Improve the README, move the working directory section, mention $BUNDLE_GEMFILE

README.md

@@ -108,11 +108,16 @@ and the [condition and expression syntax](https://help.github.com/en/actions/ref
 * `.tool-versions` reads from the project's `.tool-versions` file
 * If the `ruby-version` input is not specified, `.ruby-version` is tried first, followed by `.tool-versions`
 
+### Working Directory
+
+The `working-directory` input can be set to resolve `.ruby-version`, `.tool-versions` and `Gemfile.lock`
+if they are not at the root of the repository, see [action.yml](action.yml) for details.
+
 ### Bundler
 
-By default, if there is a `Gemfile.lock` file with a `BUNDLED WITH` section,
+By default, if there is a `Gemfile.lock` file (or `$BUNDLE_GEMFILE.lock` if `$BUNDLE_GEMFILE` is set) 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 and 2.3 where only Bundler 1 is supported).
+Otherwise, the latest compatible Bundler version is installed (Bundler 2 on Ruby >= 2.4, Bundler 1 on Ruby < 2.4).
 
 This behavior can be customized, see [action.yml](action.yml) for details about the `bundler` input.
 
@@ -126,7 +131,7 @@ This action provides a way to automatically run `bundle install` and cache the r
 ```
 
 This caching speeds up installing gems significantly and avoids too many requests to RubyGems.org.  
-It needs a `Gemfile` under the [`working-directory`](#working-directory).  
+It needs a `Gemfile` (or `$BUNDLE_GEMFILE`) under the [`working-directory`](#working-directory).  
 The caching works whether there is a `Gemfile.lock` or not.
 If there is a `Gemfile.lock`, `bundle config --local deployment true` is used.
 
@@ -159,15 +164,9 @@ When using `.ruby-version`, replace `${{ matrix.ruby }}` with `${{ hashFiles('.r
 When using `.tool-versions`, replace `${{ matrix.ruby }}` with `${{ hashFiles('.tool-versions') }}`.
 
 This uses the [cache action](https://github.com/actions/cache).
-The code above is a more complete version of the [Ruby - Bundler example](https://github.com/actions/cache/blob/master/examples.md#ruby---\
-bundler).
+The code above is a more complete version of the [Ruby - Bundler example](https://github.com/actions/cache/blob/master/examples.md#ruby---bundler).
 Make sure to include `use-ruby` in the `key` to avoid conflicting with previous caches.
 
-### Working Directory
-
-The `working-directory` input can be set to resolve `.ruby-version`, `.tool-versions` and `Gemfile.lock`
-if they are not at the root of the repository, see [action.yml](action.yml) for details.
-
 ## Windows
 
 Note that running CI on Windows can be quite challenging if you are not very familiar with Windows.
@@ -192,9 +191,7 @@ Make sure to always use the latest release before reporting an issue on GitHub.
 This action follows semantic versioning with a moving `v1` branch.
 This follows the [recommendations](https://github.com/actions/toolkit/blob/master/docs/action-versioning.md) of GitHub Actions.
 
-## Limitations
-
-### Using self-hosted runners
+## Using self-hosted runners
 You must meet the following parameters to use this action with self-hosted runners:
 
 * Make sure that the operating system has `libyaml-0` installed

action.yml

@@ -10,7 +10,10 @@ inputs:
     required: false
     default: 'default'
   bundler:
-    description: 'The version of Bundler to install. Either none, 1, 2, latest or Gemfile.lock. The default tries Gemfile.lock and otherwise uses latest.'
+    description: |
+      The version of Bundler to install. Either 'none', 1, 2, 'latest' or 'Gemfile.lock'.
+      For 'Gemfile.lock', the version is determined based on the BUNDLED WITH section from the file ($BUNDLE_GEMFILE || Gemfile).lock.
+      Defaults to 'Gemfile.lock' if it exists and 'latest' otherwise.
     required: false
     default: 'default'
   bundler-cache:

dist/index.js

@@ -2339,9 +2339,9 @@ function setupPath(newPathEntries) {
   core.exportVariable('PATH', [...newPathEntries, ...cleanPath].join(path.delimiter))
 }
 
-function readBundledWithFromGemfileLock() {
-  if (fs.existsSync('Gemfile.lock')) {
-    const contents = fs.readFileSync('Gemfile.lock', 'utf8')
+function readBundledWithFromGemfileLock(path) {
+  if (fs.existsSync(path)) {
+    const contents = fs.readFileSync(path, 'utf8')
     const lines = contents.split(/\r?\n/)
     const bundledWithLine = lines.findIndex(line => /^BUNDLED WITH$/.test(line.trim()))
     if (bundledWithLine !== -1) {
@@ -2349,7 +2349,7 @@ function readBundledWithFromGemfileLock() {
       if (nextLine && /^\d+/.test(nextLine.trim())) {
         const bundlerVersion = nextLine.trim()
         const majorVersion = bundlerVersion.match(/^\d+/)[0]
-        console.log(`Using Bundler ${majorVersion} from Gemfile.lock BUNDLED WITH ${bundlerVersion}`)
+        console.log(`Using Bundler ${majorVersion} from ${path} BUNDLED WITH ${bundlerVersion}`)
         return majorVersion
       }
     }
@@ -2361,7 +2361,8 @@ async function installBundler(bundlerVersionInput, platform, rubyPrefix, engine,
   var bundlerVersion = bundlerVersionInput
 
   if (bundlerVersion === 'default' || bundlerVersion === 'Gemfile.lock') {
-    bundlerVersion = readBundledWithFromGemfileLock()
+    const gemfilePath = `${process.env['BUNDLE_GEMFILE'] || 'Gemfile'}.lock`
+    bundlerVersion = readBundledWithFromGemfileLock(gemfilePath)
     if (!bundlerVersion) {
       bundlerVersion = 'latest'
     }

index.js

@@ -153,9 +153,9 @@ function setupPath(newPathEntries) {
   core.exportVariable('PATH', [...newPathEntries, ...cleanPath].join(path.delimiter))
 }
 
-function readBundledWithFromGemfileLock() {
-  if (fs.existsSync('Gemfile.lock')) {
-    const contents = fs.readFileSync('Gemfile.lock', 'utf8')
+function readBundledWithFromGemfileLock(path) {
+  if (fs.existsSync(path)) {
+    const contents = fs.readFileSync(path, 'utf8')
     const lines = contents.split(/\r?\n/)
     const bundledWithLine = lines.findIndex(line => /^BUNDLED WITH$/.test(line.trim()))
     if (bundledWithLine !== -1) {
@@ -163,7 +163,7 @@ function readBundledWithFromGemfileLock() {
       if (nextLine && /^\d+/.test(nextLine.trim())) {
         const bundlerVersion = nextLine.trim()
         const majorVersion = bundlerVersion.match(/^\d+/)[0]
-        console.log(`Using Bundler ${majorVersion} from Gemfile.lock BUNDLED WITH ${bundlerVersion}`)
+        console.log(`Using Bundler ${majorVersion} from ${path} BUNDLED WITH ${bundlerVersion}`)
         return majorVersion
       }
     }
@@ -175,7 +175,8 @@ async function installBundler(bundlerVersionInput, platform, rubyPrefix, engine,
   var bundlerVersion = bundlerVersionInput
 
   if (bundlerVersion === 'default' || bundlerVersion === 'Gemfile.lock') {
-    bundlerVersion = readBundledWithFromGemfileLock()
+    const gemfilePath = `${process.env['BUNDLE_GEMFILE'] || 'Gemfile'}.lock`
+    bundlerVersion = readBundledWithFromGemfileLock(gemfilePath)
     if (!bundlerVersion) {
       bundlerVersion = 'latest'
     }