Resolve min as the earliest compatible Julia version (compatible with the user's project) (#202)

* Support the special version "MIN"

* Support JULIA_PROJECT

* Add tests

* Add forgotten test fixtures

* Get latest prerelease/release

* No special pre-release behaviour

* Add test for NPM semver difference

* Robust test suite

* Disallow less-than-equal

* Refactor validJuliaCompatRange to return a validRange

* Rename MIN to min

* Rename getProjectFile to getProjectFilePath

* Comment on "project" input

* Additional tests for getProjectFilePath

* Add comment on `juliaCompatRange`

Co-authored-by: Dilum Aluthge <dilum@aluthge.com>

* Update dependencies

---------

Co-authored-by: Dilum Aluthge <dilum@aluthge.com>

README.md

@@ -71,6 +71,11 @@ This action sets up a Julia environment for use in actions by downloading a spec
     #
     # Default: false
     show-versioninfo: ''
+
+    # Set the path to the project directory or file to use when resolving some versions (e.g. `min`).
+    #
+    # Defaults to using JULIA_PROJECT if defined, otherwise '.'
+    project: ''
 ```
 
 ### Outputs
@@ -121,6 +126,7 @@ You can either specify specific Julia versions or version ranges. If you specify
 - `'pre'` will install the latest prerelease build (RCs, betas, and alphas).
 - `'nightly'` will install the latest nightly build.
 - `'1.7-nightly'` will install the latest nightly build for the upcoming 1.7 release. This version will only be available during certain phases of the Julia release cycle.
+- `'min'` will install the earliest supported version of Julia compatible with the project. Especially useful in monorepos.
 
 Internally the action uses node's semver package to resolve version ranges. Its [documentation](https://github.com/npm/node-semver#advanced-range-syntax) contains more details on the version range syntax. You can test what version will be selected for a given input in this JavaScript [REPL](https://repl.it/@SaschaMann/setup-julia-version-logic).
 

__tests__/installer.test.ts

@@ -38,6 +38,135 @@ process.env['RUNNER_TOOL_CACHE'] = toolDir
 process.env['RUNNER_TEMP'] = tempDir
 
 import * as installer from '../src/installer'
+import exp from 'constants'
+
+describe("getProjectFilePath tests", () => {
+    let orgJuliaProject
+    let orgWorkingDir
+
+    beforeEach(() => {
+        orgJuliaProject = process.env["JULIA_PROJECT"]
+        orgWorkingDir = process.cwd()
+        delete process.env["JULIA_PROJECT"]
+    })
+
+    afterEach(() => {
+        process.env["JULIA_PROJECT"] = orgJuliaProject
+        process.chdir(orgWorkingDir)
+    })
+
+    it("Can determine project file is missing", () => {
+        expect(() => installer.getProjectFilePath("DNE.toml")).toThrow("Unable to locate project file")
+        expect(() => installer.getProjectFilePath(fixtureDir)).toThrow("Unable to locate project file")
+        expect(() => installer.getProjectFilePath()).toThrow("Unable to locate project file")
+    })
+
+    it('Can determine project file from a directory', () => {
+        expect(installer.getProjectFilePath(path.join(fixtureDir, "PkgA"))).toEqual(path.join(fixtureDir, "PkgA", "Project.toml"))
+        expect(installer.getProjectFilePath(path.join(fixtureDir, "PkgB"))).toEqual(path.join(fixtureDir, "PkgB", "JuliaProject.toml"))
+    })
+
+    it("Prefers using JuliaProject.toml over Project.toml", () => {
+        expect(installer.getProjectFilePath(path.join(fixtureDir, "PkgC"))).toEqual(path.join(fixtureDir, "PkgC", "JuliaProject.toml"))
+    })
+
+    it("Can determine project from JULIA_PROJECT", () => {
+        process.env["JULIA_PROJECT"] = path.join(fixtureDir, "PkgA")
+        expect(installer.getProjectFilePath()).toEqual(path.join(fixtureDir, "PkgA", "Project.toml"))
+    })
+
+    it("Can determine project from the current working directory", () => {
+        process.chdir(path.join(fixtureDir, "PkgA"));
+        expect(installer.getProjectFilePath()).toEqual("Project.toml")
+    })
+
+    it("Ignores JULIA_PROJECT when argument is used", () => {
+        process.env["JULIA_PROJECT"] = path.join(fixtureDir, "PkgB")
+        expect(installer.getProjectFilePath(path.join(fixtureDir, "PkgA"))).toEqual(path.join(fixtureDir, "PkgA", "Project.toml"))
+    })
+})
+
+describe("validJuliaCompatRange tests", () => {
+    it('Handles default caret specifier', () => {
+        expect(installer.validJuliaCompatRange("1")).toEqual(semver.validRange("^1"))
+        expect(installer.validJuliaCompatRange("1.2")).toEqual(semver.validRange("^1.2"))
+        expect(installer.validJuliaCompatRange("1.2.3")).toEqual(semver.validRange("^1.2.3"))
+
+        // TODO: Pkg.jl currently does not support pre-release entries in compat so ideally this would fail
+        expect(installer.validJuliaCompatRange("1.2.3-rc1")).toEqual(semver.validRange("^1.2.3-rc1"))
+    })
+
+    it('Handle surrounding whitespace', () => {
+        expect(installer.validJuliaCompatRange(" 1")).toEqual(semver.validRange("^1"))
+        expect(installer.validJuliaCompatRange("1 ")).toEqual(semver.validRange("^1"))
+        expect(installer.validJuliaCompatRange(" 1 ")).toEqual(semver.validRange("^1"))
+    })
+
+    it('Handles version ranges with specifiers', () => {
+        expect(installer.validJuliaCompatRange("^1.2.3")).toEqual(semver.validRange("^1.2.3"))
+        expect(installer.validJuliaCompatRange("~1.2.3")).toEqual(semver.validRange("~1.2.3"))
+        expect(installer.validJuliaCompatRange("=1.2.3")).toEqual(semver.validRange("=1.2.3"))
+        expect(installer.validJuliaCompatRange(">=1.2.3")).toEqual(">=1.2.3")
+        expect(installer.validJuliaCompatRange("≥1.2.3")).toEqual(">=1.2.3")
+        expect(installer.validJuliaCompatRange("<1.2.3")).toEqual("<1.2.3")
+    })
+
+    it('Handles whitespace after specifiers', () => {
+        expect(installer.validJuliaCompatRange("^ 1.2.3")).toBeNull()
+        expect(installer.validJuliaCompatRange("~ 1.2.3")).toBeNull()
+        expect(installer.validJuliaCompatRange("= 1.2.3")).toBeNull()
+        expect(installer.validJuliaCompatRange(">= 1.2.3")).toEqual(">=1.2.3")
+        expect(installer.validJuliaCompatRange("≥ 1.2.3")).toEqual(">=1.2.3")
+        expect(installer.validJuliaCompatRange("< 1.2.3")).toEqual("<1.2.3")
+    })
+
+    it('Handles hypen ranges', () => {
+        expect(installer.validJuliaCompatRange("1.2.3 - 4.5.6")).toEqual(semver.validRange("1.2.3 - 4.5.6"))
+        expect(installer.validJuliaCompatRange("1.2.3-rc1 - 4.5.6")).toEqual(semver.validRange("1.2.3-rc1 - 4.5.6"))
+        expect(installer.validJuliaCompatRange("1.2.3-rc1-4.5.6")).toEqual(semver.validRange("^1.2.3-rc1-4.5.6"))  // A version number and not a hypen range
+        expect(installer.validJuliaCompatRange("1.2.3-rc1 -4.5.6")).toBeNull()
+        expect(installer.validJuliaCompatRange("1.2.3-rc1- 4.5.6")).toBeNull()  // Whitespace separate version ranges
+    })
+
+    it("Returns null AND operator on version ranges", () => {
+        expect(installer.validJuliaCompatRange("")).toBeNull()
+        expect(installer.validJuliaCompatRange("1 2 3")).toBeNull()
+        expect(installer.validJuliaCompatRange("1- 2")).toBeNull()
+        expect(installer.validJuliaCompatRange("<1 <1")).toBeNull()
+        expect(installer.validJuliaCompatRange("< 1 < 1")).toBeNull()
+        expect(installer.validJuliaCompatRange("<  1 <  1")).toBeNull()
+    })
+
+    it('Returns null with invalid specifiers', () => {
+        expect(installer.validJuliaCompatRange("<=1.2.3")).toBeNull()
+        expect(installer.validJuliaCompatRange("≤1.2.3")).toBeNull()
+        expect(installer.validJuliaCompatRange("*")).toBeNull()
+    })
+
+    it("Handles OR operator on version ranges", () => {
+        expect(installer.validJuliaCompatRange("1, 2, 3")).toEqual(semver.validRange("^1 || ^2 || ^3"))
+        expect(installer.validJuliaCompatRange("1, 2 - 3, ≥ 4")).toEqual(semver.validRange("^1 || >=2 <=3 || >=4"))
+        expect(installer.validJuliaCompatRange(",")).toBeNull()
+    })
+})
+
+describe("readJuliaCompatRange tests", () => {
+    it('Can determine Julia compat entries', () => {
+        const toml = '[compat]\njulia = "1, ^1.1, ~1.2, >=1.3, 1.4 - 1.5"'
+        expect(installer.readJuliaCompatRange(toml)).toEqual(semver.validRange("^1 || ^1.1 || ~1.2 || >=1.3 || 1.4 - 1.5"))
+    })
+
+    it('Throws with invalid version ranges', () => {
+        expect(() => installer.readJuliaCompatRange('[compat]\njulia = ""')).toThrow("Invalid version range")
+        expect(() => installer.readJuliaCompatRange('[compat]\njulia = "1 2 3"')).toThrow("Invalid version range")
+    })
+
+    it('Handle missing compat entries', () => {
+        expect(installer.readJuliaCompatRange("")).toEqual("*")
+        expect(installer.readJuliaCompatRange("[compat]")).toEqual("*")
+
+    })
+})
 
 describe('version matching tests', () => {
     describe('specific versions', () => {
@@ -95,6 +224,34 @@ describe('version matching tests', () => {
             })
         })
     })
+
+    describe('julia compat versions', () => {
+        it('Understands "min"', () => {
+            let versions = ["1.6.7", "1.7.1-rc1", "1.7.1-rc2", "1.7.1", "1.7.2", "1.8.0"]
+            expect(installer.getJuliaVersion(versions, "min", false, "^1.7")).toEqual("1.7.1")
+            expect(installer.getJuliaVersion(versions, "min", true, "^1.7")).toEqual("1.7.1-rc1")
+
+            versions = ["1.6.7", "1.7.3-rc1", "1.7.3-rc2", "1.8.0"]
+            expect(installer.getJuliaVersion(versions, "min", false, "^1.7")).toEqual("1.8.0")
+            expect(installer.getJuliaVersion(versions, "min", true, "^1.7")).toEqual("1.7.3-rc1")
+
+            expect(installer.getJuliaVersion(versions, "min", false, "~1.7 || ~1.8 || ~1.9")).toEqual("1.8.0")
+            expect(installer.getJuliaVersion(versions, "min", true, "~1.7 || ~1.8 || ~1.9")).toEqual("1.7.3-rc1")
+            expect(installer.getJuliaVersion(versions, "min", false, "~1.8 || ~1.7 || ~1.9")).toEqual("1.8.0")
+            expect(installer.getJuliaVersion(versions, "min", true, "~1.8 || ~1.7 || ~1.9")).toEqual("1.7.3-rc1")
+
+            expect(installer.getJuliaVersion(versions, "min", false, "1.7 - 1.9")).toEqual("1.8.0")
+            expect(installer.getJuliaVersion(versions, "min", true, "1.7 - 1.9")).toEqual("1.7.3-rc1")
+
+            expect(installer.getJuliaVersion(versions, "min", true, "< 1.9.0")).toEqual("1.6.7")
+            expect(installer.getJuliaVersion(versions, "min", true, ">= 1.6.0")).toEqual("1.6.7")
+
+            // NPM's semver package treats "1.7" as "~1.7" instead of "^1.7" like Julia
+            expect(() => installer.getJuliaVersion(versions, "min", false, "1.7")).toThrow("Could not find a Julia version that matches")
+
+            expect(() => installer.getJuliaVersion(versions, "min", true, "")).toThrow("Julia project file does not specify a compat for Julia")
+        })
+    })
 })
 
 describe('installer tests', () => {

action.yml

@@ -17,6 +17,10 @@ inputs:
     description: 'Display InteractiveUtils.versioninfo() after installing'
     required: false
     default: 'false'
+  project:
+    description: 'The path to the project directory or file to use when resolving some versions (e.g. min)'
+    required: false
+    default: ''  # Special value which fallsback to using JULIA_PROJECT if defined, otherwise "."
 outputs:
   julia-version:
     description: 'The installed Julia version. May vary from the version input if a version range was given as input.'

lib/installer.js

@@ -34,6 +34,9 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.getJuliaVersionInfo = getJuliaVersionInfo;
 exports.getJuliaVersions = getJuliaVersions;
+exports.getProjectFilePath = getProjectFilePath;
+exports.validJuliaCompatRange = validJuliaCompatRange;
+exports.readJuliaCompatRange = readJuliaCompatRange;
 exports.getJuliaVersion = getJuliaVersion;
 exports.getFileInfo = getFileInfo;
 exports.getDownloadURL = getDownloadURL;
@@ -48,6 +51,7 @@ const os = __importStar(require("os"));
 const path = __importStar(require("path"));
 const retry = require("async-retry");
 const semver = __importStar(require("semver"));
+const toml = __importStar(require("toml"));
 const LTS_VERSION = '1.6';
 const MAJOR_VERSION = '1'; // Could be deduced from versions.json
 // Translations between actions input and Julia arch names
@@ -112,20 +116,106 @@ function getJuliaVersions(versionInfo) {
         return versions;
     });
 }
-function getJuliaVersion(availableReleases, versionInput, includePrerelease = false) {
+/**
+ * @returns The path to the Julia project file
+ */
+function getProjectFilePath(projectInput = "") {
+    let projectFilePath = "";
+    // Default value for projectInput
+    if (!projectInput) {
+        projectInput = process.env.JULIA_PROJECT || ".";
+    }
+    if (fs.existsSync(projectInput) && fs.lstatSync(projectInput).isFile()) {
+        projectFilePath = projectInput;
+    }
+    else {
+        for (let projectFilename of ["JuliaProject.toml", "Project.toml"]) {
+            let p = path.join(projectInput, projectFilename);
+            if (fs.existsSync(p) && fs.lstatSync(p).isFile()) {
+                projectFilePath = p;
+                break;
+            }
+        }
+    }
+    if (!projectFilePath) {
+        throw new Error(`Unable to locate project file with project input: ${projectInput}`);
+    }
+    return projectFilePath;
+}
+/**
+ * @returns A valid NPM semver range from a Julia compat range or null if it's not valid
+ */
+function validJuliaCompatRange(compatRange) {
+    let ranges = [];
+    for (let range of compatRange.split(",")) {
+        range = range.trim();
+        // An empty range isn't supported by Julia
+        if (!range) {
+            return null;
+        }
+        // NPM's semver doesn't understand unicode characters such as `≥` so we'll convert to alternatives
+        range = range.replace("≥", ">=").replace("≤", "<=");
+        // Cleanup whitespace. Julia only allows whitespace between the specifier and version with certain specifiers
+        range = range.replace(/\s+/g, " ").replace(/(?<=(>|>=|≥|<)) (?=\d)/g, "");
+        if (!semver.validRange(range) || range.split(/(?<! -) (?!- )/).length > 1 || range.startsWith("<=") || range === "*") {
+            return null;
+        }
+        else if (range.search(/^\d/) === 0 && !range.includes(" ")) {
+            // Compat version is just a basic version number (e.g. 1.2.3). Since Julia's Pkg.jl's uses caret
+            // as the default specifier (e.g. `1.2.3 == ^1.2.3`) and NPM's semver uses tilde as the default
+            // specifier (e.g. `1.2.3 == 1.2.x == ~1.2.3`) we will introduce the caret specifier to ensure the
+            // orignal intent is respected.
+            // https://pkgdocs.julialang.org/v1/compatibility/#Version-specifier-format
+            // https://github.com/npm/node-semver#x-ranges-12x-1x-12-
+            range = "^" + range;
+        }
+        ranges.push(range);
+    }
+    return semver.validRange(ranges.join(" || "));
+}
+/**
+ * @returns An array of version ranges compatible with the Julia project
+ */
+function readJuliaCompatRange(projectFileContent) {
+    var _a;
+    let compatRange;
+    let meta = toml.parse(projectFileContent);
+    if (((_a = meta.compat) === null || _a === void 0 ? void 0 : _a.julia) !== undefined) {
+        compatRange = validJuliaCompatRange(meta.compat.julia);
+    }
+    else {
+        compatRange = "*";
+    }
+    if (!compatRange) {
+        throw new Error(`Invalid version range found in Julia compat: ${compatRange}`);
+    }
+    return compatRange;
+}
+function getJuliaVersion(availableReleases, versionInput, includePrerelease = false, juliaCompatRange = "") {
+    // Note: `juliaCompatRange` is ignored unless `versionInput` is `min`
+    let version;
     if (semver.valid(versionInput) == versionInput || versionInput.endsWith('nightly')) {
         // versionInput is a valid version or a nightly version, use it directly
-        return versionInput;
+        version = versionInput;
     }
-    if (versionInput == 'lts') {
-        return getJuliaVersion(availableReleases, LTS_VERSION, false);
+    else if (versionInput == "min") {
+        // Resolve "min" to the minimum supported Julia version compatible with the project file
+        if (!juliaCompatRange) {
+            throw new Error('Unable to use version "min" when the Julia project file does not specify a compat for Julia');
+        }
+        version = semver.minSatisfying(availableReleases, juliaCompatRange, { includePrerelease });
     }
-    if (versionInput == 'pre') {
-        return getJuliaVersion(availableReleases, MAJOR_VERSION, true);
+    else if (versionInput == "lts") {
+        version = semver.maxSatisfying(availableReleases, LTS_VERSION, { includePrerelease: false });
     }
-    // Use the highest available version that matches versionInput
-    let version = semver.maxSatisfying(availableReleases, versionInput, { includePrerelease });
-    if (version == null) {
+    else if (versionInput == "pre") {
+        version = semver.maxSatisfying(availableReleases, MAJOR_VERSION, { includePrerelease: true });
+    }
+    else {
+        // Use the highest available version that matches versionInput
+        version = semver.maxSatisfying(availableReleases, versionInput, { includePrerelease });
+    }
+    if (!version) {
         throw new Error(`Could not find a Julia version that matches ${versionInput}`);
     }
     // GitHub tags start with v, remove it

lib/setup-julia.js

@@ -72,6 +72,7 @@ function run() {
             const versionInput = core.getInput('version').trim();
             const includePrereleases = core.getInput('include-all-prereleases').trim() == 'true';
             const originalArchInput = core.getInput('arch').trim();
+            const 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.
@@ -100,9 +101,15 @@ function run() {
             // before we index into the `archSynonyms` dict.
             const arch = archSynonyms[processedArchInput.toLowerCase()];
             core.debug(`Mapped the "arch" from ${processedArchInput} to ${arch}`);
+            // Determine the Julia compat ranges as specified by the Project.toml only for special versions that require them.
+            let juliaCompatRange = "";
+            if (versionInput === "min") {
+                const projectFilePath = installer.getProjectFilePath(projectInput);
+                juliaCompatRange = installer.readJuliaCompatRange(fs.readFileSync(projectFilePath).toString());
+            }
             const versionInfo = yield installer.getJuliaVersionInfo();
             const availableReleases = yield installer.getJuliaVersions(versionInfo);
-            const version = installer.getJuliaVersion(availableReleases, versionInput, includePrereleases);
+            const version = installer.getJuliaVersion(availableReleases, versionInput, includePrereleases, juliaCompatRange);
             core.debug(`selected Julia version: ${arch}/${version}`);
             core.setOutput('julia-version', version);
             // Search in cache

package.json

@@ -26,7 +26,8 @@
     "@actions/io": "^1.1.3",
     "@actions/tool-cache": "^2.0.1",
     "async-retry": "^1.3.3",
-    "semver": "^7.6.3"
+    "semver": "^7.6.3",
+    "toml": "^3.0.0"
   },
   "devDependencies": {
     "@types/async-retry": "^1.4.8",

src/installer.ts

@@ -9,6 +9,7 @@ import * as path from 'path'
 import retry = require('async-retry')
 
 import * as semver from 'semver'
+import * as toml from 'toml'
 
 const LTS_VERSION = '1.6'
 const MAJOR_VERSION = '1' // Could be deduced from versions.json
@@ -79,23 +80,116 @@ export async function getJuliaVersions(versionInfo): Promise<string[]> {
     return versions
 }
 
-export function getJuliaVersion(availableReleases: string[], versionInput: string, includePrerelease: boolean = false): string {
+/**
+ * @returns The path to the Julia project file
+ */
+export function getProjectFilePath(projectInput: string = ""): string {
+    let projectFilePath: string = ""
+
+    // Default value for projectInput
+    if (!projectInput) {
+        projectInput = process.env.JULIA_PROJECT || "."
+    }
+
+    if (fs.existsSync(projectInput) && fs.lstatSync(projectInput).isFile()) {
+        projectFilePath = projectInput
+    } else {
+        for (let projectFilename of ["JuliaProject.toml", "Project.toml"]) {
+            let p = path.join(projectInput, projectFilename)
+            if (fs.existsSync(p) && fs.lstatSync(p).isFile()) {
+                projectFilePath = p
+                break
+            }
+        }
+    }
+
+    if (!projectFilePath) {
+        throw new Error(`Unable to locate project file with project input: ${projectInput}`)
+    }
+
+    return projectFilePath
+}
+
+/**
+ * @returns A valid NPM semver range from a Julia compat range or null if it's not valid
+ */
+export function validJuliaCompatRange(compatRange: string): string | null {
+    let ranges: Array<string> = []
+    for(let range of compatRange.split(",")) {
+        range = range.trim()
+
+        // An empty range isn't supported by Julia
+        if (!range) {
+            return null
+        }
+
+        // NPM's semver doesn't understand unicode characters such as `≥` so we'll convert to alternatives
+        range = range.replace("≥", ">=").replace("≤", "<=")
+
+        // Cleanup whitespace. Julia only allows whitespace between the specifier and version with certain specifiers
+        range = range.replace(/\s+/g, " ").replace(/(?<=(>|>=|≥|<)) (?=\d)/g, "")
+
+        if (!semver.validRange(range) || range.split(/(?<! -) (?!- )/).length > 1 || range.startsWith("<=") || range === "*") {
+            return null
+        } else if (range.search(/^\d/) === 0 && !range.includes(" ")) {
+            // Compat version is just a basic version number (e.g. 1.2.3). Since Julia's Pkg.jl's uses caret
+            // as the default specifier (e.g. `1.2.3 == ^1.2.3`) and NPM's semver uses tilde as the default
+            // specifier (e.g. `1.2.3 == 1.2.x == ~1.2.3`) we will introduce the caret specifier to ensure the
+            // orignal intent is respected.
+            // https://pkgdocs.julialang.org/v1/compatibility/#Version-specifier-format
+            // https://github.com/npm/node-semver#x-ranges-12x-1x-12-
+            range = "^" + range
+        }
+
+        ranges.push(range)
+    }
+
+    return semver.validRange(ranges.join(" || "))
+}
+
+/**
+ * @returns An array of version ranges compatible with the Julia project
+ */
+export function readJuliaCompatRange(projectFileContent: string): string {
+    let compatRange: string | null
+    let meta = toml.parse(projectFileContent)
+
+    if (meta.compat?.julia !== undefined) {
+        compatRange = validJuliaCompatRange(meta.compat.julia)
+    } else {
+        compatRange = "*"
+    }
+
+    if (!compatRange) {
+        throw new Error(`Invalid version range found in Julia compat: ${compatRange}`)
+    }
+
+    return compatRange
+}
+
+export function getJuliaVersion(availableReleases: string[], versionInput: string, includePrerelease: boolean = false, juliaCompatRange: string = ""): string {
+    // Note: `juliaCompatRange` is ignored unless `versionInput` is `min`
+    let version: string | null
+
     if (semver.valid(versionInput) == versionInput || versionInput.endsWith('nightly')) {
         // versionInput is a valid version or a nightly version, use it directly
-        return versionInput
+        version = versionInput
+    } else if (versionInput == "min") {
+        // Resolve "min" to the minimum supported Julia version compatible with the project file
+        if (!juliaCompatRange) {
+            throw new Error('Unable to use version "min" when the Julia project file does not specify a compat for Julia')
+        }
+        version = semver.minSatisfying(availableReleases, juliaCompatRange, {includePrerelease})
+    } else if (versionInput == "lts") {
+        version = semver.maxSatisfying(availableReleases, LTS_VERSION, { includePrerelease: false });
+    } else if (versionInput == "pre") {
+        version = semver.maxSatisfying(availableReleases, MAJOR_VERSION, { includePrerelease: true });
+    } else {
+        // Use the highest available version that matches versionInput
+        version = semver.maxSatisfying(availableReleases, versionInput, {includePrerelease})
     }
 
-    if (versionInput == 'lts') {
-        return getJuliaVersion(availableReleases, LTS_VERSION, false)
-    }
-
-    if (versionInput == 'pre') {
-        return getJuliaVersion(availableReleases, MAJOR_VERSION, true)
-    }
-
-    // Use the highest available version that matches versionInput
-    let version = semver.maxSatisfying(availableReleases, versionInput, {includePrerelease})
-    if (version == null) {
+    if (!version) {
         throw new Error(`Could not find a Julia version that matches ${versionInput}`)
     }
 

src/setup-julia.ts

@@ -44,6 +44,7 @@ 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 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 }}`.
@@ -74,9 +75,16 @@ async function run() {
         const arch = archSynonyms[processedArchInput.toLowerCase()]
         core.debug(`Mapped the "arch" from ${processedArchInput} to ${arch}`)
 
+        // Determine the Julia compat ranges as specified by the Project.toml only for special versions that require them.
+        let juliaCompatRange: string = "";
+        if (versionInput === "min") {
+            const projectFilePath = installer.getProjectFilePath(projectInput)
+            juliaCompatRange = installer.readJuliaCompatRange(fs.readFileSync(projectFilePath).toString())
+        }
+
         const versionInfo = await installer.getJuliaVersionInfo()
         const availableReleases = await installer.getJuliaVersions(versionInfo)
-        const version = installer.getJuliaVersion(availableReleases, versionInput, includePrereleases)
+        const version = installer.getJuliaVersion(availableReleases, versionInput, includePrereleases, juliaCompatRange)
         core.debug(`selected Julia version: ${arch}/${version}`)
         core.setOutput('julia-version', version)