Use Bundler 1 on Ruby 2.3

* At least until there is a new Bundler 2 release fixing this.
* Fixes https://github.com/ruby/setup-ruby/issues/51

README.md

@@ -64,13 +64,14 @@ jobs:
     - uses: actions/checkout@v2
     - uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.6
-    - run: ruby -v
+        ruby-version: 2.6 # Not needed with a .ruby-version file
+    - run: bundle install
+    - run: bundle exec rake
 ```
 
 ### Matrix
 
-This matrix tests all stable releases of MRI, JRuby and TruffleRuby on Ubuntu and macOS.
+This matrix tests all stable releases and `head` versions of MRI, JRuby and TruffleRuby on Ubuntu and macOS.
 
 ```yaml
 name: My workflow
@@ -80,17 +81,23 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ ubuntu-latest, macos-latest ]
-        ruby: [ 2.4, 2.5, 2.6, 2.7, jruby, truffleruby ]
-    runs-on: ${{ matrix.os }}
+        os: [ubuntu, macos]
+        ruby: [2.5, 2.6, 2.7, head, debug, jruby, jruby-head, truffleruby, truffleruby-head]
+    runs-on: ${{ matrix.os }}-latest
+    continue-on-error: ${{ endsWith(matrix.ruby, 'head') || matrix.ruby == 'debug' }}
     steps:
     - uses: actions/checkout@v2
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
-    - run: ruby -v
+    - run: bundle install
+    - run: bundle exec rake
 ```
 
+See the GitHub Actions documentation for more details about the
+[workflow syntax](https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions)
+and the [condition and expression syntax](https://help.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions).
+
 ### Supported Version Syntax
 
 * engine-version like `ruby-2.6.5` and `truffleruby-19.3.0`
@@ -105,7 +112,7 @@ jobs:
 
 By default, if there is a `Gemfile.lock` file with a `BUNDLED WITH` section,
 the latest version of Bundler with the same major version will be installed.
-Otherwise, the latest Bundler version is installed (except for Ruby 2.2 where only Bundler 1 is supported).
+Otherwise, the latest Bundler version is installed (except for Ruby 2.2 and 2.3 where only Bundler 1 is supported).
 
 This behavior can be customized, see [action.yml](action.yml) for details about the `bundler` input.
 
@@ -122,8 +129,9 @@ You can cache the installed gems with these two steps:
           bundle-use-ruby-${{ matrix.os }}-${{ matrix.ruby }}-
     - name: bundle install
       run: |
+        bundle config deployment true
         bundle config path vendor/bundle
-        bundle install --jobs 4 --retry 3
+        bundle install --jobs 4
 ```
 
 When using a single OS, replace `${{ matrix.os }}` with the OS.  

dist/index.js

@@ -1127,15 +1127,20 @@ async function installBundler(platform, rubyPrefix, engine, rubyVersion) {
     bundlerVersion = '2'
   }
 
-  if (rubyVersion.startsWith('2.2')) {
-    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby 2.2')
-    bundlerVersion = '1'
-  } else if (/^\d+/.test(bundlerVersion)) {
+  if (/^\d+/.test(bundlerVersion)) {
     // OK
   } else {
     throw new Error(`Cannot parse bundler input: ${bundlerVersion}`)
   }
 
+  if (rubyVersion.startsWith('2.2')) {
+    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby 2.2')
+    bundlerVersion = '1'
+  } else if (rubyVersion.startsWith('2.3')) {
+    console.log('Ruby 2.3 has a bug with Bundler 2 (https://github.com/rubygems/rubygems/issues/3570), using Bundler 1 instead on Ruby 2.3')
+    bundlerVersion = '1'
+  }
+
   if (engine === 'ruby' && common.isHeadVersion(rubyVersion) && bundlerVersion === '2') {
     console.log(`Using Bundler 2 shipped with ${engine}-${rubyVersion}`)
   } else if (engine === 'truffleruby' && bundlerVersion === '1') {

index.js

@@ -156,15 +156,20 @@ async function installBundler(platform, rubyPrefix, engine, rubyVersion) {
     bundlerVersion = '2'
   }
 
-  if (rubyVersion.startsWith('2.2')) {
-    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby 2.2')
-    bundlerVersion = '1'
-  } else if (/^\d+/.test(bundlerVersion)) {
+  if (/^\d+/.test(bundlerVersion)) {
     // OK
   } else {
     throw new Error(`Cannot parse bundler input: ${bundlerVersion}`)
   }
 
+  if (rubyVersion.startsWith('2.2')) {
+    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby 2.2')
+    bundlerVersion = '1'
+  } else if (rubyVersion.startsWith('2.3')) {
+    console.log('Ruby 2.3 has a bug with Bundler 2 (https://github.com/rubygems/rubygems/issues/3570), using Bundler 1 instead on Ruby 2.3')
+    bundlerVersion = '1'
+  }
+
   if (engine === 'ruby' && common.isHeadVersion(rubyVersion) && bundlerVersion === '2') {
     console.log(`Using Bundler 2 shipped with ${engine}-${rubyVersion}`)
   } else if (engine === 'truffleruby' && bundlerVersion === '1') {