Stop injecting rails_12factor from the Heroku generator

CHANGELOG.md

@@ -1,3 +1,11 @@
+main
+------
+
+* Stop adding `rails_12factor` to the `Gemfile` from `rails generate
+  ember:heroku`. Rails serves the twelve-factor behaviour the gem backported
+  natively since `5.0`, and every Rails version this gem supports is `>= 5.2`.
+  To upgrade, remove `rails_12factor` from your project's `Gemfile`
+
 0.13.2
 ------
 

lib/generators/ember/heroku/USAGE

@@ -11,8 +11,5 @@ Description:
 Example:
     rails generate ember:heroku
 
-    This will install the following gems:
-        rails_12factor
-
     This will create:
         package.json

lib/generators/ember/heroku/heroku_generator.rb

@@ -14,10 +14,6 @@ def identify_as_yarn_project
       end
     end
 
-    def inject_12factor_gem
-      gem "rails_12factor", group: [:staging, :production]
-    end
-
     private
 
     def cache_directories

spec/generators/ember/heroku/heroku_generator_spec.rb

@@ -31,6 +31,21 @@
     end
   end
 
+  describe "Gemfile" do
+    it "leaves the Gemfile untouched" do
+      setup_destination
+      configure_application
+
+      run_generator
+
+      expect(gemfile_contents).to eq("")
+    end
+
+    def gemfile_contents
+      destination_root.join("Gemfile").read
+    end
+  end
+
   describe "package.json" do
     it "includes the root directory node_modules" do
       setup_destination
@@ -113,10 +128,10 @@ def configure_application(**options)
   def setup_destination
     prepare_destination
 
-    create_empty_gemfile_for_bundler
+    create_empty_gemfile
   end
 
-  def create_empty_gemfile_for_bundler
+  def create_empty_gemfile
     FileUtils.touch(destination_root.join("Gemfile"))
   end
 end