feat: add IsEventQLTrue precondition and corresponding tests

Author: matthiasharzer

eventsourcingdb/__init__.py

@@ -10,7 +10,7 @@
 )
 from .read_events import ReadEventsOptions, ReadFromLatestEvent, IfEventIsMissingDuringRead, Order
 from .read_event_types import EventType
-from .write_events import Precondition, IsSubjectOnEventId, IsSubjectPristine
+from .write_events import Precondition, IsSubjectOnEventId, IsSubjectPristine, IsEventQLTrue
 
 
 __all__ = [
@@ -20,7 +20,7 @@
     'Event', 'EventCandidate',
     'EventType',
     'ObserveEventsOptions', 'ObserveFromLatestEvent', 'IfEventIsMissingDuringObserve',
-    'Precondition', 'IsSubjectOnEventId', 'IsSubjectPristine',
+    'Precondition', 'IsSubjectOnEventId', 'IsSubjectPristine', 'IsEventQLTrue',
     'ReadEventsOptions', 'ReadFromLatestEvent', 'IfEventIsMissingDuringRead', 'Order',
     'ClientError', 'CustomError', 'InternalError', 'ServerError', 'ValidationError',
 ]

eventsourcingdb/write_events/__init__.py

@@ -1,3 +1,4 @@
 from .preconditions import Precondition
 from .preconditions import IsSubjectPristine
 from .preconditions import IsSubjectOnEventId
+from .preconditions import IsEventQLTrue

eventsourcingdb/write_events/preconditions.py

@@ -35,3 +35,15 @@ def to_json(self) -> dict[str, Any]:
                 'eventId': self.event_id
             }
         }
+
+@dataclass
+class IsEventQLTrue(Precondition):
+    query: str
+
+    def to_json(self) -> dict[str, Any]:
+        return {
+            'type': 'isEventQLTrue',
+            'payload': {
+                'query': self.query
+            }
+        }

tests/test_write_events.py

@@ -4,6 +4,7 @@
 from eventsourcingdb import ServerError
 from eventsourcingdb import EventCandidate
 from eventsourcingdb import IsSubjectPristine, IsSubjectOnEventId
+from eventsourcingdb.write_events.preconditions import IsEventQLTrue
 
 from .conftest import TestData
 
@@ -215,6 +216,69 @@ async def test_is_subject_on_event_id_fails_for_wrong_id(
                 [IsSubjectOnEventId('/', '2')]
             )
 
+    @staticmethod
+    @pytest.mark.asyncio
+    async def test_is_event_ql_true_precondition_works(
+        database: Database,
+        test_data: TestData,
+    ) -> None:
+        client = database.get_client()
+
+        await client.write_events(
+            [
+                EventCandidate(
+                    source=test_data.TEST_SOURCE_STRING,
+                    subject='/',
+                    type='com.foo.bar',
+                    data={}
+                )
+            ]
+        )
+
+        await client.write_events(
+            [
+                EventCandidate(
+                    source=test_data.TEST_SOURCE_STRING,
+                    subject='/',
+                    type='com.foo.bar',
+                    data={}
+                )
+            ],
+            [IsEventQLTrue('FROM e IN events PROJECT INTO COUNT() > 0')]
+        )
+
+    @staticmethod
+    @pytest.mark.asyncio
+    async def test_is_event_ql_true_precondition_fails(
+        database: Database,
+        test_data: TestData,
+    ) -> None:
+        client = database.get_client()
+
+        await client.write_events(
+            [
+                EventCandidate(
+                    source=test_data.TEST_SOURCE_STRING,
+                    subject='/',
+                    type='com.foo.bar',
+                    data={}
+                )
+            ]
+        )
+
+        with pytest.raises(ServerError):
+            await client.write_events(
+                [
+                    EventCandidate(
+                        source=test_data.TEST_SOURCE_STRING,
+                        subject='/',
+                        type='com.foo.bar',
+                        data={}
+                    )
+                ],
+                [IsEventQLTrue('FROM e IN events PROJECT INTO COUNT() == 0')]
+            )
+
     @staticmethod
     @pytest.mark.asyncio
     async def test_throws_error_if_event_does_not_match_schema(