Install specific bundler version when minor and patch versions are given (#139)

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,19 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+<!--
+Before filing this issue:
+* If the issue happens on JRuby or TruffleRuby, and does not happen on CRuby (please check), file an issue there instead. It's very unlikely ruby/setup-ruby is the cause.
+* Try to reproduce the issue locally by following the workflow steps (including all all commands done by ruby/setup-ruby, except for `Downloading Ruby` & `Extracting Ruby`). If it does reproduce locally, it's not a ruby/setup-ruby issue.
+
+Please provide:
+* the code of or a link to the workflow used
+* the link to the log of a failed workflow job
+* the command and output of the step failing
+-->

README.md

@@ -57,7 +57,7 @@ for Ubuntu and macOS and in [windows-versions.js](windows-versions.js) for Windo
 
 ```yaml
 name: My workflow
-on: [push]
+on: [push, pull_request]
 jobs:
   test:
     runs-on: ubuntu-latest
@@ -76,7 +76,7 @@ This matrix tests all stable releases and `head` versions of MRI, JRuby and Truf
 
 ```yaml
 name: My workflow
-on: [push]
+on: [push, pull_request]
 jobs:
   test:
     strategy:
@@ -98,7 +98,7 @@ jobs:
 
 ```yaml
 name: My workflow
-on: [push]
+on: [push, pull_request]
 jobs:
   test:
     strategy:
@@ -162,9 +162,19 @@ If there is a `Gemfile.lock` (or `$BUNDLE_GEMFILE.lock` or `gems.locked`), `bund
 To use a `Gemfile` which is not at the root or has a different name, set `BUNDLE_GEMFILE` in the `env` at the job level
 as shown in the [example](#matrix-of-gemfiles).
 
+When there is no lockfile, one is generated with `bundle lock`, which is the same as `bundle install` would do first before actually fetching any gem.
+In other words, it works exactly like `bundle install`.
+The hash of the generated lockfile is then used for caching, which is the only correct approach.
+
 To perform caching, this action will use `bundle config --local path $PWD/vendor/bundle`.  
 Therefore, the Bundler `path` should not be changed in your workflow for the cache to work (no `bundle config path`).
 
+#### Caching `bundle install` manually
+
+It is also possible to cache gems manually, but this is not recommended because it is verbose and *very difficult* to do correctly.
+There are many concerns which means using `actions/cache` is never enough for caching gems (e.g., incomplete cache key, cleaning old gems when restoring from another key, correctly hashing the lockfile if not checked in, OS versions, ABI compatibility for `ruby-head`, etc).
+So, please use `bundler-cache: true` instead and report any issue.
+
 ## Windows
 
 Note that running CI on Windows can be quite challenging if you are not very familiar with Windows.

dist/index.js

@@ -52058,7 +52058,8 @@ async function installBundler(bundlerVersionInput, lockFile, platform, rubyPrefi
     console.log(`Using Bundler 1 shipped with ${engine}`)
   } else {
     const gem = path.join(rubyPrefix, 'bin', 'gem')
-    await exec.exec(gem, ['install', 'bundler', '-v', `~> ${bundlerVersion}`, '--no-document'])
+    const bundlerVersionConstraint = bundlerVersion.match(/^\d+\.\d+\.\d+/) ? bundlerVersion : `~> ${bundlerVersion}`
+    await exec.exec(gem, ['install', 'bundler', '-v', bundlerVersionConstraint, '--no-document'])
   }
 
   return bundlerVersion

index.js

@@ -229,7 +229,8 @@ async function installBundler(bundlerVersionInput, lockFile, platform, rubyPrefi
     console.log(`Using Bundler 1 shipped with ${engine}`)
   } else {
     const gem = path.join(rubyPrefix, 'bin', 'gem')
-    await exec.exec(gem, ['install', 'bundler', '-v', `~> ${bundlerVersion}`, '--no-document'])
+    const bundlerVersionConstraint = bundlerVersion.match(/^\d+\.\d+\.\d+/) ? bundlerVersion : `~> ${bundlerVersion}`
+    await exec.exec(gem, ['install', 'bundler', '-v', bundlerVersionConstraint, '--no-document'])
   }
 
   return bundlerVersion