[1.8.x] Fixed #24154 -- Backends can now check support for expressions

Backport of 8196e4bdf498acb05e6680c81f9d7bf700f4295c from master

2 files changed, 16 insertions, 10 deletions

diff --git a/django/db/backends/sqlite3/features.py b/django/db/backends/sqlite3/features.py
index fa5a002603..ee86469177 100644
--- a/django/db/backends/sqlite3/features.py
+++ b/django/db/backends/sqlite3/features.py
@@ -60,7 +60,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         """Confirm support for STDDEV and related stats functions
 
         SQLite supports STDDEV as an extension package; so
-        connection.ops.check_aggregate_support() can't unilaterally
+        connection.ops.check_expression_support() can't unilaterally
         rule out support for STDDEV. We need to manually check
         whether the call works.
         """
diff --git a/django/db/backends/sqlite3/operations.py b/django/db/backends/sqlite3/operations.py
index ad05f88585..cd29092cd7 100644
--- a/django/db/backends/sqlite3/operations.py
+++ b/django/db/backends/sqlite3/operations.py
@@ -4,7 +4,7 @@ import datetime
 import uuid
 
 from django.conf import settings
-from django.core.exceptions import ImproperlyConfigured
+from django.core.exceptions import ImproperlyConfigured, FieldError
 from django.db import utils
 from django.db.backends import utils as backend_utils
 from django.db.backends.base.operations import BaseDatabaseOperations
@@ -33,15 +33,21 @@ class DatabaseOperations(BaseDatabaseOperations):
         limit = 999 if len(fields) > 1 else 500
         return (limit // len(fields)) if len(fields) > 0 else len(objs)
 
-    def check_aggregate_support(self, aggregate):
+    def check_expression_support(self, expression):
         bad_fields = (fields.DateField, fields.DateTimeField, fields.TimeField)
-        bad_aggregates = (aggregates.Sum, aggregates.Avg,
-                          aggregates.Variance, aggregates.StdDev)
-        if aggregate.refs_field(bad_aggregates, bad_fields):
-            raise NotImplementedError(
-                'You cannot use Sum, Avg, StdDev and Variance aggregations '
-                'on date/time fields in sqlite3 '
-                'since date/time is saved as text.')
+        bad_aggregates = (aggregates.Sum, aggregates.Avg, aggregates.Variance, aggregates.StdDev)
+        if isinstance(expression, bad_aggregates):
+            try:
+                output_field = expression.input_field.output_field
+                if isinstance(output_field, bad_fields):
+                    raise NotImplementedError(
+                        'You cannot use Sum, Avg, StdDev and Variance aggregations '
+                        'on date/time fields in sqlite3 '
+                        'since date/time is saved as text.')
+            except FieldError:
+                # not every sub-expression has an output_field which is fine to
+                # ignore
+                pass
 
     def date_extract_sql(self, lookup_type, field_name):
         # sqlite doesn't support extract, so we fake it with the user-defined