[5.2.x] Refs #36042 -- Consolidated composite expression checks in BaseExpression.

Remove redundant Func.resolve_expression and adjust CombinedExpression to
delegate source expression resolving to super() to perform checks against
allows_composite_expressions in a single location.

Backport of a76035e925ff4e6d8676c65cb135c74b993b1039 from main.

django/db/models/expressions.py

@@ -292,16 +292,22 @@ class BaseExpression:
         """
         c = self.copy()
         c.is_summary = summarize
-        c.set_source_expressions(
+        source_expressions = [
-            [
+            (
-                (
+                expr.resolve_expression(query, allow_joins, reuse, summarize)
-                    expr.resolve_expression(query, allow_joins, reuse, summarize)
+                if expr is not None
-                    if expr
+                else None
-                    else None
+            )
-                )
+            for expr in c.get_source_expressions()
-                for expr in c.get_source_expressions()
+        ]
-            ]
+        if not self.allows_composite_expressions and any(
-        )
+            isinstance(expr, ColPairs) for expr in source_expressions
+        ):
+            raise ValueError(
+                f"{self.__class__.__name__} expression does not support "
+                "composite primary keys."
+            )
+        c.set_source_expressions(source_expressions)
         return c
 
     @property
@@ -754,32 +760,25 @@ class CombinedExpression(SQLiteNumericMixin, Expression):
     def resolve_expression(
         self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False
     ):
-        lhs = self.lhs.resolve_expression(
+        resolved = super().resolve_expression(
-            query, allow_joins, reuse, summarize, for_save
+            query,
+            allow_joins,
+            reuse,
+            summarize,
+            for_save,
         )
-        rhs = self.rhs.resolve_expression(
-            query, allow_joins, reuse, summarize, for_save
-        )
-        if isinstance(lhs, ColPairs) or isinstance(rhs, ColPairs):
-            raise ValueError("CompositePrimaryKey is not combinable.")
         if not isinstance(self, (DurationExpression, TemporalSubtraction)):
             try:
-                lhs_type = lhs.output_field.get_internal_type()
+                lhs_type = resolved.lhs.output_field.get_internal_type()
             except (AttributeError, FieldError):
                 lhs_type = None
             try:
-                rhs_type = rhs.output_field.get_internal_type()
+                rhs_type = resolved.rhs.output_field.get_internal_type()
             except (AttributeError, FieldError):
                 rhs_type = None
             if "DurationField" in {lhs_type, rhs_type} and lhs_type != rhs_type:
                 return DurationExpression(
-                    self.lhs, self.connector, self.rhs
+                    resolved.lhs, resolved.connector, resolved.rhs
-                ).resolve_expression(
-                    query,
-                    allow_joins,
-                    reuse,
-                    summarize,
-                    for_save,
                 )
             datetime_fields = {"DateField", "DateTimeField", "TimeField"}
             if (
@@ -787,18 +786,8 @@ class CombinedExpression(SQLiteNumericMixin, Expression):
                 and lhs_type in datetime_fields
                 and lhs_type == rhs_type
             ):
-                return TemporalSubtraction(self.lhs, self.rhs).resolve_expression(
+                return TemporalSubtraction(resolved.lhs, resolved.rhs)
-                    query,
+        return resolved
-                    allow_joins,
-                    reuse,
-                    summarize,
-                    for_save,
-                )
-        c = self.copy()
-        c.is_summary = summarize
-        c.lhs = lhs
-        c.rhs = rhs
-        return c
 
     @cached_property
     def allowed_default(self):
@@ -1070,23 +1059,6 @@ class Func(SQLiteNumericMixin, Expression):
     def set_source_expressions(self, exprs):
         self.source_expressions = exprs
 
-    def resolve_expression(
-        self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False
-    ):
-        c = self.copy()
-        c.is_summary = summarize
-        for pos, arg in enumerate(c.source_expressions):
-            c.source_expressions[pos] = arg.resolve_expression(
-                query, allow_joins, reuse, summarize, for_save
-            )
-        if not self.allows_composite_expressions and any(
-            isinstance(expr, ColPairs) for expr in c.get_source_expressions()
-        ):
-            raise ValueError(
-                f"{self.__class__.__name__} does not support composite primary keys."
-            )
-        return c
-
     def as_sql(
         self,
         compiler,

tests/composite_pk/test_aggregate.py

@@ -138,6 +138,6 @@ class CompositePKAggregateTests(TestCase):
         )
 
     def test_max_pk(self):
-        msg = "Max does not support composite primary keys."
+        msg = "Max expression does not support composite primary keys."
         with self.assertRaisesMessage(ValueError, msg):
             Comment.objects.aggregate(Max("pk"))

tests/composite_pk/test_filter.py

@@ -63,7 +63,7 @@ class CompositePKFilterTests(TestCase):
             Comment.objects.filter(text__gt=F("pk")).count()
 
     def test_rhs_combinable(self):
-        msg = "CompositePrimaryKey is not combinable."
+        msg = "CombinedExpression expression does not support composite primary keys."
         for expr in [F("pk") + (1, 1), (1, 1) + F("pk")]:
             with (
                 self.subTest(expression=expr),
@@ -405,7 +405,7 @@ class CompositePKFilterTests(TestCase):
         self.assertSequenceEqual(queryset, (self.user_2,))
 
     def test_cannot_cast_pk(self):
-        msg = "Cast does not support composite primary keys."
+        msg = "Cast expression does not support composite primary keys."
         with self.assertRaisesMessage(ValueError, msg):
             Comment.objects.filter(text__gt=Cast(F("pk"), TextField())).count()