cache version option

README.md

@@ -180,6 +180,20 @@ When there is no lockfile, one is generated with `bundle lock`, which is the sam
 In other words, it works exactly like `bundle install`.
 The hash of the generated lockfile is then used for caching, which is the only correct approach.
 
+#### Dealing with a corrupted cache
+
+In some rare scenarios (like using gems with C extensions whose functionality depends on libraries found on the system
+at the time of the gem's build) it may be necessary to ignore contents of the cache and get and build all the gems anew.
+In order to achieve this, set the `cache-version` option to any value other than `0` (or change it to a new unique value
+if you have already used it before.)
+
+```yaml
+    - uses: ruby/setup-ruby@v1
+      with:
+        bundler-cache: true
+        cache-version: 1
+```
+
 #### Caching `bundle install` manually
 
 It is also possible to cache gems manually, but this is not recommended because it is verbose and *very difficult* to do correctly.

action.yml

@@ -24,6 +24,12 @@ inputs:
     description: 'The working directory to use for resolving paths for .ruby-version, .tool-versions and Gemfile.lock.'
     required: false
     default: '.'
+  cache-version:
+    description: |
+      Arbitrary string that will be added to the cache key of the bundler cache. Set or change it if you need
+      to invalidate the cache.
+    required: false
+    default: '0'
 outputs:
   ruby-prefix:
     description: 'The prefix of the installed ruby'

bundler.js

@@ -5,6 +5,8 @@ const exec = require('@actions/exec')
 const cache = require('@actions/cache')
 const common = require('./common')
 
+export const DEFAULT_CACHE_VERSION = '0'
+
 // The returned gemfile is guaranteed to exist, the lockfile might not exist
 export function detectGemfiles() {
   const gemfilePath = process.env['BUNDLE_GEMFILE'] || 'Gemfile'
@@ -95,7 +97,7 @@ export async function installBundler(bundlerVersionInput, lockFile, platform, ru
   return bundlerVersion
 }
 
-export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVersion, bundlerVersion) {
+export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVersion, bundlerVersion, cacheVersion) {
   if (gemfile === null) {
     console.log('Could not determine gemfile path, skipping "bundle install" and caching')
     return false
@@ -128,7 +130,7 @@ export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVer
 
   // cache key
   const paths = [cachePath]
-  const baseKey = await computeBaseKey(platform, engine, rubyVersion, lockFile)
+  const baseKey = await computeBaseKey(platform, engine, rubyVersion, lockFile, cacheVersion)
   const key = `${baseKey}-${await common.hashFile(lockFile)}`
   // If only Gemfile.lock changes we can reuse part of the cache, and clean old gem versions below
   const restoreKeys = [`${baseKey}-`]
@@ -177,8 +179,9 @@ export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVer
   return true
 }
 
-async function computeBaseKey(platform, engine, version, lockFile) {
-  let key = `setup-ruby-bundler-cache-v3-${platform}-${engine}-${version}`
+async function computeBaseKey(platform, engine, version, lockFile, cacheVersion) {
+  const cacheVersionSuffix = DEFAULT_CACHE_VERSION === cacheVersion ? '' : `-cachever:${cacheVersion}`
+  let key = `setup-ruby-bundler-cache-v3-${platform}-${engine}-${version}${cacheVersionSuffix}`
 
   if (engine !== 'jruby' && common.isHeadVersion(version)) {
     let revision = '';

index.js

@@ -12,6 +12,7 @@ const inputDefaults = {
   'bundler': 'default',
   'bundler-cache': 'true',
   'working-directory': '.',
+  'cache-version': bundler.DEFAULT_CACHE_VERSION,
 }
 
 // entry point when this action is run on its own
@@ -67,7 +68,7 @@ export async function setupRuby(options = {}) {
 
     if (inputs['bundler-cache'] === 'true') {
       await common.measure('bundle install', async () =>
-          bundler.bundleInstall(gemfile, lockFile, platform, engine, version, bundlerVersion))
+          bundler.bundleInstall(gemfile, lockFile, platform, engine, version, bundlerVersion, inputs['cache-version']))
     }
   }