Load Rake tasks only once for command suggestions

Follow-up to rails#47208.

`UnrecognizedCommandError` calls `printing_commands` to make "Did you
mean?" suggestions.  `printing_commands` calls `RakeCommand::rake_tasks`,
which loads the Rake tasks if they have not been memoized.  If the tasks
have already been loaded by `RakeCommand::perform` (but not memoized by
`RakeCommand::rake_tasks`), then the tasks will be loaded a second time.
This can cause, for example, constant redefinition warnings if the task
files define constants.

Therefore, this commit memoizes the tasks from `RakeCommand::perform`
before raising `UnrecognizedCommandError`.

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

@@ -19,6 +19,7 @@ def printing_commands
         def perform(task, args, config)
           with_rake(task, *args) do |rake|
             if unrecognized_task = rake.top_level_tasks.find { |task| !rake.lookup(task[/[^\[]+/]) }
+              @rake_tasks = rake.tasks
               raise UnrecognizedCommandError.new(unrecognized_task)
             end
 

railties/test/command/help_integration_test.rb

@@ -14,6 +14,18 @@ class Rails::Command::HelpIntegrationTest < ActiveSupport::TestCase
     assert_match "Did you mean?  version", output
   end
 
+  test "loads Rake tasks only once on unrecognized command" do
+    app_file "lib/tasks/my_task.rake", <<~RUBY
+      puts "MY_TASK already defined? => \#{!!defined?(MY_TASK)}"
+      MY_TASK = true
+    RUBY
+
+    output = rails "vershen", allow_failure: true
+
+    assert_match "MY_TASK already defined? => false", output
+    assert_no_match "MY_TASK already defined? => true", output
+  end
+
   test "prints help via `X:help` command when running `X` and `X:X` command is not defined" do
     help = rails "dev:help"
     output = rails "dev", allow_failure: true