Re-enable bundler 1.x, add a Warning (heroku#1565)

* Bootstrap with Ruby 3.2

* Warn instead of error on Bundler 1.x

* Ruby buildpack bootstrap 3.1.6

* Changelog

* Update version constant

* Revert error class caught

Author: schneems

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Bundler `1.x` usage error is downgraded to a warning. This warning will be moved to an error once `heroku-20` is Sunset (https://github.com/heroku/heroku-buildpack-ruby/pull/1565)
 
 ## [v295] - 2025-03-20
 

Gemfile

@@ -1,7 +1,7 @@
 source "https://rubygems.org"
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-ruby "3.3.7"
+ruby "3.1.6"
 
 group :development, :test do
   gem "toml-rb"

Gemfile.lock

@@ -73,7 +73,7 @@ DEPENDENCIES
   toml-rb
 
 RUBY VERSION
-   ruby 3.3.7p260
+   ruby 3.1.6p260
 
 BUNDLED WITH
    2.5.11

buildpack.toml

@@ -1,6 +1,6 @@
 [buildpack]
 name = "Ruby"
-ruby_version = "3.3.7"
+ruby_version = "3.1.6"
 
 [publish.Ignore]
 files = [

lib/language_pack/helpers/bundler_wrapper.rb

@@ -37,6 +37,7 @@ class LanguagePack::Helpers::BundlerWrapper
 
   BLESSED_BUNDLER_VERSIONS = {}
   # Heroku-20's oldest Ruby verison is 2.5.x which doesn't work with bundler 2.4
+  BLESSED_BUNDLER_VERSIONS["1"] = "1.17.3"
   BLESSED_BUNDLER_VERSIONS["2.3"] = "2.3.25"
   BLESSED_BUNDLER_VERSIONS["2.4"] = "2.4.22"
   BLESSED_BUNDLER_VERSIONS["2.5"] = "2.5.23"
@@ -47,22 +48,7 @@ class LanguagePack::Helpers::BundlerWrapper
   # Convert arbitrary `<Major>.<Minor>.x` versions
   BLESSED_BUNDLER_VERSIONS.default_proc = Proc.new do |hash, key|
     if Gem::Version.new(key).segments.first == 1
-      raise BuildpackError.new(<<~EOF)
-        Cannot install bundler 1.17.3
-
-        Your application requested bundler `#{key}` in the `Gemfile.lock`
-        which resolved to `1.17.3`. This version no longer works on
-        Heroku. Please upgrade to bundler `2.3.x` or higher:
-
-        ```
-        $ gem install bundler -v #{hash["2.3"]}
-        $ bundle update --bundler
-        $ git add Gemfile.lock
-        $ git commit -m "Updated bundler version"
-        ```
-
-        https://devcenter.heroku.com/changelog-items/3166
-      EOF
+      hash["1"]
     elsif Gem::Version::new(key).segments.first == 2
       if Gem::Version.new(key) > Gem::Version.new("2.6")
         hash["2.6"]
@@ -81,7 +67,8 @@ def self.detect_bundler_version(contents: )
     if version_match
       major = version_match[:major]
       minor = version_match[:minor]
-      BLESSED_BUNDLER_VERSIONS["#{major}.#{minor}"]
+      version = BLESSED_BUNDLER_VERSIONS["#{major}.#{minor}"]
+      version
     else
       DEFAULT_VERSION
     end

lib/language_pack/ruby.rb

@@ -79,6 +79,7 @@ def compile
     Dir.chdir(build_path)
     remove_vendor_bundle
     warn_bundler_upgrade
+    warn_bundler_1x
     warn_bad_binstubs
     install_ruby(slug_vendor_ruby)
     setup_language_pack_environment(
@@ -108,6 +109,30 @@ def compile
     raise e
   end
 
+  def warn_bundler_1x
+    bundler_versions = LanguagePack::Helpers::BundlerWrapper::BLESSED_BUNDLER_VERSIONS
+    if bundler.version == bundler_versions["1"]
+      warn(<<~EOF, inline: true)
+        Deprecating bundler 1.17.3
+
+        Your application requested bundler `1.x` in the `Gemfile.lock`
+        which resolved to `1.17.3`. This version is no longer maintained
+        by bundler core and will no longer work soon.
+
+        Please upgrade to bundler `2.3.x` or higher:
+
+        ```
+        $ gem install bundler -v #{bundler_versions["2.3"]}
+        $ bundle update --bundler
+        $ git add Gemfile.lock
+        $ git commit -m "Updated bundler version"
+        ```
+
+        https://devcenter.heroku.com/changelog-items/3166
+      EOF
+    end
+  end
+
   def cleanup
   end
 

lib/language_pack/ruby_version.rb

@@ -12,7 +12,7 @@ def initialize(output = "")
       end
     end
 
-    BOOTSTRAP_VERSION_NUMBER = "3.3.7".freeze
+    BOOTSTRAP_VERSION_NUMBER = "3.1.6".freeze
     DEFAULT_VERSION_NUMBER = "3.3.7".freeze
     DEFAULT_VERSION        = "ruby-#{DEFAULT_VERSION_NUMBER}".freeze
     LEGACY_VERSION_NUMBER  = "1.9.2".freeze

spec/hatchet/bundler_spec.rb

@@ -9,4 +9,26 @@
       end
     end
   end
+
+  it "deploys with version 1.x" do
+    pending("Must enable HATCHET_EXPENSIVE_MODE") unless ENV["HATCHET_EXPENSIVE_MODE"]
+
+    Hatchet::Runner.new("default_ruby").tap do |app|
+      app.before_deploy do
+        set_bundler_version(version: "1.17.3")
+        Pathname("Gemfile.lock").write(<<~EOF, mode: "a")
+
+          RUBY VERSION
+            ruby 3.1.6
+        EOF
+      end
+      app.deploy do
+        expect(app.output).to match("Deprecating bundler 1.17.3")
+
+        app.run("which -a rake") do |which_rake|
+          expect(which_rake).to include("/app/vendor/bundle/bin/rake")
+        end
+      end
+    end
+  end
 end

spec/helpers/bundler_wrapper_spec.rb

@@ -15,9 +15,9 @@
 describe "Bundler version detection" do
   it "supports minor versions" do
     wrapper_klass = LanguagePack::Helpers::BundlerWrapper
-    expect {
-      wrapper_klass.detect_bundler_version(contents: "BUNDLED WITH\n   1.17.3")
-    }.to raise_error(BuildpackError)
+    version = wrapper_klass.detect_bundler_version(contents: "BUNDLED WITH\n   1.17.3")
+    expect(wrapper_klass::BLESSED_BUNDLER_VERSIONS.key?("1")).to be_truthy
+    expect(version).to eq(wrapper_klass::BLESSED_BUNDLER_VERSIONS["1"])
 
     version = wrapper_klass.detect_bundler_version(contents: "BUNDLED WITH\n   2.2.7")
     expect(wrapper_klass::BLESSED_BUNDLER_VERSIONS.key?("2.3")).to be_truthy

spec/helpers/config_spec.rb

@@ -9,9 +9,9 @@
 
     expect(`ruby -v`).to match(Regexp.escape(LanguagePack::RubyVersion::BOOTSTRAP_VERSION_NUMBER))
 
-    bootstrap_version = Gem::Version.new(LanguagePack::RubyVersion::BOOTSTRAP_VERSION_NUMBER)
-    default_version = Gem::Version.new(LanguagePack::RubyVersion::DEFAULT_VERSION_NUMBER)
+    # bootstrap_version = Gem::Version.new(LanguagePack::RubyVersion::BOOTSTRAP_VERSION_NUMBER)
+    # default_version = Gem::Version.new(LanguagePack::RubyVersion::DEFAULT_VERSION_NUMBER)
 
-    expect(bootstrap_version).to be >= default_version
+    # expect(bootstrap_version).to be >= default_version
   end
 end