Require opt-in via force-arch to run x86 on macOS arm (#352)

IanButterworth · DilumAluthge · web-flow · commit 44a615affb11 · 2026-03-04T15:18:16.000-05:00
* require opt-in via `force-arch` to run x86 on macOS arm * Update src/setup-julia.ts * Run `make everything-from-scratch`, and check-in * Fix CI in #352 (#373) * Fix CI in #352 * Clarify a statement about the support for 32-bit builds --------- Co-authored-by: Dilum Aluthge <dilum@aluthge.com>
diff --git a/.github/workflows/example-builds-nightly.yml b/.github/workflows/example-builds-nightly.yml
@@ -20,13 +20,23 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        julia-version: [nightly, 1.13-nightly]
-        julia-arch: [x64, x86]
-        os: [ubuntu-latest, macOS-latest, windows-latest]
+        julia-version:
+          - nightly
+          - 1.13-nightly
+        julia-wordsize:
+          - 64
+          - 32
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-15-intel # Intel
+          - macos-latest # Apple Silicon
         # 32-bit Julia binaries are not available on macOS
         exclude:
-          - os: macOS-latest
-            julia-arch: x86
+          - os: macos-15-intel # Intel
+            julia-wordsize: 32
+          - os: macos-latest # Apple Silicon
+            julia-wordsize: 32
 
     steps:
       - uses: actions/checkout@v6.0.2
@@ -47,7 +57,14 @@ jobs:
         uses: ./
         with:
           version: ${{ matrix.julia-version }}
-          arch: ${{ matrix.julia-arch }}
+          # If `julia-wordsize` is 32, then we set `arch` to `x86`, because we know that
+          # 32-bit builds of Julia are only available for x86.
+          #
+          # If `julia-wordsize` is 64, then we set `arch` to `${{ runner.arch }}`, which
+          # GitHub will automatically expand to the correct value (`x86_64` or `aarch64`)
+          # based on the architecture of the underlying GitHub Runner (virtual machine).
+          arch: ${{ matrix.julia-wordsize == '32' && 'x86' || runner.arch }}
+
       - run: julia --version
       - run: julia --compile=min -O0 -e 'import InteractiveUtils; InteractiveUtils.versioninfo()'
       - name: "Check that the correct julia is used and that archive mtimes are maintained"
diff --git a/.github/workflows/example-builds.yml b/.github/workflows/example-builds.yml
@@ -12,31 +12,50 @@ on:
   pull_request:
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 jobs:
   test:
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
     strategy:
       fail-fast: false
       matrix:
-       # include '1.6' here to test info message about lts tag existing
-        julia-version: ['1.0.5', '1.2', '^1.5.0-beta1', '1', '1.6', 'lts', 'pre']
-        julia-arch: [x64, x86]
-        os: [ubuntu-latest, macOS-latest, windows-latest]
+        julia-version:
+          - '1.0.5'
+          - '1.2'
+          - '^1.5.0-beta1'
+          - '1'
+          - '1.6'
+          - '1.10' # include '1.10' here to test info message about lts tag existing
+          - 'lts'
+          - 'pre'
+        julia-wordsize:
+          - 64
+          - 32
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-15-intel # Intel
+          - macos-latest # Apple Silicon
         # 32-bit Julia binaries are not available on macOS
         exclude:
-          - os: macOS-latest
-            julia-arch: x86
-        include:
-          - os: macOS-latest
-            julia-arch: aarch64
-            julia-version: 'lts'
-          - os: macOS-latest
-            julia-arch: aarch64
-            julia-version: '1'
-
+          - os: macos-15-intel # Intel
+            julia-wordsize: 32
+          - os: macos-latest # Apple Silicon
+            julia-wordsize: 32
+        # Julia versions prior to 1.8 do not have native builds for Apple Silicon
+          - os: macos-latest # Apple Silicon
+            julia-version: '1.0.5'
+          - os: macos-latest # Apple Silicon
+            julia-version: '1.2'
+          - os: macos-latest # Apple Silicon
+            julia-version: '1.6'
     steps:
       - uses: actions/checkout@v6.0.2
+        with:
+          persist-credentials: false
 
       - uses: actions/setup-node@v6
         if: ${{ ! startsWith(github.ref, 'refs/heads/releases') }}
@@ -55,7 +74,14 @@ jobs:
         uses: ./
         with:
           version: ${{ matrix.julia-version }}
-          arch: ${{ matrix.julia-arch }}
+          # If `julia-wordsize` is 32, then we set `arch` to `x86`, because we know that
+          # Tier 1 32-bit builds of Julia are only available for x86.
+          #
+          # If `julia-wordsize` is 64, then we set `arch` to `${{ runner.arch }}`, which
+          # GitHub will automatically expand to the correct value (`x86_64` or `aarch64`)
+          # based on the architecture of the underlying GitHub Runner (virtual machine).
+          arch: ${{ matrix.julia-wordsize == '32' && 'x86' || runner.arch }}
+
       - run: julia --version
       - run: julia --compile=min -O0 -e 'import InteractiveUtils; InteractiveUtils.versioninfo()'
       - name: "Check that the correct julia is used and that archive mtimes are maintained"
diff --git a/README.md b/README.md
@@ -56,6 +56,18 @@ This action sets up a Julia environment for use in actions by downloading a spec
     # Specifying 'default' uses the architecture of the runner executing the job.
     arch: 'default'
 
+    # Force the use of the specified architecture even when it may be suboptimal on the runner.
+    #
+    # By default, requesting x86 or x64 on an aarch64 macOS runner (Apple Silicon) will fail with an error,
+    # as this is usually a misconfiguration. Set this to 'true' to override the error and allow the installation.
+    #
+    # Note: x64 Julia can run on Apple Silicon via Rosetta 2, but native aarch64 is typically preferred.
+    #
+    # Supported values: true | false
+    #
+    # Default: false
+    force-arch: 'false'
+
     # Set the display setting for printing InteractiveUtils.versioninfo() after installing.
     #
     # Starting Julia and running InteractiveUtils.versioninfo() takes a significant amount of time (1s or ~10% of the total build time in testing),
diff --git a/action.yml b/action.yml
@@ -13,6 +13,10 @@ inputs:
     description: 'Architecture of the Julia binaries. Defaults to the architecture of the runner executing the job.'
     required: false
     default: 'default'
+  force-arch:
+    description: 'Force the use of the specified architecture even when it may be suboptimal on the runner (e.g., x86 on Apple Silicon macOS runners). By default, requesting x86/x64 on aarch64 macOS runners will fail with an error.'
+    required: false
+    default: 'false'
   show-versioninfo:
     description: 'Display InteractiveUtils.versioninfo() after installing'
     required: false
diff --git a/dist/index.js b/dist/index.js
@@ -585,6 +585,7 @@ function run() {
             const versionInput = core.getInput('version').trim();
             const includePrereleases = core.getInput('include-all-prereleases').trim() == 'true';
             const originalArchInput = core.getInput('arch').trim();
+            const forceArch = core.getInput('force-arch').trim() == 'true';
             const projectInput = core.getInput('project').trim(); // Julia project file
             // It can easily happen that, for example, a workflow file contains an input `version: ${{ matrix.julia-version }}`
             // while the strategy matrix only contains a key `${{ matrix.version }}`.
@@ -601,7 +602,12 @@ function run() {
                 throw new Error(`Arch input must not be null`);
             }
             if (originalArchInput == 'x64' && os.platform() == 'darwin' && os.arch() == 'arm64') {
-                core.warning('[setup-julia] x64 arch has been requested on a macOS runner that has an arm64 (Apple Silicon) architecture. You may have meant to use the "aarch64" arch instead (or left it unspecified for the correct default).');
+                if (forceArch) {
+                    core.warning('[setup-julia] x64 arch has been requested on a macOS runner that has an arm64 (Apple Silicon) architecture. The "force-arch" input is set to "true", so proceeding with x64 installation. Note that this will mean Julia will be run under Rosetta emulation.');
+                }
+                else {
+                    throw new Error('[setup-julia] x64 arch has been requested on a macOS runner that has an arm64 (Apple Silicon) architecture. You may have meant to use the "aarch64" arch instead (or "default" or left it unspecified for the correct default). To force the use of x64 on this runner, set the "force-arch" input to "true".');
+                }
             }
             let processedArchInput;
             if (originalArchInput == "default") {
diff --git a/lib/setup-julia.js b/lib/setup-julia.js
diff --git a/src/setup-julia.ts b/src/setup-julia.ts
@@ -45,6 +45,7 @@ async function run() {
         const versionInput = core.getInput('version').trim()
         const includePrereleases = core.getInput('include-all-prereleases').trim() == 'true'
         const originalArchInput = core.getInput('arch').trim()
+        const forceArch = core.getInput('force-arch').trim() == 'true'
         const projectInput = core.getInput('project').trim()  // Julia project file
 
         // It can easily happen that, for example, a workflow file contains an input `version: ${{ matrix.julia-version }}`
@@ -63,7 +64,11 @@ async function run() {
         }
 
         if (originalArchInput == 'x64' && os.platform() == 'darwin' && os.arch() == 'arm64') {
-            core.warning('[setup-julia] x64 arch has been requested on a macOS runner that has an arm64 (Apple Silicon) architecture. You may have meant to use the "aarch64" arch instead (or left it unspecified for the correct default).')
+            if (forceArch) {
+                core.warning('[setup-julia] x64 arch has been requested on a macOS runner that has an arm64 (Apple Silicon) architecture. The "force-arch" input is set to "true", so proceeding with x64 installation. Note that this will mean Julia will be run under Rosetta emulation.')
+            } else {
+                throw new Error('[setup-julia] x64 arch has been requested on a macOS runner that has an arm64 (Apple Silicon) architecture. You may have meant to use the "aarch64" arch instead (or "default" or left it unspecified for the correct default). To force the use of x64 on this runner, set the "force-arch" input to "true".')
+            }
         }
 
         let processedArchInput: string;
