The formatter loads from the same copy of the gem as the rest

lib/super_slim.rb

@@ -8,8 +8,10 @@
 require_relative "super_slim/runtime"
 
 module SuperSlim
-  autoload :Formatter, "super_slim/formatter"
-  autoload :RuboCop, "super_slim/rubocop"
+  # By their full path: a bare "super_slim/formatter" is the first one on the load path, which is another copy of the
+  # gem when this one was loaded by its path, as `exe/super-slim` does in a checkout.
+  autoload :Formatter, File.join(__dir__, "super_slim/formatter")
+  autoload :RuboCop, File.join(__dir__, "super_slim/rubocop")
 
   class Error < StandardError; end
   class InvalidAttributeNameError < Error; end

test/cli_test.rb

@@ -3,6 +3,7 @@
 require "minitest/autorun"
 require "stringio"
 require "fileutils"
+require "open3"
 require "tmpdir"
 require "super_slim/cli"
 
@@ -164,6 +165,20 @@ def test_control_characters_are_escaped_in_what_lint_prints
     end
   end
 
+  # `exe/super-slim` loads the checkout it sits in by path: with the gem installed too, a formatter looked up on
+  # the load path would be the installed one.
+  def test_the_formatter_comes_from_the_copy_of_the_gem_that_was_loaded
+    Dir.mktmpdir do |directory|
+      FileUtils.mkdir_p(File.join(directory, "super_slim"))
+      File.write(File.join(directory, "super_slim/formatter.rb"), "raise 'the formatter of another copy of the gem'\n")
+      script = "require #{File.expand_path("../lib/super_slim", __dir__).dump}; print SuperSlim::Formatter.call(%(p\\n   | Hello\\n))"
+      output, status = Open3.capture2e(RbConfig.ruby, "-I", directory, "-e", script)
+
+      assert_predicate status, :success?, output
+      assert_equal "p\n  | Hello\n", output
+    end
+  end
+
   private
 
   def template_name(number) = format("template_%03d.html.slim", number)