Add test checking using an exact Bundler version works

.github/workflows/test.yml

@@ -102,6 +102,17 @@ jobs:
       if: startsWith(matrix.os, 'windows') && startsWith(matrix.ruby, 'jruby')
       run: gem install sassc -N
 
+  testExactBundlerVersion:
+    name: "Test with an exact Bundler version"
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: ./
+      with:
+        ruby-version: 2.6
+        bundler: 2.1.4
+    - run: bundle --version | grep -F 2.1.4
+
   lint:
     runs-on: ubuntu-20.04
     steps:

action.yml

@@ -11,7 +11,7 @@ inputs:
     default: 'default'
   bundler:
     description: |
-      The version of Bundler to install. Either 'none', 1, 2, 'latest' or 'Gemfile.lock'.
+      The version of Bundler to install. Either 'none', 'latest', 'Gemfile.lock', or a version number (e.g., 1, 2, 2.1.4).
       For 'Gemfile.lock', the version is determined based on the BUNDLED WITH section from the file Gemfile.lock, $BUNDLE_GEMFILE.lock or gems.locked.
       Defaults to 'Gemfile.lock' if the file exists and 'latest' otherwise.
     required: false

dist/index.js

@@ -51396,9 +51396,8 @@ function readBundledWithFromGemfileLock(lockFile) {
       const nextLine = lines[bundledWithLine+1]
       if (nextLine && /^\d+/.test(nextLine.trim())) {
         const bundlerVersion = nextLine.trim()
-        const majorVersion = bundlerVersion.match(/^\d+/)[0]
-        console.log(`Using Bundler ${majorVersion} from ${lockFile} BUNDLED WITH ${bundlerVersion}`)
-        return majorVersion
+        console.log(`Using Bundler ${bundlerVersion} from ${lockFile} BUNDLED WITH ${bundlerVersion}`)
+        return bundlerVersion
       }
     }
   }
@@ -51426,7 +51425,7 @@ async function installBundler(bundlerVersionInput, lockFile, platform, rubyPrefi
     throw new Error(`Cannot parse bundler input: ${bundlerVersion}`)
   }
 
-  if (engine === 'ruby' && rubyVersion.match(/^2\.[12]/)) {
+  if (engine === 'ruby' && rubyVersion.match(/^2\.[012]/)) {
     console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby <= 2.2')
     bundlerVersion = '1'
   } else if (engine === 'ruby' && rubyVersion.startsWith('2.3')) {
@@ -51437,9 +51436,9 @@ async function installBundler(bundlerVersionInput, lockFile, platform, rubyPrefi
     bundlerVersion = '1'
   }
 
-  if (common.isHeadVersion(rubyVersion) && common.isBundler2Default(engine, rubyVersion) && bundlerVersion === '2') {
+  if (common.isHeadVersion(rubyVersion) && common.isBundler2Default(engine, rubyVersion) && bundlerVersion.startsWith('2')) {
     console.log(`Using Bundler 2 shipped with ${engine}-${rubyVersion}`)
-  } else if (engine === 'truffleruby' && !common.isHeadVersion(rubyVersion) && bundlerVersion === '1') {
+  } else if (engine === 'truffleruby' && !common.isHeadVersion(rubyVersion) && bundlerVersion.startsWith('1')) {
     console.log(`Using Bundler 1 shipped with ${engine}`)
   } else {
     const gem = path.join(rubyPrefix, 'bin', 'gem')

index.js

@@ -181,9 +181,8 @@ function readBundledWithFromGemfileLock(lockFile) {
       const nextLine = lines[bundledWithLine+1]
       if (nextLine && /^\d+/.test(nextLine.trim())) {
         const bundlerVersion = nextLine.trim()
-        const majorVersion = bundlerVersion.match(/^\d+/)[0]
-        console.log(`Using Bundler ${majorVersion} from ${lockFile} BUNDLED WITH ${bundlerVersion}`)
-        return majorVersion
+        console.log(`Using Bundler ${bundlerVersion} from ${lockFile} BUNDLED WITH ${bundlerVersion}`)
+        return bundlerVersion
       }
     }
   }
@@ -211,7 +210,7 @@ async function installBundler(bundlerVersionInput, lockFile, platform, rubyPrefi
     throw new Error(`Cannot parse bundler input: ${bundlerVersion}`)
   }
 
-  if (engine === 'ruby' && rubyVersion.match(/^2\.[12]/)) {
+  if (engine === 'ruby' && rubyVersion.match(/^2\.[012]/)) {
     console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby <= 2.2')
     bundlerVersion = '1'
   } else if (engine === 'ruby' && rubyVersion.startsWith('2.3')) {
@@ -222,9 +221,9 @@ async function installBundler(bundlerVersionInput, lockFile, platform, rubyPrefi
     bundlerVersion = '1'
   }
 
-  if (common.isHeadVersion(rubyVersion) && common.isBundler2Default(engine, rubyVersion) && bundlerVersion === '2') {
+  if (common.isHeadVersion(rubyVersion) && common.isBundler2Default(engine, rubyVersion) && bundlerVersion.startsWith('2')) {
     console.log(`Using Bundler 2 shipped with ${engine}-${rubyVersion}`)
-  } else if (engine === 'truffleruby' && !common.isHeadVersion(rubyVersion) && bundlerVersion === '1') {
+  } else if (engine === 'truffleruby' && !common.isHeadVersion(rubyVersion) && bundlerVersion.startsWith('1')) {
     console.log(`Using Bundler 1 shipped with ${engine}`)
   } else {
     const gem = path.join(rubyPrefix, 'bin', 'gem')