Exclude application Rake tasks from help

Prior to this commit, `RakeCommand::rake_tasks` (and thus
`RakeCommand::printing_commands`) excluded tasks defined in the
application's `Rakefile`, but tasks defined in `lib/tasks/*.rake` were
still included.

This commit modifies `rake_tasks` to exclude any task defined solely by
the application.  And, as a result, the tasks can now be loaded via
`Rake::Application#load_rakefile`, which matches `RakeCommand::perform`.

Author: jonathanhefner

railties/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   `bin/rails --help` will now list only framework and plugin commands. Rake
+    tasks defined in `lib/tasks/*.rake` files will no longer be included. For a
+    list of those tasks, use `rake -T`.
+
+    *Jonathan Hefner*
+
 *   Allow calling `bin/rails restart` outside of app directory.
 
     The following would previously fail with a "No Rakefile found" error.

railties/lib/rails/commands/rake/rake_command.rb

@@ -22,25 +22,27 @@ def perform(task, args, config)
               raise UnrecognizedCommandError.new(unrecognized_task)
             end
 
-            if Rails.respond_to?(:root)
-              rake.options.suppress_backtrace_pattern = /\A(?!#{Regexp.quote(Rails.root.to_s)})/
-            end
+            rake.options.suppress_backtrace_pattern = non_app_file_pattern
             rake.standard_exception_handling { rake.top_level }
           end
         end
 
         private
+          def non_app_file_pattern
+            /\A(?!#{Regexp.quote Rails::Command.root.to_s})/
+          end
+
           def rake_tasks
             require_rake
 
             return @rake_tasks if defined?(@rake_tasks)
 
-            require_application!
-
             Rake::TaskManager.record_task_metadata = true
             Rake.application.instance_variable_set(:@name, "rails")
-            load_tasks
-            @rake_tasks = Rake.application.tasks.select(&:comment)
+            Rake.application.load_rakefile
+            @rake_tasks = Rake.application.tasks.select do |task|
+              task.comment && task.locations.any?(non_app_file_pattern)
+            end
           end
 
           def formatted_rake_tasks

railties/test/command/help_integration_test.rb

@@ -20,4 +20,18 @@ class Rails::Command::HelpIntegrationTest < ActiveSupport::TestCase
 
     assert_equal help, output
   end
+
+  test "excludes application Rake tasks from command listing" do
+    app_file "Rakefile", <<~RUBY, "a"
+      desc "my_task"
+      task :my_task_1
+    RUBY
+
+    app_file "lib/tasks/my_task.rake", <<~RUBY
+      desc "my_task"
+      task :my_task_2
+    RUBY
+
+    assert_no_match "my_task", rails("--help")
+  end
 end