Remove Heroku-20 support (heroku#1591)

* Remove heroku-20 version logic

* Update error message

* Remove unsupported Bundler versions

Ruby 3+ ships with a bundler version and Ruby 3.1 ships with Bundler 2.5:

```
$ /Users/rschneeman/.rubies/ruby-3.1.6/bin/bundle -v
Bundler version 2.5.11
```

I think we could also remove the 2.3 and 2.4 bundler versions from the hash, but would need to check observability to be sure. It's not hurting things for now.

* Update download presence logic to remove heroku-20

* Remove heroku-18 string from spec

* Update test to non EOL stack

* Remove (more) deprecated stack references

* Refactor: Move spec file

There's only one test in `installers/`, and it's easier to run all "helpers" at once this way.

* Remove Ruby 1.9 code

* Remove Ruby <2.1 code

* Remove Ruby <2.1 "syck hack" code

* Remove Ruby < 1.9 logic

* Remove Ruby 1.8.7 code and duplicate env var

* Remove older changelogs (keeping 2024-2025)

* Remove unused Ruby 2.6 code

* Remove unused constant

* Remove unused logging code

* Remove unused methods

* DRY up logic

* Remove hardcoded false in vendored_bundle?

Code was added in Ruby ~2.5 and never moved heroku@5dbc840

* All bundler versions supported provide multi platform support

* Remove newline

* Remove unused method

* Remove legacy cache clear code

* Fix code alignment

* Remove bundler < 2.1 configuration

* Remove bundler conditional

```
$ irb
irb(main):001> Gem::Version.new("2.3.1") > Gem::Version.new("2.3")
=> true
```

* Changelog

* Remove no-op libyaml

Added in heroku@eac7584 and removed some time later, we have libyaml on the system and this is a no-op. https://devcenter.heroku.com/articles/stack-packages

* Remove unused files and Rake code

* Remove purely `true` variable

* Update lib/language_pack/helpers/bundler_wrapper.rb

Co-authored-by: Colin Casey <casey.colin@gmail.com>
Signed-off-by: Richard Schneeman <richard.schneeman+no-recruiters@gmail.com>

* Assert no accidental cache purge message

heroku#1591 (comment)

---------

Signed-off-by: Richard Schneeman <richard.schneeman+no-recruiters@gmail.com>
Co-authored-by: Colin Casey <casey.colin@gmail.com>

Author: schneems

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Removed support for Ubuntu 20.04 (and thus Heroku-20 / `heroku/builder:20`). This includes removing support for Ruby < 3.1 and Bundler < 2.3. (https://github.com/heroku/buildpacks-ruby/pull/1591)
 
 ## [v307] - 2025-05-14
 

Rakefile

@@ -6,64 +6,8 @@
 require "fileutils"
 require "tmpdir"
 require 'hatchet/tasks'
-ENV["BUILDPACK_LOG_FILE"] ||= "tmp/buildpack.log"
-
 require_relative 'lib/rake/deploy_check'
 
-S3_BUCKET_REGION = "us-east-1"
-S3_BUCKET_NAME  = "heroku-buildpack-ruby"
-
-def s3_tools_dir
-  File.expand_path("../support/s3", __FILE__)
-end
-
-def s3_upload(tmpdir, name)
-  sh("#{s3_tools_dir}/s3 put #{S3_BUCKET_NAME} #{name}.tgz #{tmpdir}/#{name}.tgz")
-end
-
-def vendor_plugin(git_url, branch = nil)
-  name = File.basename(git_url, File.extname(git_url))
-  Dir.mktmpdir("#{name}-") do |tmpdir|
-    FileUtils.rm_rf("#{tmpdir}/*")
-
-    Dir.chdir(tmpdir) do
-      sh "git clone #{git_url} ."
-      sh "git checkout origin/#{branch}" if branch
-      FileUtils.rm_rf("#{name}/.git")
-      sh("tar czvf #{tmpdir}/#{name}.tgz *")
-      s3_upload(tmpdir, name)
-    end
-  end
-end
-
-def in_gem_env(gem_home, &block)
-  old_gem_home = ENV['GEM_HOME']
-  old_gem_path = ENV['GEM_PATH']
-  ENV['GEM_HOME'] = ENV['GEM_PATH'] = gem_home.to_s
-
-  yield
-
-  ENV['GEM_HOME'] = old_gem_home
-  ENV['GEM_PATH'] = old_gem_path
-end
-
-def install_gem(gem_name, version)
-  name = "#{gem_name}-#{version}"
-  Dir.mktmpdir("#{gem_name}-#{version}") do |tmpdir|
-    Dir.chdir(tmpdir) do |dir|
-      FileUtils.rm_rf("#{tmpdir}/*")
-
-      in_gem_env(tmpdir) do
-        sh("unset RUBYOPT; gem install #{gem_name} --version #{version} --no-ri --no-rdoc --env-shebang")
-        sh("rm #{gem_name}-#{version}.gem")
-        sh("rm -rf cache/#{gem_name}-#{version}.gem")
-        sh("tar czvf #{tmpdir}/#{name}.tgz *")
-        s3_upload(tmpdir, name)
-      end
-    end
-  end
-end
-
 namespace :buildpack do
   desc "prepares the next version of the buildpack for release"
   task :prepare do
@@ -91,21 +35,6 @@ namespace :buildpack do
   end
 end
 
-desc "update plugins"
-task "plugins:update" do
-  vendor_plugin "https://github.com/heroku/rails_log_stdout.git", "legacy"
-  vendor_plugin "https://github.com/pedro/rails3_serve_static_assets.git"
-  vendor_plugin "https://github.com/hone/rails31_enable_runtime_asset_compilation.git"
-end
-
-desc "install vendored gem"
-task "gem:install", :gem, :version do |t, args|
-  gem     = args[:gem]
-  version = args[:version]
-
-  install_gem(gem, version)
-end
-
 begin
   require 'rspec/core/rake_task'
 

bin/support/ruby_compile

@@ -22,9 +22,7 @@ begin
   LanguagePack::ShellHelpers.initialize_env(ARGV[2])
   if pack = LanguagePack.detect(ARGV[0], ARGV[1])
     pack.topic("Compiling #{pack.name}")
-    pack.log("compile") do
-      pack.compile
-    end
+    pack.compile
   end
 rescue Exception => e
   LanguagePack::ShellHelpers.display_error_and_exit(e)

bin/support/ruby_test-compile

@@ -22,9 +22,7 @@ begin
   if pack = LanguagePack.detect(ARGV[0], ARGV[1])
     LanguagePack::ShellHelpers.initialize_env(ARGV[2])
     pack.topic("Setting up Test for #{pack.name}")
-    pack.log("test_compile") do
-      pack.compile
-    end
+    pack.compile
   end
 rescue Exception => e
   LanguagePack::ShellHelpers.display_error_and_exit(e)