Rewrite using pattern matching

mattbrictson · Feb 18, 2024 · 08c1fac · 08c1fac
1 parent 64ebbc1
commit 08c1fac
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Showing 2 changed files with 53 additions and 67 deletions.
diff --git a/lib/mighty_test/watcher.rb b/lib/mighty_test/watcher.rb
@@ -5,71 +5,64 @@ class Watcher
     WATCHING_FOR_CHANGES = "Watching for changes to source and test files. Press ctrl-c to exit.".freeze
 
     def initialize(extra_args: [], file_system: FileSystem.new, system_proc: method(:system))
-      @dispatcher = Concurrent::MVar.new
+      @event = Concurrent::MVar.new
       @extra_args = extra_args
       @file_system = file_system
       @system_proc = system_proc
     end
 
-    def run
+    def run(iterations: :indefinitely)
       start_listener
       puts WATCHING_FOR_CHANGES
-      process_dispatched_events
+
+      loop = iterations == :indefinitely ? method(:loop) : iterations.method(:times)
+      loop.call do
+        case await_next_event
+        in [:file_system_changed, paths]
+          mt(*paths) if paths.any?
+        in [:tests_completed, :pass | :fail]
+          puts WATCHING_FOR_CHANGES
+        end
+      end
     ensure
       listener&.stop
     end
 
-    # Normally `run` proceeds indefinitely until the user interrupts with ctrl-c.
-    # This is a way to stop it gracefully in unit tests.
-    def interrupt
-      dispatch { :stop }
-    end
-
     private
 
     attr_reader :extra_args, :file_system, :listener, :system_proc
 
-    def file_system_changed(modified, added, _removed)
-      test_paths = [*modified, *added].filter_map do |path|
-        file_system.find_matching_test_file(path)
-      end
-      return if test_paths.empty?
-
-      run_tests(*test_paths.uniq)
-    end
-
-    def run_tests(*test_paths)
-      begin
-        system_proc.call("mt", *extra_args, "--", *test_paths.flatten)
-      rescue Interrupt
-        # Pressing ctrl-c kills the fs_event background process, so we have to manually restart it.
-        restart_listener
-      end
-      puts WATCHING_FOR_CHANGES
+    def mt(*test_paths)
+      success = system_proc.call("mt", *extra_args, "--", *test_paths.flatten)
+      post_event(:tests_completed, success ? :pass : :fail)
+    rescue Interrupt
+      # Pressing ctrl-c kills the fs_event background process, so we have to manually restart it.
+      restart_listener
     end
 
     def start_listener
       listener.stop if listener && !listener.stopped?
-      @listener = file_system.listen do |*args|
-        listener.pause
-        dispatch do
-          file_system_changed(*args)
-          listener.start if listener.paused?
+
+      @listener = file_system.listen do |modified, added, _removed|
+        # Pause listener so that subsequent changes are queued up while we are running the tests
+        listener.pause unless listener.stopped?
+
+        test_paths = [*modified, *added].filter_map do |path|
+          file_system.find_matching_test_file(path)
         end
+
+        post_event(:file_system_changed, test_paths.uniq)
       end
     end
     alias restart_listener start_listener
 
-    def dispatch(&block)
-      @dispatcher.put(block)
-      true
+    def await_next_event
+      listener.start if listener.paused?
+      @event.take
     end
 
-    def process_dispatched_events
-      loop do
-        result = @dispatcher.take.call
-        break if result == :stop
-      end
+    def post_event(*event)
+      @event.put(event)
     end
   end
 end
diff --git a/test/mighty_test/watcher_test.rb b/test/mighty_test/watcher_test.rb
@@ -8,22 +8,31 @@ def test_watcher_passes_unique_set_of_test_files_to_mt_command_based_on_changes_
       system_proc { |*args| puts "[SYSTEM] #{args.join(' ')}" }
       listen_thread do |callback|
         callback.call(["lib/example.rb", "test/focused_test.rb"], ["test/focused_test.rb"], [])
-        @watcher.interrupt
       end
 
-      stdout, = run_watcher(in: fixtures_path.join("example_project"))
+      stdout, = run_watcher(iterations: 1, in: fixtures_path.join("example_project"))
 
       assert_includes(stdout, "[SYSTEM] mt -- test/example_test.rb test/focused_test.rb\n")
     end
 
+    def test_watcher_does_nothing_if_a_detected_change_has_no_corresponding_test_file
+      system_proc { |*args| puts "[SYSTEM] #{args.join(' ')}" }
+      listen_thread do |callback|
+        callback.call(["lib/example/version.rb"], [], [])
+      end
+
+      stdout, = run_watcher(iterations: 1, in: fixtures_path.join("example_project"))
+
+      refute_includes(stdout, "[SYSTEM]")
+    end
+
     def test_watcher_passes_extra_args_through_to_mt_command
       system_proc { |*args| puts "[SYSTEM] #{args.join(' ')}" }
       listen_thread do |callback|
         callback.call(["test/example_test.rb"], [], [])
-        @watcher.interrupt
       end
 
-      stdout, = run_watcher(extra_args: ["--fail-fast"], in: fixtures_path.join("example_project"))
+      stdout, = run_watcher(iterations: 1, extra_args: ["--fail-fast"], in: fixtures_path.join("example_project"))
 
       assert_includes(stdout, "[SYSTEM] mt --fail-fast -- test/example_test.rb\n")
     end
@@ -35,10 +44,9 @@ def test_watcher_prints_a_status_message_after_successful_test_run
       end
       listen_thread do |callback|
         callback.call(["test/example_test.rb"], [], [])
-        @watcher.interrupt
       end
 
-      stdout, = run_watcher(in: fixtures_path.join("example_project"))
+      stdout, = run_watcher(iterations: 2, in: fixtures_path.join("example_project"))
 
       assert_includes(stdout, <<~EXPECTED)
         [SYSTEM] mt -- test/example_test.rb
@@ -53,46 +61,31 @@ def test_watcher_prints_a_status_message_after_failed_test_run
       end
       listen_thread do |callback|
         callback.call(["test/example_test.rb"], [], [])
-        @watcher.interrupt
       end
 
-      stdout, = run_watcher(in: fixtures_path.join("example_project"))
+      stdout, = run_watcher(iterations: 2, in: fixtures_path.join("example_project"))
 
       assert_includes(stdout, <<~EXPECTED)
         [SYSTEM] mt -- test/example_test.rb
         Watching for changes to source and test files. Press ctrl-c to exit.
       EXPECTED
     end
 
-    def test_watcher_does_nothing_if_a_detected_change_has_no_corresponding_test_file
-      system_proc { |*args| puts "[SYSTEM] #{args.join(' ')}" }
-      listen_thread do |callback|
-        callback.call(["lib/example/version.rb"], [], [])
-        @watcher.interrupt
-      end
-
-      stdout, = run_watcher(in: fixtures_path.join("example_project"))
-
-      refute_includes(stdout, "[SYSTEM]")
-    end
-
     def test_watcher_restarts_the_listener_when_a_test_run_is_interrupted
       thread_count = 0
       system_proc { |*| raise Interrupt }
       listen_thread do |callback|
         thread_count += 1
-        callback.call(["test/example_test.rb"], [], [])
-        @watcher.interrupt if thread_count > 1
+        callback.call(["test/example_test.rb"], [], []) unless thread_count > 2
       end
 
-      run_watcher(in: fixtures_path.join("example_project"))
-
+      run_watcher(iterations: 2, in: fixtures_path.join("example_project"))
       assert_equal(2, thread_count)
     end
 
     private
 
-    class ListenThread
+    class Listener
       def initialize(thread, callback)
         Thread.new do
           thread.call(callback)
@@ -117,14 +110,14 @@ def paused?
       end
     end
 
-    def run_watcher(in: ".", extra_args: [])
+    def run_watcher(iterations:, in: ".", extra_args: [])
       listen_thread = @listen_thread
       file_system = FileSystem.new
-      file_system.define_singleton_method(:listen) { |&callback| ListenThread.new(listen_thread, callback) }
+      file_system.define_singleton_method(:listen) { |&callback| Listener.new(listen_thread, callback) }
       capture_io do
         Dir.chdir(binding.local_variable_get(:in)) do
           @watcher = Watcher.new(extra_args:, file_system:, system_proc: @system_proc)
-          @watcher.run
+          @watcher.run(iterations:)
         end
       end
     end