feat: support Julia versions from .tool-versions

Author: DilumAluthge-LLM

README.md

@@ -45,6 +45,17 @@ This action sets up a Julia environment for use in actions by downloading a spec
     # Default: '1'
     version: '1'
 
+    # Read the Julia version from a .tool-versions file.
+    #
+    # This is useful for repositories that already pin Julia with asdf or mise-en-place.
+    # The file must contain a Julia entry with major, minor, and patch versions, for example:
+    #     julia 1.10.11
+    #
+    # The `version-file` input cannot be used together with the `version` input.
+    #
+    # Default: ''
+    version-file: '.tool-versions'
+
     # The architecture of the Julia binaries.
     #
     # Please note that installing aarch64 binaries only makes sense on self-hosted aarch64 runners.
@@ -128,6 +139,24 @@ You can either specify specific Julia versions or version ranges. If you specify
 >
 > It is strongly recommended to wrap versions in quotes. Otherwise, the YAML parser used by GitHub Actions parses certain versions as numbers which causes the wrong version to be selected. For example, `1.0` may be parsed as `1`.
 
+Alternatively, set `version-file` to a `.tool-versions` file containing a Julia entry:
+
+```yaml
+steps:
+- uses: actions/checkout@v6
+- uses: julia-actions/setup-julia@v3
+  with:
+    version-file: '.tool-versions'
+```
+
+For example, the `.tool-versions` file might contain:
+
+```text
+julia 1.10.11
+```
+
+The Julia entry must specify major, minor, and patch versions. The `version` and `version-file` inputs cannot be used together.
+
 #### Examples
 
 - `'1.2.0'` is a valid semver version. The action will try to download exactly this version. If it's not available, the build step will fail.

__tests__/installer.test.ts

@@ -1,6 +1,8 @@
 // The testing setup has been derived from the actions/setup-go@bc6edb5 action.
 // Check README.md for licence information.
 
+import * as fs from 'fs'
+import * as os from 'os'
 import * as path from 'path'
 
 import * as io from '@actions/io'
@@ -40,6 +42,85 @@ process.env['RUNNER_TEMP'] = tempDir
 import * as installer from '../src/installer'
 import exp from 'constants'
 
+describe("readJuliaVersionFromToolVersionsFile tests", () => {
+    let tempDirForToolVersions: string
+
+    beforeEach(() => {
+        tempDirForToolVersions = fs.mkdtempSync(path.join(os.tmpdir(), "setup-julia-tool-versions-"))
+    })
+
+    afterEach(() => {
+        fs.rmSync(tempDirForToolVersions, { force: true, recursive: true })
+    })
+
+    function writeToolVersions(content: string): string {
+        const versionFilePath = path.join(tempDirForToolVersions, ".tool-versions")
+        fs.writeFileSync(versionFilePath, content)
+        return versionFilePath
+    }
+
+    it("Reads a Julia version", () => {
+        const versionFilePath = writeToolVersions("julia 1.10.4\n")
+        expect(installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toEqual("1.10.4")
+    })
+
+    it("Handles comments and blank lines", () => {
+        const versionFilePath = writeToolVersions("\n# tools\n\njulia 1.11.0\n")
+        expect(installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toEqual("1.11.0")
+    })
+
+    it("Finds Julia among multiple tools", () => {
+        const versionFilePath = writeToolVersions("nodejs 24.11.1\njulia 1.10.7\npython 3.14.0\n")
+        expect(installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toEqual("1.10.7")
+    })
+
+    it("Uses the first Julia version token", () => {
+        const versionFilePath = writeToolVersions("julia 1.10.4 1.11.1 # fallback\n")
+        expect(installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toEqual("1.10.4")
+    })
+
+    it("Reads a prerelease Julia version", () => {
+        const versionFilePath = writeToolVersions("julia 1.11.0-rc1\n")
+        expect(installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toEqual("1.11.0-rc1")
+    })
+
+    it("Throws when the Julia entry only specifies major and minor", () => {
+        const versionFilePath = writeToolVersions("julia 1.10\n")
+        expect(() => installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toThrow("must specify major, minor, and patch")
+    })
+
+    it("Throws when the Julia entry only specifies major", () => {
+        const versionFilePath = writeToolVersions("julia 1\n")
+        expect(() => installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toThrow("must specify major, minor, and patch")
+    })
+
+    it("Throws when the Julia entry uses a version keyword", () => {
+        const versionFilePath = writeToolVersions("julia lts\n")
+        expect(() => installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toThrow("must specify major, minor, and patch")
+    })
+
+    it("Throws when no Julia entry exists", () => {
+        const versionFilePath = writeToolVersions("nodejs 24.11.1\npython 3.14.0\n")
+        expect(() => installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toThrow("No Julia version found")
+    })
+
+    it("Throws when the Julia entry has no version", () => {
+        const versionFilePath = writeToolVersions("julia\n")
+        expect(() => installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toThrow("No Julia version found")
+    })
+
+    it("Throws when the version file is not named .tool-versions", () => {
+        const versionFilePath = path.join(tempDirForToolVersions, "julia-version")
+        fs.writeFileSync(versionFilePath, "julia 1.10.4\n")
+        expect(() => installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toThrow("only supports .tool-versions")
+    })
+
+    it("Throws when the version file does not exist", () => {
+        const versionFilePath = path.join(tempDirForToolVersions, ".tool-versions")
+        expect(() => installer.readJuliaVersionFromToolVersionsFile(versionFilePath)).toThrow("does not exist")
+    })
+})
+
 describe("getProjectFilePath tests", () => {
     let orgJuliaProject
     let orgWorkingDir

action.yml

@@ -3,8 +3,11 @@ description: 'Setup a Julia environment and add it to the PATH'
 author: 'Sascha Mann'
 inputs:
   version:
-    description: 'The Julia version to download (if necessary) and use. Use a string input to avoid unwanted decimal conversion e.g. 1.10 without quotes will be interpreted as 1.1. Examples: "1", "1.10", "lts", "pre"'
-    default: '1'
+    description: 'The Julia version to download (if necessary) and use. Use a string input to avoid unwanted decimal conversion e.g. 1.10 without quotes will be interpreted as 1.1. Examples: "1", "1.10", "lts", "pre". Defaults to "1" when neither version nor version-file is set.'
+    required: false
+  version-file:
+    description: 'Path to a .tool-versions file containing the Julia version to download (if necessary) and use. Cannot be used simultaneously with the `version` input.'
+    required: false
   include-all-prereleases:
     description: 'Include prereleases when matching the Julia version to available versions.'
     required: false

src/installer.ts

@@ -80,6 +80,45 @@ export async function getJuliaVersions(versionInfo): Promise<string[]> {
     return versions
 }
 
+/**
+ * @returns The Julia version specified in an asdf/mise-en-place .tool-versions file.
+ */
+export function readJuliaVersionFromToolVersionsFile(versionFilePath: string): string {
+    if (path.basename(versionFilePath) !== ".tool-versions") {
+        throw new Error(`The version-file input only supports .tool-versions files: ${versionFilePath}`)
+    }
+
+    if (!fs.existsSync(versionFilePath)) {
+        throw new Error(`The specified version-file does not exist: ${versionFilePath}`)
+    }
+
+    const lines = fs.readFileSync(versionFilePath, 'utf8').split(/\r\n|\r|\n/)
+    for (let line of lines) {
+        line = line.trim()
+
+        if (!line || line.startsWith("#")) {
+            continue
+        }
+
+        const match = line.match(/^julia(?:\s+(.+))?$/)
+        if (!match) {
+            continue
+        }
+
+        const version = match[1]?.trim().split(/\s+/)[0] || ""
+        if (!version || version.startsWith("#")) {
+            throw new Error(`No Julia version found in ${versionFilePath}`)
+        }
+        if (!semver.valid(version)) {
+            throw new Error(`The Julia version in ${versionFilePath} must specify major, minor, and patch versions: ${version}`)
+        }
+
+        return version
+    }
+
+    throw new Error(`No Julia version found in ${versionFilePath}`)
+}
+
 /**
  * @returns The path to the Julia project file
  */

src/setup-julia.ts

@@ -43,20 +43,41 @@ async function run() {
 
         // Inputs.
         // Note that we intentionally strip leading and lagging whitespace by using `.trim()`
-        const versionInput = core.getInput('version').trim()
+        const rawVersionInput = core.getInput('version').trim()
+        const versionFileInput = core.getInput('version-file').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 }}`.
-        // In that case, we want the action to fail, rather than trying to download julia from an URL that's missing parts and 404ing.
-        // We _could_ fall back to the default but that means that builds silently do things differently than they're meant to, which
-        // is worse than failing the build.
-        if (!versionInput) { // if `versionInput` is an empty string
+        // `core.getInput('version')` returns an empty string both when the input is
+        // omitted and when it is explicitly set to an empty value. Those cases now
+        // differ: omitted means use `version-file` or the default `1`, while an
+        // explicitly empty value usually indicates a typo like
+        // `version: ${{ matrix.julia-version }}` with no matching matrix key.
+        // GitHub exposes provided inputs as `INPUT_*` environment variables, so
+        // `INPUT_VERSION` lets us preserve the old explicit-empty error.
+        const versionInputWasProvided = process.env.INPUT_VERSION !== undefined
+        if (versionInputWasProvided && !rawVersionInput) { // if `rawVersionInput` is an empty string
             throw new Error('Version input must not be null')
         }
+        if (rawVersionInput && versionFileInput) {
+            throw new Error('The "version" and "version-file" inputs cannot both be set')
+        }
+
+        let versionInput = rawVersionInput
+        if (!versionInput && versionFileInput) {
+            // GitHub Actions does not apply a step-specific working directory to `uses:` steps,
+            // so relative `version-file` paths are resolved from the checked-out workspace.
+            const workspace = process.env.GITHUB_WORKSPACE || process.cwd()
+            const versionFilePath = path.isAbsolute(versionFileInput) ? versionFileInput : path.join(workspace, versionFileInput)
+            versionInput = installer.readJuliaVersionFromToolVersionsFile(versionFilePath)
+            core.info(`Resolved ${versionFileInput} as ${versionInput}`)
+        }
+        if (!versionInput) {
+            versionInput = '1'
+        }
+
         if (versionInput == '1.6') {
             core.notice('[setup-julia] If you are testing 1.6 as a Long Term Support (lts) version, consider using the new "lts" version specifier instead of "1.6" explicitly, which will automatically resolve the current lts.')
         }