Watcher: if we're already stale, no need to keep listening for changes

lib/spring/watcher/listen.rb

@@ -21,6 +21,11 @@ class Listen < Abstract
 
       attr_reader :listener
 
+      def initialize(*)
+        super
+        @listener = nil
+      end
+
       def start
         unless @listener
           @listener = ::Listen.to(*base_directories, latency: latency, &method(:changed))
@@ -35,6 +40,10 @@ def stop
         end
       end
 
+      def running?
+        @listener && @listener.processing?
+      end
+
       def subjects_changed
         return unless @listener
         return unless @listener.respond_to?(:directories)
@@ -54,6 +63,14 @@ def changed(modified, added, removed)
         end
       end
 
+      def mark_stale
+        super
+
+        # May be called from listen thread which won't be happy
+        # about stopping itself, so stop from another thread.
+        Thread.new { stop }.join
+      end
+
       def base_directories
         ([root] +
           files.reject       { |f| f.start_with? "#{root}/" }.map { |f| File.expand_path("#{f}/..") } +

test/unit_test.rb

@@ -53,4 +53,22 @@ def watcher_class
       FileUtils.rmdir other_dir_2
     end
   end
+
+  test "stops listening when already stale" do
+    # Track when we're marked as stale.
+    on_stale_count = 0
+    watcher.on_stale { on_stale_count += 1 }
+
+    # Add a file to watch and start listening.
+    file = "#{@dir}/omg"
+    touch file, Time.now - 2.seconds
+    watcher.add file
+    watcher.start
+    assert watcher.running?
+
+    # Touch bumps mtime and marks as stale which stops listener.
+    touch file, Time.now - 1.second
+    Timeout.timeout(1) { sleep 0.1 while watcher.running? }
+    assert_equal 1, on_stale_count
+  end
 end