Merge pull request #95 from marier-nico/feat/dyn-filter-modifies-event

fix: avoid updating event when filter does not match

docs/content/changelog.rst

@@ -1,3 +1,6 @@
+- v3.2.0: Allow ``Dyn`` filters to modify the event.
+- v3.1.6: Fix type hints with ``Depends``.
+- v3.1.5: Add py.typed file to support type hints.
 - v3.1.4: Simplify calling processors by making ``EventProcessor`` callable.
 - v3.1.3: Fix a bug with invocation when an event matches several filters.
 - v3.1.2: Fix an incorrect import.

docs/content/filters.rst

@@ -223,7 +223,8 @@ be valid for a dependency (see :ref:`Dependencies` for details). For example :
     False
 
 Since the Dyn filter is basically a way to do anything you can't do with static filters, it also allows modifying the
-event before it gets passed to a processor function. For example :
+event before it gets passed to a processor function. Note that the event is only modified if the value returned by the
+dynamic function is truthy (i.e. event is unmodified if the filter doesn't match). For example :
 
 .. testcode::
 

src/event_processor/filters.py

@@ -221,10 +221,11 @@ def matches(self, event: dict) -> bool:
         else:
             result = call_with_injection(self.resolver, event=Event(event), cache={})
 
-        if self.inject_as:
+        matches = bool(result)
+        if self.inject_as and matches:
             event[self.inject_as] = result
 
-        return bool(result)
+        return matches
 
     def __hash__(self):
         return hash(self.resolver)

src/tests/test_filters.py

@@ -476,7 +476,7 @@ def dyn_filter():
     assert hash(filter_) == hash(dyn_filter)
 
 
-def test_dyn_filter_updates_event_when_inject_as_is_specified():
+def test_dyn_filter_updates_event_when_inject_as_is_specified_and_filter_matches():
     mock_event = {}
     filter_ = Dyn(lambda e: "my-value", inject_as="my-key")
 
@@ -485,6 +485,15 @@ def test_dyn_filter_updates_event_when_inject_as_is_specified():
     assert mock_event["my-key"] == "my-value"
 
 
+def test_dyn_filter_does_not_update_event_when_inject_as_is_specified_and_filter_does_not_match():
+    mock_event = {}
+    filter_ = Dyn(lambda e: False, inject_as="my-key")
+
+    filter_.matches(mock_event)
+
+    assert "my-key" not in mock_event
+
+
 def test_eq_filter_matches_when_resolvers_are_equal():
     mock_resolver = Mock()