fix(issues): Attribute error in issue details thrown on None tag values

src/sentry/api/endpoints/organization_spans_fields.py

@@ -184,7 +184,7 @@ def get(self, request: Request, organization: Organization, key: str) -> Respons
         with handle_query_errors():
             tag_values = executor.execute()
 
-        tag_values.sort(key=lambda tag: tag.value)
+        tag_values.sort(key=lambda tag: tag.value or "")
 
         paginator = ChainPaginator([tag_values], max_limit=max_span_tag_values)
 

src/sentry/api/endpoints/organization_trace_item_attributes.py

@@ -375,7 +375,7 @@ def data_fn(offset: int, limit: int):
 
             with handle_query_errors():
                 tag_values = executor.execute()
-            tag_values.sort(key=lambda tag: tag.value)
+            tag_values.sort(key=lambda tag: tag.value or "")
             return tag_values
 
         return self.paginate(

src/sentry/data_export/processors/issues_by_tag.py

@@ -113,7 +113,12 @@ def get_raw_data(self, limit: int = 1000, offset: int = 0) -> list[GroupTagValue
             users = EventUser.for_tags(self.group.project_id, [i.value for i in items])
         else:
             users = {}
-        return [GroupTagValueAndEventUser(item, users.get(item.value)) for item in items]
+        return [
+            GroupTagValueAndEventUser(
+                item, users.get(item.value) if item.value is not None else None
+            )
+            for item in items
+        ]
 
     def get_serialized_data(self, limit: int = 1000, offset: int = 0) -> list[dict[str, str]]:
         """

src/sentry/search/utils.py

@@ -831,7 +831,7 @@ def convert_user_tag_to_query(key: str, value: str) -> str | None:
     Converts a user tag to a query string that can be used to search for that
     user. Returns None if not a user tag.
     """
-    if key == "user" and ":" in value:
+    if key == "user" and value is not None and ":" in value:
         sub_key, value = value.split(":", 1)
         if KEYWORD_MAP.get_key(sub_key, None):
             return 'user.{}:"{}"'.format(sub_key, value.replace('"', '\\"'))

src/sentry/tagstore/types.py

@@ -29,7 +29,16 @@ def __eq__(self, other: object) -> bool:
         )
 
     def __lt__(self, other: object) -> bool:
-        return getattr(self, self._sort_key) < getattr(other, self._sort_key)
+        self_val = getattr(self, self._sort_key)
+        other_val = getattr(other, self._sort_key)
+        # Handle None values in sorting - None sorts before any non-None value
+        if self_val is None and other_val is None:
+            return False
+        if self_val is None:
+            return True
+        if other_val is None:
+            return False
+        return self_val < other_val
 
     def __getstate__(self) -> dict[str, Any]:
         return {name: getattr(self, name) for name in self.__slots__}
@@ -68,7 +77,7 @@ class TagValue(TagType):
     def __init__(
         self,
         key: str,
-        value,
+        value: str | None,
         times_seen: int | None,
         first_seen: datetime | None,
         last_seen: datetime | None,
@@ -107,7 +116,7 @@ def __init__(
         self,
         group_id: int,
         key: str,
-        value,
+        value: str | None,
         times_seen: int,
         first_seen,
         last_seen,

src/sentry/utils/eventuser.py

@@ -314,7 +314,7 @@ def from_snuba(result: Mapping[str, Any]) -> EventUser:
 
     @classmethod
     def for_tags(
-        cls: type[EventUser], project_id: int, values: Sequence[str]
+        cls: type[EventUser], project_id: int, values: Sequence[str | None]
     ) -> dict[str, EventUser]:
         """
         Finds matching EventUser objects from a list of tag values.
@@ -338,14 +338,18 @@ def for_tags(
 
     @classmethod
     def _process_tag_batch(
-        cls, projects: QuerySet[Project], values: Sequence[str]
+        cls, projects: QuerySet[Project], values: Sequence[str | None]
     ) -> dict[str, EventUser]:
         """
         Process a single batch of tag values and return the matching EventUser objects.
         """
         result = {}
         keyword_filters: dict[str, Any] = {}
         for value in values:
+            # Skip None values - these represent events without the tag set.
+            # There's no EventUser to look up for these cases.
+            if value is None:
+                continue
             key, value = value.split(":", 1)[0], value.split(":", 1)[-1]
             if keyword_filters.get(key):
                 keyword_filters[key].append(value)

tests/sentry/issues/endpoints/test_group_tagkey_values.py

@@ -210,6 +210,39 @@ def test_includes_empty_values_backend_helpers(self) -> None:
         assert values.get("bar") == 1
         assert values.get("") == 1
 
+    def test_user_tag_with_empty_values(self) -> None:
+        """Test that user tags with empty values don't cause AttributeError."""
+        project = self.create_project()
+
+        # Event with user data
+        self.store_event(
+            data={
+                "user": {"id": "user123"},
+                "timestamp": before_now(seconds=1).isoformat(),
+            },
+            project_id=project.id,
+        )
+        # Event without user data (will have empty user tag)
+        event = self.store_event(
+            data={
+                "timestamp": before_now(seconds=2).isoformat(),
+            },
+            project_id=project.id,
+        )
+
+        group = event.group
+
+        self.login_as(user=self.user)
+
+        url = f"/api/0/issues/{group.id}/tags/user/values/"
+
+        # This should not crash with AttributeError: 'NoneType' object has no attribute 'split'
+        response = self.client.get(url)
+
+        assert response.status_code == 200
+        # Should return at least the user with id, empty values may or may not be included
+        assert len(response.data) >= 1
+
     def test_count_sort(self) -> None:
         project = self.create_project()
         project.date_added = timezone.now() - timedelta(minutes=10)