Merge pull request rails#47472 from skipkayhil/fix-old-ruby-dockerfile-packages

Fix parsing ruby version for Dockerfile packages

Author: yahonda

railties/lib/rails/generators/app_base.rb

@@ -520,11 +520,11 @@ def dockerfile_build_packages
           # how python is installed with the bullseye release.  Below
           # is based on debian release included with the Ruby images on
           # Dockerhub.
-          case Gem.ruby_version
-          when /^2.7/
-            bullseye = ruby_version >= "2.7.4"
-          when /^3.0/
-            bullseye = ruby_version >= "3.0.2"
+          case Gem.ruby_version.to_s
+          when /^2\.7/
+            bullseye = Gem.ruby_version >= "2.7.4"
+          when /^3\.0/
+            bullseye = Gem.ruby_version >= "3.0.2"
           else
             bullseye = true
           end

railties/test/generators/app_generator_test.rb

@@ -1047,6 +1047,17 @@ def test_dockerfile
     end
   end
 
+  def test_old_rubies_do_not_use_bullseye_python
+    Gem.stub(:ruby_version, Gem::Version.new("2.7.0")) do
+      run_generator [destination_root, "--js=esbuild"]
+    end
+
+    assert_file "Dockerfile" do |content|
+      assert_match(/python/, content)
+      assert_no_match(/python-is-python3/, content)
+    end
+  end
+
   def test_skip_docker
     run_generator [destination_root, "--skip-docker"]