Merge pull request #49525 from abhaynikam/fix-app-generated-dockerfile-to-use-correct-ruby-version

Ensures the Rails generated Dockerfile uses correct ruby version and matches Gemfile

Author: byroot

railties/lib/rails/generators/rails/app/templates/Dockerfile.tt

@@ -1,7 +1,7 @@
 # syntax = docker/dockerfile:1
 
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
-ARG RUBY_VERSION=<%= Gem.ruby_version %>
+ARG RUBY_VERSION=<%= gem_ruby_version %>
 FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim as base
 
 # Rails app lives here

railties/test/generators/app_generator_test.rb

@@ -955,6 +955,9 @@ def test_inclusion_of_ruby_version
     assert_file "Gemfile" do |content|
       assert_match(/ruby "#{Gem::Version.new(Gem::VERSION) >= Gem::Version.new("3.3.13") ? Gem.ruby_version : RUBY_VERSION}"/, content)
     end
+    assert_file "Dockerfile" do |content|
+      assert_match(/ARG RUBY_VERSION=#{Gem::Version.new(Gem::VERSION) >= Gem::Version.new("3.3.13") ? Gem.ruby_version : RUBY_VERSION}/, content)
+    end
     assert_file ".ruby-version" do |content|
       if ENV["RBENV_VERSION"]
         assert_match(/#{ENV["RBENV_VERSION"]}/, content)