Read Ruby version from Gemfile.lock

.github/workflows/test.yml

@@ -217,6 +217,30 @@ jobs:
         rubygems: 3.2.3
     - run: gem --version | grep -F "3.3.3"
 
+  testRubyVersionFromGemfile:
+    name: "Test RUBY VERSION from Gemfile.lock"
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/ruby-version.gemfile
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./
+        with:
+          ruby-version: gemfile
+      - run: ruby --version | grep -F "3.3.1"
+
+  testRubyEngineVersionFromGemfile:
+    name: "Test RUBY VERSION from Gemfile.lock"
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/ruby-version-engine.gemfile
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./
+        with:
+          ruby-version: gemfile
+      - run: ruby --version | grep -F "truffleruby 24.0.1, like ruby 3.2.2"
+
   testUseBundlerFromRubyGemsUpdate:
     name: "Test rubygems: version uses the Bundler installed by the rubygems update"
     runs-on: ubuntu-latest

README.md

@@ -135,7 +135,8 @@ and the [condition and expression syntax](https://help.github.com/en/actions/ref
 * engine only like `ruby` and `truffleruby`, uses the latest stable release of that implementation
 * `.ruby-version` reads from the project's `.ruby-version` file
 * `.tool-versions` reads from the project's `.tool-versions` file
-* If the `ruby-version` input is not specified, `.ruby-version` is tried first, followed by `.tool-versions`
+* `gemfile` reads from the project's `Gemfile.lock` file
+* If the `ruby-version` input is not specified, `.ruby-version` is tried first, followed by `.tool-versions`, then `Gemfile.lock`.
 
 ### Working Directory
 

action.yml

@@ -6,7 +6,7 @@ branding:
   icon: download
 inputs:
   ruby-version:
-    description: 'Engine and version to use, see the syntax in the README. Reads from .ruby-version or .tool-versions if unset.'
+    description: 'Engine and version to use, see the syntax in the README. When not set, it tries to read the version from .ruby-version, .tool-versions or Gemfile.lock.'
     default: 'default'
   rubygems:
     description: |

gemfiles/ruby-version-engine.gemfile

@@ -0,0 +1,3 @@
+source 'https://rubygems.org'
+
+ruby "3.2.2", engine: "truffleruby", engine_version: "24.0.1"

gemfiles/ruby-version-engine.gemfile.lock

@@ -0,0 +1,14 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+
+PLATFORMS
+  aarch64-darwin
+
+DEPENDENCIES
+
+RUBY VERSION
+   ruby 3.2.2p0 (truffleruby 24.0.1)
+
+BUNDLED WITH
+   2.4.10

gemfiles/ruby-version.gemfile

@@ -0,0 +1,3 @@
+source 'https://rubygems.org'
+
+ruby "3.3.1"

gemfiles/ruby-version.gemfile.lock

@@ -0,0 +1,15 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+
+PLATFORMS
+  arm64-darwin-23
+  ruby
+
+DEPENDENCIES
+
+RUBY VERSION
+   ruby 3.3.1p55
+
+BUNDLED WITH
+   2.5.9

index.js

@@ -105,14 +105,36 @@ export async function setupRuby(options = {}) {
   core.setOutput('ruby-prefix', rubyPrefix)
 }
 
+function readRubyVersionFromGemfileLock(lockFile) {
+  if (lockFile !== null && fs.existsSync(lockFile)) {
+    const contents = fs.readFileSync(lockFile, 'utf8')
+    const lines = contents.split(/\r?\n/)
+    const rubyVersionLine = lines.findIndex(line => /^RUBY VERSION$/.test(line.trim()))
+    if (rubyVersionLine !== -1) {
+      const nextLine = lines[rubyVersionLine+1]
+      if (nextLine) {
+        const rubyVersion = nextLine.trim()
+        if (rubyVersion.includes('(')) { // Alternative engine
+          return rubyVersion.match(/\(([^)]+)\)/)[1].replace(' ', '-')
+        } else {
+          return rubyVersion.replace(' ', '-').replace(/p\d+$/, '') // Strip off patchlevel
+        }
+      }
+    }
+  }
+  return null
+}
+
 function parseRubyEngineAndVersion(rubyVersion) {
   if (rubyVersion === 'default') {
     if (fs.existsSync('.ruby-version')) {
       rubyVersion = '.ruby-version'
     } else if (fs.existsSync('.tool-versions')) {
       rubyVersion = '.tool-versions'
+    } else if (fs.existsSync('Gemfile.lock')) {
+      rubyVersion = 'gemfile'
     } else {
-      throw new Error('input ruby-version needs to be specified if no .ruby-version or .tool-versions file exists')
+      throw new Error('input ruby-version needs to be specified if there is no Ruby version in .ruby-version, .tool-versions or Gemfile.lock')
     }
   }
 
@@ -124,6 +146,12 @@ function parseRubyEngineAndVersion(rubyVersion) {
     const rubyLine = toolVersions.split(/\r?\n/).filter(e => /^ruby\s/.test(e))[0]
     rubyVersion = rubyLine.match(/^ruby\s+(.+)$/)[1]
     console.log(`Using ${rubyVersion} as input from file .tool-versions`)
+  } else if (rubyVersion === 'gemfile') { // Read from Gemfile.lock
+    rubyVersion = readRubyVersionFromGemfileLock('Gemfile.lock')
+    if (rubyVersion === null) {
+      throw new Error('input ruby-version needs to be specified if there is no Ruby version in .ruby-version, .tool-versions or Gemfile.lock')
+    }
+    console.log(`Using ${rubyVersion} as input from Gemfile.lock`)
   }
 
   let engine, version
@@ -137,6 +165,8 @@ function parseRubyEngineAndVersion(rubyVersion) {
     [engine, version] = common.partition(rubyVersion, '-')
   }
 
+  console.log(`Using ruby engine ${engine} and version ${version}`)
+
   return [engine, version]
 }