Improved error message in the from_dict (Azure#19416)

* Improved error message in the `from_dict`

* lint

* spec lin

* tests

* Add AAD support

* eafp

* Revert "Add AAD support"

This reverts commit 1cc83d9.

* language

* lint

sdk/core/azure-core/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## 1.15.1 (Unreleased)
 
+### Bug Fixes
+
+- Improved error message in the `from_dict` method of `CloudEvent` when a wrong schema is sent.
 
 ## 1.15.0 (2021-06-04)
 

sdk/core/azure-core/azure/core/messaging.py

@@ -158,11 +158,26 @@ def from_dict(cls, event):
         if extensions:
             kwargs["extensions"] = extensions
 
-        return cls(
-            id=event.get("id"),
-            source=event["source"],
-            type=event["type"],
-            specversion=event.get("specversion"),
-            time=_convert_to_isoformat(event.get("time")),
-            **kwargs
-        )
+        try:
+            event_obj = cls(
+                id=event.get("id"),
+                source=event["source"],
+                type=event["type"],
+                specversion=event.get("specversion"),
+                time=_convert_to_isoformat(event.get("time")),
+                **kwargs
+            )
+        except KeyError:
+            # https://github.com/cloudevents/spec Cloud event spec requires source, type,
+            # specversion. We autopopulate everything other than source, type.
+            if not all([_ in event for _ in ("source", "type")]):
+                if all([_ in event for _ in ("subject", "eventType", "data", "dataVersion", "id", "eventTime")]):
+                    raise ValueError(
+                        "The event you are trying to parse follows the Eventgrid Schema. You can parse" +
+                        " EventGrid events using EventGridEvent.from_dict method in the azure-eventgrid library."
+                    )
+                raise ValueError(
+                    "The event does not conform to the cloud event spec https://github.com/cloudevents/spec." +
+                    " The `source` and `type` params are required."
+                    )
+        return event_obj

sdk/core/azure-core/tests/test_messaging_cloud_event.py

@@ -436,3 +436,37 @@ def test_cloud_custom_dict_ms_precision_is_eq_six_z_not():
     assert date_obj.day == 18
     assert date_obj.hour == 20
     assert date_obj.microsecond == 123456
+
+def test_eventgrid_event_schema_raises():
+    cloud_custom_dict = {
+        "id":"de0fd76c-4ef4-4dfb-ab3a-8f24a307e033",
+        "data":{"team": "event grid squad"},
+        "dataVersion": "1.0",
+        "subject":"Azure.Sdk.Sample",
+        "eventTime":"2020-08-07T02:06:08.11969Z",
+        "eventType":"pull request",
+    }
+    with pytest.raises(ValueError, match="The event you are trying to parse follows the Eventgrid Schema. You can parse EventGrid events using EventGridEvent.from_dict method in the azure-eventgrid library."):
+        CloudEvent.from_dict(cloud_custom_dict)
+
+def test_wrong_schema_raises_no_source():
+    cloud_custom_dict = {
+        "id":"de0fd76c-4ef4-4dfb-ab3a-8f24a307e033",
+        "data":{"team": "event grid squad"},
+        "type":"Azure.Sdk.Sample",
+        "time":"2020-08-07T02:06:08.11969Z",
+        "specversion":"1.0",
+    }
+    with pytest.raises(ValueError, match="The event does not conform to the cloud event spec https://github.com/cloudevents/spec. The `source` and `type` params are required."):
+        CloudEvent.from_dict(cloud_custom_dict)
+
+def test_wrong_schema_raises_no_type():
+    cloud_custom_dict = {
+        "id":"de0fd76c-4ef4-4dfb-ab3a-8f24a307e033",
+        "data":{"team": "event grid squad"},
+        "source":"Azure/Sdk/Sample",
+        "time":"2020-08-07T02:06:08.11969Z",
+        "specversion":"1.0",
+    }
+    with pytest.raises(ValueError, match="The event does not conform to the cloud event spec https://github.com/cloudevents/spec. The `source` and `type` params are required."):
+        CloudEvent.from_dict(cloud_custom_dict)