[mac] Add support for non-recursive watches in FSEventsEmitter (#779)

* Add support for non-recursive watches in FSEventsEmitter

The underlying `fseventsd` service always observes recursively. As such we're adding a filter in `FSEventEmitter` to support the non-recursive behaviour that is supported by other emitters.

* Add more test cases

Test a few more scenarios for non-recursive watches. Do note that at least on macOS we'll get a `DirModifiedEvent` for the created subdirectory.

* Update changelog

* Limit new test scenarios to macOS

We're fixing a defect on macOS after all, and addressing the failures on other platforms looks like opening a can of worms that is not related to the original issue.

* Add tests for move events

changelog.rst

@@ -8,8 +8,8 @@ Changelog
 
 2021-0x-xx • `full history <https://github.com/gorakhargosh/watchdog/compare/v2.0.3...master>`__
 
--
-- Thanks to our beloved contributors: @
+- [mac] Add support for non-recursive watches in FSEventsEmitter (`#779 <https://github.com/gorakhargosh/watchdog/pull/779>`_)
+- Thanks to our beloved contributors: @CCP-Aporia, @
 
 
 2.0.3

src/watchdog/observers/fsevents.py

@@ -92,8 +92,31 @@ def on_thread_stop(self):
             self._watch = None
 
     def queue_event(self, event):
-        logger.debug("queue_event %s", event)
-        EventEmitter.queue_event(self, event)
+        # fsevents defaults to be recursive, so if the watch was meant to be non-recursive then we need to drop
+        # all the events here which do not have a src_path / dest_path that matches the watched path
+        if self._watch.is_recursive:
+            logger.debug("queue_event %s", event)
+            EventEmitter.queue_event(self, event)
+        else:
+            if not self._is_recursive_event(event):
+                logger.debug("queue_event %s", event)
+                EventEmitter.queue_event(self, event)
+            else:
+                logger.debug("drop event %s", event)
+
+    def _is_recursive_event(self, event):
+        src_path = event.src_path if event.is_directory else os.path.dirname(event.src_path)
+        if src_path == self._watch.path:
+            return False
+
+        if isinstance(event, (FileMovedEvent, DirMovedEvent)):
+            # when moving something into the watch path we must always take the dirname,
+            # otherwise we miss out on `DirMovedEvent`s
+            dest_path = os.path.dirname(event.dest_path)
+            if dest_path == self._watch.path:
+                return False
+
+        return True
 
     def _queue_created_event(self, event, src_path, dirname):
         cls = DirCreatedEvent if event.is_directory else FileCreatedEvent

tests/test_emitter.py

@@ -419,7 +419,6 @@ def test_recursive_on():
 
 
 @pytest.mark.flaky(max_runs=5, min_passes=1, rerun_filter=rerun_filter)
-@pytest.mark.skipif(platform.is_darwin(), reason="macOS watches are always recursive")
 def test_recursive_off():
     mkdir(p('dir1'))
     start_watching(recursive=False)
@@ -428,6 +427,34 @@ def test_recursive_off():
     with pytest.raises(Empty):
         event_queue.get(timeout=5)
 
+    mkfile(p('b'))
+    expect_event(FileCreatedEvent(p('b')))
+    if not platform.is_windows():
+        expect_event(DirModifiedEvent(p()))
+
+        if platform.is_linux():
+            expect_event(FileClosedEvent(p('b')))
+
+    # currently limiting these additional events to macOS only, see https://github.com/gorakhargosh/watchdog/pull/779
+    if platform.is_darwin():
+        mkdir(p('dir1', 'dir2'))
+        with pytest.raises(Empty):
+            event_queue.get(timeout=5)
+        mkfile(p('dir1', 'dir2', 'somefile'))
+        with pytest.raises(Empty):
+            event_queue.get(timeout=5)
+
+        mkdir(p('dir3'))
+        expect_event(DirModifiedEvent(p()))  # the contents of the parent directory changed
+
+        mv(p('dir1', 'dir2', 'somefile'), p('somefile'))
+        expect_event(FileMovedEvent(p('dir1', 'dir2', 'somefile'), p('somefile')))
+        expect_event(DirModifiedEvent(p()))
+
+        mv(p('dir1', 'dir2'), p('dir2'))
+        expect_event(DirMovedEvent(p('dir1', 'dir2'), p('dir2')))
+        expect_event(DirModifiedEvent(p()))
+
 
 @pytest.mark.skipif(platform.is_windows(),
                     reason="Windows create another set of events for this test")