Allow to call FSEventsEmitter.stop() twice without error

AUTHORS

@@ -13,6 +13,7 @@ Gary van der Merwe <garyvdm@garyvdm.localdomain>
 Gora Khargosh <gora.khargosh@gmail.com>
 Hannu Valtonen <hannu.valtonen@ohmu.fi>
 Jesse Printz <jesse@jonypawks.net>
+Léa Klein <lklein@nuxeo.com>
 Luke McCarthy <luke@iogopro.co.uk>
 Lukáš Lalinský <lalinsky@gmail.com>
 Malthe Borch <mborch@gmail.com>

src/watchdog/observers/fsevents.py

@@ -73,8 +73,10 @@ def __init__(self, event_queue, watch, timeout=DEFAULT_EMITTER_TIMEOUT):
         self.snapshot = DirectorySnapshot(watch.path, watch.is_recursive)
 
     def on_thread_stop(self):
-        _fsevents.remove_watch(self.watch)
-        _fsevents.stop(self)
+        if self.watch:
+            _fsevents.remove_watch(self.watch)
+            _fsevents.stop(self)
+            self._watch = None
 
     def queue_events(self, timeout):
         with self._lock:

tests/test_fsevents.py

@@ -0,0 +1,64 @@
+# coding: utf-8
+import logging
+import os
+from functools import partial
+
+import pytest
+
+from watchdog.observers.api import ObservedWatch
+from tests import Queue
+
+try:
+    from watchdog.observers.fsevents import FSEventsEmitter
+except ImportError:
+    pytestmark = pytest.mark.skip("macOS only.")
+
+from .shell import mkdtemp, rm
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+def setup_function(function):
+    global p, event_queue
+    tmpdir = os.path.realpath(mkdtemp())
+    p = partial(os.path.join, tmpdir)
+    event_queue = Queue()
+
+
+def teardown_function(function):
+    emitter.stop()
+    emitter.join(5)
+    rm(p(""), recursive=True)
+    assert not emitter.is_alive()
+
+
+def start_watching(path=None, use_full_emitter=False):
+    global emitter
+    path = p("") if path is None else path
+    emitter = FSEventsEmitter(event_queue, ObservedWatch(path, recursive=True))
+    emitter.start()
+
+
+def test_remove_watch_twice():
+    """
+ValueError: PyCapsule_GetPointer called with invalid PyCapsule object
+The above exception was the direct cause of the following exception:
+
+src/watchdog/utils/__init__.py:92: in stop
+    self.on_thread_stop()
+
+src/watchdog/observers/fsevents.py:73: SystemError
+    def on_thread_stop(self):
+>       _fsevents.remove_watch(self.watch)
+E       SystemError: <built-in function remove_watch> returned a result with an error set
+
+(FSEvents.framework) FSEventStreamStop(): failed assertion 'streamRef != NULL'
+(FSEvents.framework) FSEventStreamInvalidate(): failed assertion 'streamRef != NULL'
+(FSEvents.framework) FSEventStreamRelease(): failed assertion 'streamRef != NULL'
+    """
+    start_watching()
+    # This one must work
+    emitter.stop()
+    # This is allowed to call several times .stop()
+    emitter.stop()