Support force-non-host toolchains

.github/workflows/ci.yml

@@ -43,3 +43,19 @@ jobs:
         if: matrix.rust == 'nightly' || matrix.rust == 'beta' || matrix.rust == 'stable'
       - run: cargo check
         if: matrix.rust == 'nightly' || matrix.rust == 'beta' || matrix.rust == 'stable'
+
+  non-host:
+    name: Non-host toolchain on Windows
+    runs-on: windows-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v7
+      - uses: ./
+        with:
+          toolchain: stable-i686-pc-windows-msvc
+          force-non-host: true
+      - name: Check the active toolchain and compiler host
+        run: |
+          test "$(rustup show active-toolchain)" = "stable-i686-pc-windows-msvc (default)"
+          rustc --version --verbose | grep -Fx 'host: i686-pc-windows-msvc'
+        shell: bash

README.md

@@ -53,6 +53,10 @@ All inputs are optional.
   <td><code>components</code></td>
   <td>Comma-separated string of additional components to install e.g. <code>clippy, rustfmt</code></td>
 </tr>
+<tr>
+  <td><code>force-non-host</code></td>
+  <td>Pass <code>--force-non-host</code> to rustup when installing and selecting the default toolchain. Defaults to <code>false</code>. Set to <code>true</code> when intentionally using a non-host toolchain that the host can run.</td>
+</tr>
 </table>
 
 <br>

action.yml

@@ -18,6 +18,10 @@ inputs:
   components:
     description: Comma-separated list of components to be additionally installed
     required: false
+  force-non-host:
+    description: Allow installing and selecting a toolchain that does not match the host platform
+    required: false
+    default: "false"
 
 outputs:
   cachekey:
@@ -60,6 +64,7 @@ runs:
         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)" >> $GITHUB_OUTPUT
         echo "downgrade=${{steps.parse.outputs.toolchain == 'nightly' && inputs.components && ' --allow-downgrade' || ''}}" >> $GITHUB_OUTPUT
+        echo "force-non-host=${{inputs.force-non-host == 'true' && ' --force-non-host' || ''}}" >> $GITHUB_OUTPUT
       env:
         targets: ${{inputs.targets || inputs.target || ''}}
         components: ${{inputs.components}}
@@ -89,13 +94,13 @@ runs:
       shell: bash
 
     - name: rustup toolchain install ${{steps.parse.outputs.toolchain}}
-      run: rustup toolchain install ${{steps.parse.outputs.toolchain}}${{steps.flags.outputs.targets}}${{steps.flags.outputs.components}} --profile minimal${{steps.flags.outputs.downgrade}} --no-self-update
+      run: rustup toolchain install ${{steps.parse.outputs.toolchain}}${{steps.flags.outputs.targets}}${{steps.flags.outputs.components}} --profile minimal${{steps.flags.outputs.downgrade}} --no-self-update${{steps.flags.outputs.force-non-host}}
       env:
         RUSTUP_PERMIT_COPY_RENAME: 1
       shell: bash
 
     - name: rustup default ${{steps.parse.outputs.toolchain}}
-      run: rustup default ${{steps.parse.outputs.toolchain}}
+      run: rustup default ${{steps.parse.outputs.toolchain}}${{steps.flags.outputs.force-non-host}}
       shell: bash
       continue-on-error: true  # https://github.com/dtolnay/rust-toolchain/issues/127