add option to set config BUNDLE_FROZEN for bundler install

* tried to remain flexible to allow other options to be set in the future

Author: KyFaSt

.github/workflows/test.yml

@@ -419,6 +419,94 @@ jobs:
       - name: C:/msys64/mingw64/bin/gcc.exe not installed
         run: ruby -e "abort if File.exist?('C:/msys64/mingw64/bin/gcc.exe')"
 
+  testBundleFrozen:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+        ruby: [ '3.1', '3.2', '3.3', '3.4' ]
+    name: "Test bundle-frozen on ${{ matrix.os }} with Ruby ${{ matrix.ruby }}"
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@v5
+    - name: Create test Gemfile with locked dependencies
+      shell: bash
+      run: |
+        cat > Gemfile <<'EOF'
+        source 'https://rubygems.org'
+        gem 'rake', '~> 13.0'
+        gem 'minitest', '~> 5.16'
+        EOF
+    - name: Generate Gemfile.lock
+      shell: bash
+      run: |
+        gem install bundler
+        bundle lock
+    - name: Display Gemfile.lock
+      shell: bash
+      run: cat Gemfile.lock
+    - uses: ./
+      with:
+        ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
+        bundle-frozen: true
+    - name: Verify frozen config was set
+      shell: bash
+      run: |
+        FROZEN_VALUE=$(bundle config frozen)
+        echo "Bundle frozen config: $FROZEN_VALUE"
+        if echo "$FROZEN_VALUE" | grep -q "true"; then
+          echo "✓ Bundle frozen config is set to true"
+        else
+          echo "Error: Bundle frozen config was not set to 'true'"
+          exit 1
+        fi
+    - name: Verify bundle install succeeded with frozen lockfile
+      shell: bash
+      run: |
+        bundle exec ruby -v
+        echo "✓ Bundle install with frozen lockfile succeeded"
+    - name: Test that modifying Gemfile causes failure with bundle-frozen
+      shell: bash
+      run: |
+        echo "gem 'json', '~> 2.6'" >> Gemfile
+        if bundle install 2>&1 | grep -q "frozen"; then
+          echo "✓ Bundle correctly detected frozen lockfile violation"
+        else
+          echo "Warning: Expected bundle install to fail or warn about frozen lockfile"
+        fi
+        git checkout Gemfile
+
+  testBundleNotFrozen:
+    name: "Test without bundle-frozen (control)"
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v5
+    - name: Create test Gemfile
+      run: |
+        cat > Gemfile <<'EOF'
+        source 'https://rubygems.org'
+        gem 'rake', '~> 13.0'
+        EOF
+    - uses: ./
+      with:
+        ruby-version: '3.4'
+        bundler-cache: true
+        bundle-frozen: false
+    - name: Verify frozen config was not set
+      run: |
+        FROZEN_VALUE=$(bundle config frozen)
+        echo "Bundle frozen config: $FROZEN_VALUE"
+        if echo "$FROZEN_VALUE" | grep -q "true"; then
+          echo "Error: Bundle frozen config should not be set when bundle-frozen is false"
+          exit 1
+        fi
+        echo "✓ Bundle frozen config is not set to true (as expected)"
+    - name: Verify bundle install succeeded
+      run: |
+        bundle exec ruby -v
+        echo "✓ Bundle install succeeded without frozen flag"
+
   lint:
     runs-on: ubuntu-22.04
     steps:

README.md

@@ -190,6 +190,20 @@ This caching speeds up installing gems significantly and avoids too many request
 It needs a `Gemfile` (or `$BUNDLE_GEMFILE` or `gems.rb`) under the [`working-directory`](#working-directory).  
 If there is a `Gemfile.lock` (or `$BUNDLE_GEMFILE.lock` or `gems.locked`), `bundle config --local deployment true` is used.
 
+#### bundle-frozen
+
+When using `bundler-cache: true`, you can optionally set `bundle-frozen: true` to enforce that the `Gemfile.lock` is not modified during `bundle install`:
+```yaml
+    - uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: '3.4'
+        bundler-cache: true
+        bundle-frozen: true
+```
+
+This runs `bundle config --local frozen true` before bundle install, which disallows changes to the Gemfile.lock.
+This is useful in CI to ensure the lockfile is up to date and prevents accidental modifications.
+
 To use a `Gemfile` which is not at the root or has a different name, set `BUNDLE_GEMFILE` in the `env` at the job level
 as shown in the [example](#matrix-of-gemfiles).
 

action.yml

@@ -25,6 +25,9 @@ inputs:
   bundler-cache:
     description: 'Run "bundle install", and cache the result automatically. Either true or false.'
     default: 'false'
+  bundle-frozen:
+    description: 'Run "bundle config --local frozen true" before bundle install to disallow changes to the Gemfile.lock. Either true or false.'
+    default: 'false'
   working-directory:
     description: 'The working directory to use for resolving paths for .ruby-version, .tool-versions, mise.toml and Gemfile.lock.'
   cache-version:

bundler.js

@@ -137,7 +137,28 @@ export async function installBundler(bundlerVersionInput, rubygemsInputSet, lock
   return bundlerVersion
 }
 
-export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVersion, bundlerVersion, cacheVersion) {
+async function applyBundleConfig(configOptions, envOptions = {}) {
+  // Apply bundle config settings based on input options
+  // This function makes it easy to add new bundle config options in the future
+  const configs = []
+  
+  if (configOptions.frozen === 'true') {
+    configs.push({ name: 'frozen', value: 'true', description: 'frozen' })
+  }
+  
+  // Add more config options here as needed in the future
+  // Example:
+  // if (configOptions.jobs) {
+  //   configs.push({ name: 'jobs', value: configOptions.jobs, description: 'jobs' })
+  // }
+  
+  for (const config of configs) {
+    console.log(`Setting bundle config ${config.description} to ${config.value}`)
+    await exec.exec('bundle', ['config', '--local', config.name, config.value], envOptions)
+  }
+}
+
+export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVersion, bundlerVersion, cacheVersion, bundleFrozen = 'false') {
   if (gemfile === null) {
     console.log('Could not determine gemfile path, skipping "bundle install" and caching')
     return false
@@ -158,6 +179,9 @@ export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVer
 
   await exec.exec('bundle', ['config', '--local', 'path', bundleCachePath], envOptions)
 
+  // Apply bundle config options
+  await applyBundleConfig({ frozen: bundleFrozen }, envOptions)
+
   if (fs.existsSync(lockFile)) {
     await exec.exec('bundle', ['config', '--local', 'deployment', 'true'], envOptions)
   } else {
@@ -196,6 +220,7 @@ export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVer
 
   // Number of jobs should scale with runner, up to a point
   const jobs = Math.min(os.availableParallelism(), 8)
+  
   // Always run 'bundle install' to list the gems
   await exec.exec('bundle', ['install', '--jobs', `${jobs}`])
 

dist/index.js

@@ -14,6 +14,7 @@ const inputDefaults = {
   'rubygems': 'default',
   'bundler': 'Gemfile.lock',
   'bundler-cache': 'false',
+  'bundle-frozen': 'false',
   'working-directory': '.',
   'cache-version': bundler.DEFAULT_CACHE_VERSION,
   'self-hosted': 'false',
@@ -97,8 +98,13 @@ export async function setupRuby(options = {}) {
   }
 
   if (inputs['bundler-cache'] === 'true') {
+    // Note: To add new bundle config options in the future:
+    // 1. Add the input to action.yml
+    // 2. Add it to inputDefaults above
+    // 3. Pass it to bundleInstall (or create a bundleConfig object to pass multiple options)
+    // 4. Update the applyBundleConfig function in bundler.js
     await common.time('bundle install', async () =>
-      bundler.bundleInstall(gemfile, lockFile, platform, engine, version, bundlerVersion, inputs['cache-version']))
+      bundler.bundleInstall(gemfile, lockFile, platform, engine, version, bundlerVersion, inputs['cache-version'], inputs['bundle-frozen']))
   }
 
   core.setOutput('ruby-prefix', rubyPrefix)