Export BUNDLER_VERSION after installing Bundler

* Fixes #440

bundler.js

@@ -126,7 +126,7 @@ export async function installBundler(bundlerVersionInput, rubygemsInputSet, lock
  const targetRubyVersion = common.targetRubyVersion(engine, rubyVersion)
  // Use Bundler 2.3 when we use Ruby 2.3.2 - 2.5
  // Use Bundler 2.4 when we use Ruby 2.6-2.7
- if (bundlerVersion == '2') {
+ if (bundlerVersion === '2') {
  if (targetRubyVersion <= 2.5) { // < 2.3.2 already handled above
  console.log('Ruby 2.3.2 - 2.5 only works with Bundler 2.3')
  bundlerVersion = '2.3'
@@ -146,6 +146,14 @@ export async function installBundler(bundlerVersionInput, rubygemsInputSet, lock
 
  await exec.exec(gem, ['install', 'bundler', ...force, '-v', bundlerVersionConstraint])
 
+ if (bundlerVersion.startsWith('1') && common.isBundler2Default(engine, rubyVersion)) {
+ // If Bundler 1 is specified on Rubies which ship with Bundler 2,
+ // we need to specify which Bundler version to use explicitly until the lockfile exists.
+ // We actually set it globally for the case of bundler-cache: false with manual bundler install later.
+ console.log(`Setting BUNDLER_VERSION=${bundlerVersion} to ensure Bundler 1 is used`)
+ core.exportVariable('BUNDLER_VERSION', bundlerVersion)
+ }
+
  return bundlerVersion
 }
 
@@ -155,27 +163,19 @@ export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVer
  return false
  }
 
- let envOptions = {}
- if (bundlerVersion.startsWith('1') && common.isBundler2Default(engine, rubyVersion)) {
- // If Bundler 1 is specified on Rubies which ship with Bundler 2,
- // we need to specify which Bundler version to use explicitly until the lockfile exists.
- console.log(`Setting BUNDLER_VERSION=${bundlerVersion} for "bundle config|lock" commands below to ensure Bundler 1 is used`)
- envOptions = { env: { ...process.env, BUNDLER_VERSION: bundlerVersion } }
- }
-
  // config
  const cachePath = 'vendor/bundle'
  // An absolute path, so it is reliably under $PWD/vendor/bundle, and not relative to the gemfile's directory
  const bundleCachePath = path.join(process.cwd(), cachePath)
 
- await exec.exec('bundle', ['config', '--local', 'path', bundleCachePath], envOptions)
+ await exec.exec('bundle', ['config', '--local', 'path', bundleCachePath])
 
  if (fs.existsSync(lockFile)) {
- await exec.exec('bundle', ['config', '--local', 'deployment', 'true'], envOptions)
+ await exec.exec('bundle', ['config', '--local', 'deployment', 'true'])
  } else {
  // Generate the lockfile so we can use it to compute the cache key.
  // This will also automatically pick up the latest gem versions compatible with the Gemfile.
- await exec.exec('bundle', ['lock'], envOptions)
+ await exec.exec('bundle', ['lock'])
  }
 
  await afterLockFile(lockFile, platform, engine, rubyVersion)