ref(on-demand): Improve query builder integration

src/sentry/incidents/serializers/alert_rule.py

@@ -6,7 +6,7 @@
 from django.db import router, transaction
 from django.utils import timezone
 from rest_framework import serializers
-from snuba_sdk import Column, Condition, Function, Limit, Op
+from snuba_sdk import Column, Condition, Limit, Op
 
 from sentry import features
 from sentry.api.fields.actor import ActorField
@@ -303,7 +303,7 @@ def _validate_snql_query(self, data, entity_subscription, projects):
         except (InvalidSearchQuery, ValueError) as e:
             raise serializers.ValidationError(f"Invalid Query or Metric: {e}")
 
-        if not isinstance(query_builder.columns[0], Function):
+        if not query_builder.are_columns_resolved():
             raise serializers.ValidationError(
                 "Invalid Metric: Please pass a valid function for aggregation"
             )

src/sentry/search/events/builder/discover.py

@@ -241,6 +241,7 @@ def __init__(
         self.on_demand_metrics_enabled = on_demand_metrics_enabled
         self.auto_fields = auto_fields
         self.query = query
+        self.selected_columns = selected_columns
         self.groupby_columns = groupby_columns
         self.functions_acl = set() if functions_acl is None else functions_acl
         self.equation_config = {} if equation_config is None else equation_config
@@ -309,12 +310,16 @@ def __init__(
             orderby=orderby,
         )
 
+    def are_columns_resolved(self) -> bool:
+        return self.columns and isinstance(self.columns[0], Function)
+
     def get_default_converter(self) -> Callable[[event_search.SearchFilter], Optional[WhereType]]:
         return self._default_filter_converter
 
     def resolve_time_conditions(self) -> None:
         if self.skip_time_conditions:
             return
+
         # start/end are required so that we can run a query in a reasonable amount of time
         if self.params.start is None or self.params.end is None:
             raise InvalidSearchQuery("Cannot query without a valid date range")