `matcher`                | Enable problem matcher to surface build messages and formatting issues                                                                                                             | true          |
+| `rustflags`              | Set the value of `RUSTFLAGS` (set to empty string to avoid overwriting existing flags)                                                                                             | "-D warnings" |
+| `override`               | Setup the last installed toolchain as the default via `rustup override`                                                                                                            | true          |
+| `rust-src-dir`           | Path from root directory to directory with the Rust source directory (if its not in the root of the repository). Sets a default value for `cache-workspaces` that enables caching. |               |
+
+[`Swatinem/rust-cache`]: https://github.com/Swatinem/rust-cache
+
+### RUSTFLAGS
+
+By default, this action sets the `RUSTFLAGS` environment variable to `-D warnings`.
+However, rustflags sources are mutually exclusive, so setting this environment variable omits any configuration through `target.*.rustflags` or `build.rustflags`.
+
+- If `RUSTFLAGS` is already set, no modifications of the variable are made and the original value remains.
+- If `RUSTFLAGS` is unset and the `rustflags` input is empty (i.e., the empty string), then it will remain unset.
+  Use this, if you want to prevent the value from being set because you make use of `target.*.rustflags` or `build.rustflags`.
+- Otherwise, the environment variable `RUSTFLAGS` is set to the content of `rustflags`.
+
+To prevent this from happening, set the `rustflags` input to an empty string, which will
+prevent the action from setting `RUSTFLAGS` at all, keeping any existing preferences.
+
+You can read more rustflags, and their load order, in the [Cargo reference].
 
 ## Outputs
 
-| Name             | Description                               |
-| ---------------- | ----------------------------------------- |
-| `rustc-version`  | Version as reported by `rustc --version`  |
-| `cargo-version`  | Version as reported by `cargo --version`  |
-| `rustup-version` | Version as reported by `rustup --version` |
+| Name             | Description                                 |
+| ---------------- | ------------------------------------------- |
+| `rustc-version`  | Version as reported by `rustc --version`    |
+| `cargo-version`  | Version as reported by `cargo --version`    |
+| `rustup-version` | Version as reported by `rustup --version`   |
+| `cachekey`       | A short hash of the installed rustc version |
+
+## Dependencies
+
+The action works best on the GitHub-hosted runners, but can work on self-hosted ones too, provided the necessary dependencies are available.
+PRs to add support for more environments are welcome.
+
+- bash 5
+- brew (macOS only)
+- rustup or curl
+- using other node actions
 
 ## License
 
@@ -67,3 +111,4 @@ License].
 
 [MIT License]: LICENSE
 [Problem Matchers]: https://github.com/actions/toolkit/blob/main/docs/problem-matchers.md
+[Cargo reference]: https://doc.rust-lang.org/cargo/reference/config.html?highlight=unknown#buildrustflags

action.yml

@@ -13,9 +13,8 @@ branding:
 # The action is heavily inspired by https://github.com/dtolnay/rust-toolchain
 inputs:
   toolchain:
-    description: "Rust toolchain specification -- see https://rust-lang.github.io/rustup/concepts/toolchains.html#toolchain-specification"
+    description: "Comma-separated list of Rust toolchain specifications. Last version becomes the default. -- see https://rust-lang.github.io/rustup/concepts/toolchains.html#toolchain-specification"
     required: false
-    default: "stable"
   target:
     description: "Target triple to install for this toolchain"
     required: false
@@ -26,6 +25,53 @@ inputs:
     description: "Automatically configure Rust cache"
     required: false
     default: "true"
+  cache-workspaces:
+    description: "Paths to multiple Cargo workspaces and their target directories, separated by newlines."
+    required: false
+  cache-directories:
+    description: "Additional non workspace directories to be cached, separated by newlines."
+    required: false
+  cache-on-failure:
+    description: "Cache even if the build fails."
+    default: "true"
+    required: false
+  cache-key:
+    description: "An additional cache key that is added alongside the automatic `job`-based cache key and can be used to further differentiate jobs."
+    required: false
+  cache-shared-key:
+    description: "A cache key that is used instead of the automatic `job`-based key, and is stable over multiple jobs."
+    required: false
+  cache-bin:
+    description: "Determines whether to cache ${CARGO_HOME}/bin."
+    required: false
+    default: "true"
+  cache-provider:
+    description: "Determines which provider to use for caching. Options are github, buildjet, or warpbuild. Defaults to github."
+    required: false
+    default: "github"
+  cache-all-crates:
+    description: "Determines which crates are cached. If `true` all crates will be cached, otherwise only dependent crates will be cached."
+    required: false
+    default: "false"
+  cache-workspace-crates:
+    description: "Determines which crates are cached. If `true` all crates will be cached, otherwise only dependent crates will be cached."
+    required: false
+    default: "false"
+  matcher:
+    description: "Enable the Rust problem matcher"
+    required: false
+    default: "true"
+  rustflags:
+    description: "set RUSTFLAGS environment variable, set to empty string to avoid overwriting build.rustflags"
+    required: false
+    default: "-D warnings"
+  override:
+    description: "Setup the last installed toolchain as the default via `rustup override`"
+    required: false
+    default: "true"
+  rust-src-dir:
+    description: "Specify path from root directory to the Rust source directory. By default root directory will be used."
+    required: false
 
 outputs:
   rustc-version:
@@ -52,17 +98,21 @@ runs:
       shell: bash
 
     - id: flags
-      run: |
-        : construct rustup command line
-        echo "targets=$(for t in ${targets//,/ }; do echo -n ' --target' $t; done)" >> $GITHUB_OUTPUT
-        echo "components=$(for c in ${components//,/ }; do echo -n ' --component' $c; done)" >> $GITHUB_OUTPUT
-        echo "downgrade=${{inputs.toolchain == 'nightly' && inputs.components && ' --allow-downgrade' || ''}}" >> $GITHUB_OUTPUT
       env:
         targets: ${{inputs.target}}
         components: ${{inputs.components}}
       shell: bash
+      run: |
+        : construct rustup command line
+        echo "targets=$(for t in ${targets//,/ }; do echo -n ' --target' $t; done)" >> $GITHUB_OUTPUT
+        echo "components=$(for c in ${components//,/ }; do echo -n ' --component' $c; done)" >> $GITHUB_OUTPUT
+        echo "downgrade=${{contains(inputs.toolchain, 'nightly') && inputs.components && ' --allow-downgrade' || ''}}" >> $GITHUB_OUTPUT
+
     # The environment variables always need to be set before the caching action
-    - name: "Setting Environment Variables"
+    - name: Setting Environment Variables
+      env:
+        NEW_RUSTFLAGS: ${{inputs.rustflags}}
+      shell: bash
       run: |
         if [[ ! -v CARGO_INCREMENTAL ]]; then
           echo "CARGO_INCREMENTAL=0" >> $GITHUB_ENV
@@ -76,8 +126,8 @@ runs:
         if [[ ! -v RUST_BACKTRACE ]]; then
           echo "RUST_BACKTRACE=short" >> $GITHUB_ENV
         fi
-        if [[ ! -v RUSTFLAGS ]]; then
-          echo "RUSTFLAGS=-D warnings" >> $GITHUB_ENV
+        if [[ ( ! -v RUSTFLAGS ) && $NEW_RUSTFLAGS != "" ]]; then
+          echo "RUSTFLAGS=$NEW_RUSTFLAGS" >> $GITHUB_ENV
         fi
         # Enable faster sparse index on nightly
         # The value is ignored on stable and causes no problems
@@ -85,34 +135,84 @@ runs:
         if [[ ! -v CARGO_UNSTABLE_SPARSE_REGISTRY ]]; then
           echo "CARGO_UNSTABLE_SPARSE_REGISTRY=true" >> $GITHUB_ENV
         fi
+        if [[ ! -v CARGO_REGISTRIES_CRATES_IO_PROTOCOL ]]; then
+          echo "CARGO_REGISTRIES_CRATES_IO_PROTOCOL=sparse" >> $GITHUB_ENV
+        fi
+
+    - name: Install Rust Problem Matcher
+      if: inputs.matcher == 'true'
       shell: bash
-    - name: "Install Rust Problem Matcher"
       run: echo "::add-matcher::${{ github.action_path }}/rust.json"
-      shell: bash
 
     - name: Install rustup, if needed
+      shell: bash
       run: |
         if ! command -v rustup &> /dev/null ; then
           curl --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused -fsSL "https://sh.rustup.rs" | sh -s -- --default-toolchain none -y
-          echo "${CARGO_HOME:-$HOME/.cargo}/bin" >> $GITHUB_PATH
+
+          # Resolve the correct CARGO_HOME path depending on OS
+          if [[ "$RUNNER_OS" == "Windows" ]]; then
+            echo "${CARGO_HOME:-$USERPROFILE/.cargo}/bin" | sed 's|/|\\|g' >> $GITHUB_PATH
+          else
+            echo "${CARGO_HOME:-$HOME/.cargo}/bin" >> $GITHUB_PATH
+          fi
         fi
-      if: runner.os != 'Windows'
+      env:
+        RUNNER_OS: "${{ runner.os }}"
+
+    - name: rustup toolchain install ${{inputs.toolchain || 'stable'}}
+      env:
+        toolchain: ${{inputs.toolchain}}
+        targets: ${{inputs.target}}
+        components: ${{inputs.components}}
+        override: ${{inputs.override}}
+        rust_src_dir: ${{inputs.rust-src-dir}}
       shell: bash
-    - name: rustup toolchain install ${{inputs.toolchain}}
       run: |
-        if [[ -f "rust-toolchain" || -f "rust-toolchain.toml" ]]
+        # Check if value is set
+        if [[ -n "$rust_src_dir" ]]
+        then
+          # If value is set the directory must exist
+          if [[ -d "$rust_src_dir" ]]
+          then
+            cd "$rust_src_dir"
+          else
+            echo "'rust-src-dir' does not point to an existing directory" >&2
+            echo "The value of 'rust-src-dir' is: ${rust_src_dir}" >&2
+            exit 1
+          fi
+        fi
+        if [[ -z "$toolchain" && ( -f "rust-toolchain" || -f "rust-toolchain.toml") ]]
         then
           # Install the toolchain as specified in the file
-          # Might break at some point: https://github.com/rust-lang/rustup/issues/1397
-          rustup show
+          # rustup show is the old way that implicitly installed a toolchain
+          # rustup toolchain install is the new explicit way
+          # https://github.com/rust-lang/rustup/issues/3635#issuecomment-2343511297
+          rustup show active-toolchain || rustup toolchain install
+          if [[ -n $components ]]; then
+            rustup component add ${components//,/ }
+          fi
+          if [[ -n $targets ]]; then
+            rustup target add ${targets//,/ }
+          fi
         else
-          rustup toolchain install ${{inputs.toolchain}}${{steps.flags.outputs.targets}}${{steps.flags.outputs.components}} --profile minimal${{steps.flags.outputs.downgrade}} --no-self-update
-          rustup default ${{inputs.toolchain}}
+          if [[ -z "$toolchain" ]]
+          then
+            toolchain=stable
+          fi
+          rustup toolchain install ${toolchain//,/ } ${{steps.flags.outputs.targets}}${{steps.flags.outputs.components}} --profile minimal${{steps.flags.outputs.downgrade}} --no-self-update
+          # Take the last element from the list
+          if [[ "$override" == "true" ]]
+          then
+            rustup override set ${toolchain//*,/ }
+          fi
         fi
-      shell: bash
 
-    - name: Print installed versions
-      id: versions
+    - id: versions
+      name: Print installed versions
+      shell: bash
+      # Switch to the Rust sub-directory
+      working-directory: ${{inputs.rust-src-dir || '.'}}
       run: |
         echo "rustc-version=$(rustc --version)" >> $GITHUB_OUTPUT
         rustc --version --verbose
@@ -124,22 +224,29 @@ runs:
         DATE=$(rustc --version --verbose | sed -ne 's/^commit-date: \(20[0-9][0-9]\)-\([01][0-9]\)-\([0-3][0-9]\)$/\1\2\3/p')
         HASH=$(rustc --version --verbose | sed -ne 's/^commit-hash: //p')
         echo "cachekey=$(echo $DATE$HASH | head -c12)" >> $GITHUB_OUTPUT
-      shell: bash
 
-    # Copied from dtolnay/rust-toolchain and adapted
-    # https://github.com/dtolnay/rust-toolchain/blob/25dc93b901a87e864900a8aec6c12e9aa794c0c3/action.yml#L100-L108
-    - name: "Enable cargo sparse registry on stable"
+    - name: Downgrade registry access protocol when needed
+      shell: bash
       run: |
-        # except on 1.66 and 1.67, on which it is unstable
-        # Not all 1.68.0-nightly versions support it either
+        # Not all versions support setting CARGO_REGISTRIES_CRATES_IO_PROTOCOL
+        # On versions 1.66, 1.67, and 1.68.0-nightly the value "sparse" is still unstable.
         # https://github.com/dtolnay/rust-toolchain/pull/69#discussion_r1107268108
-        if [[ ! -v CARGO_REGISTRIES_CRATES_IO_PROTOCOL ]]; then
-          if echo "${{steps.versions.outputs.rustc-version}}" | grep --invert --quiet '^rustc \(1\.6[67]\.\|1\.68\.0-nightly\)'; then
-            echo "CARGO_REGISTRIES_CRATES_IO_PROTOCOL=sparse" >> $GITHUB_ENV
-          fi
+        # If we detect an incompatible value, set it to "git" which is always supported.
+        if [[ "${{steps.versions.outputs.rustc-version}}" =~ ^rustc\ (1\.6[67]\.|1\.68\.0-nightly) && "${CARGO_REGISTRIES_CRATES_IO_PROTOCOL}" == "sparse" ]]; then
+          echo "Downgrade cargo registry protocol to git"
+          echo "CARGO_REGISTRIES_CRATES_IO_PROTOCOL=git" >> $GITHUB_ENV
         fi
-      shell: bash
 
-    - name: "Setup Rust Caching"
+    - name: Setup Rust Caching
       if: inputs.cache == 'true'
-      uses: Swatinem/rust-cache@v2
+      uses: Swatinem/rust-cache@f13886b937689c021905a6b90929199931d60db1 # v2.8.1
+      with:
+        workspaces: ${{ inputs.cache-workspaces || inputs.rust-src-dir }}
+        cache-directories: ${{inputs.cache-directories}}
+        cache-on-failure: ${{inputs.cache-on-failure}}
+        cache-bin: ${{inputs.cache-bin}}
+        cache-provider: ${{inputs.cache-provider}}
+        cache-all-crates: ${{inputs.cache-all-crates}}
+        cache-workspace-crates: ${{inputs.cache-workspace-crates}}
+        key: ${{inputs.cache-key}}
+        shared-key: ${{inputs.cache-shared-key}}

rust.json

@@ -5,7 +5,7 @@
             "severity": "warning",
             "pattern": [
                 {
-                    "regexp": "^(Diff in (.+)) at line (\\d+):$",
+                    "regexp": "^(Diff in (.+))(?: at line |:)(\\d+):$",
                     "message": 1,
                     "file": 2,
                     "line": 3
@@ -16,16 +16,16 @@
             "owner": "clippy",
             "pattern": [
                 {
-                    "regexp": "^(warning|warn|error)(\\[(.*)\\])?: (.*)$",
+                    "regexp": "^(?:\\x1b\\[[\\d;]+m)*(warning|warn|error)(?:\\x1b\\[[\\d;]+m)*(\\[(.*)\\])?(?:\\x1b\\[[\\d;]+m)*:(?:\\x1b\\[[\\d;]+m)* ([^\\x1b]*)(?:\\x1b\\[[\\d;]+m)*$",
                     "severity": 1,
                     "message": 4,
                     "code": 3
                 },
                 {
-                    "regexp": "^([\\s->=]*(.*):(\\d*):(\\d*)|.*)$",
-                    "file": 2,
-                    "line": 3,
-                    "column": 4
+                    "regexp": "^(?:\\x1b\\[[\\d;]+m)*\\s*(?:\\x1b\\[[\\d;]+m)*\\s*--> (?:\\x1b\\[[\\d;]+m)*(.*):(\\d*):(\\d*)(?:\\x1b\\[[\\d;]+m)*$",
+                    "file": 1,
+                    "line": 2,
+                    "column": 3
                 }
             ]
         }

test-workspace/Cargo.lock

@@ -0,0 +1,16 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "ci"
+version = "0.1.0"
+dependencies = [
+ "serde_as",
+]
+
+[[package]]
+name = "serde_as"
+version = "0.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ee4afe4c5c3b69699c4267ae42b838e911466d7ca0005046adc93ac95bb16dd"

test-workspace/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "ci"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+serde_as = "0.0.1"

test-workspace/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}