Use Bundler 1 on Ruby 2.3

* At least until there is a new Bundler 2 release fixing this.
* Fixes #51

Author: eregon

README.md

@@ -112,7 +112,7 @@ and the [condition and expression syntax](https://help.github.com/en/actions/ref
 
 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.
 

dist/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') {