Fixed #33766 -- Resolved FilteredRelation.condition at referencing time.

The previous implementation resolved condition at Join compilation time
which required introducing a specialized expression resolving mode to
alter the join reuse logic solely during that phase.

FilteredRelation.condition is now resolved when the relation is first
referenced which maintains the existing behavior while allowing the
removal of the specialized resolving mode and address an issue where
conditions couldn't spawn new joins.

3 files changed, 58 insertions, 48 deletions

diff --git a/django/db/models/query_utils.py b/django/db/models/query_utils.py
index a82ed23dbb..52b472d252 100644
--- a/django/db/models/query_utils.py
+++ b/django/db/models/query_utils.py
@@ -403,8 +403,11 @@ class FilteredRelation:
         self.alias = None
         if not isinstance(condition, Q):
             raise ValueError("condition argument must be a Q() instance.")
+        # .condition and .resolved_condition have to be stored independently
+        # as the former must remain unchanged for Join.__eq__ to remain stable
+        # and reusable even once their .filtered_relation are resolved.
         self.condition = condition
-        self.path = []
+        self.resolved_condition = None
 
     def __eq__(self, other):
         if not isinstance(other, self.__class__):
@@ -418,18 +421,22 @@ class FilteredRelation:
     def clone(self):
         clone = FilteredRelation(self.relation_name, condition=self.condition)
         clone.alias = self.alias
-        clone.path = self.path[:]
+        if (resolved_condition := self.resolved_condition) is not None:
+            clone.resolved_condition = resolved_condition.clone()
         return clone
 
-    def resolve_expression(self, *args, **kwargs):
-        """
-        QuerySet.annotate() only accepts expression-like arguments
-        (with a resolve_expression() method).
-        """
-        raise NotImplementedError("FilteredRelation.resolve_expression() is unused.")
+    def relabeled_clone(self, change_map):
+        clone = self.clone()
+        if resolved_condition := clone.resolved_condition:
+            clone.resolved_condition = resolved_condition.relabeled_clone(change_map)
+        return clone
+
+    def resolve_expression(self, query, reuse, *args, **kwargs):
+        clone = self.clone()
+        clone.resolved_condition = query.build_filtered_relation_q(
+            self.condition, reuse=reuse
+        )
+        return clone
 
     def as_sql(self, compiler, connection):
-        # Resolve the condition in Join.filtered_relation.
-        query = compiler.query
-        where = query.build_filtered_relation_q(self.condition, reuse=set(self.path))
-        return compiler.compile(where)
+        return compiler.compile(self.resolved_condition)
diff --git a/django/db/models/sql/datastructures.py b/django/db/models/sql/datastructures.py
index dadd7c063d..a88bc09593 100644
--- a/django/db/models/sql/datastructures.py
+++ b/django/db/models/sql/datastructures.py
@@ -154,10 +154,7 @@ class Join:
         new_parent_alias = change_map.get(self.parent_alias, self.parent_alias)
         new_table_alias = change_map.get(self.table_alias, self.table_alias)
         if self.filtered_relation is not None:
-            filtered_relation = self.filtered_relation.clone()
-            filtered_relation.path = [
-                change_map.get(p, p) for p in self.filtered_relation.path
-            ]
+            filtered_relation = self.filtered_relation.relabeled_clone(change_map)
         else:
             filtered_relation = None
         return self.__class__(
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 2ffcfaa10c..24e08ae6a6 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -73,6 +73,19 @@ def get_children_from_q(q):
             yield child
 
 
+def rename_prefix_from_q(prefix, replacement, q):
+    return Q.create(
+        [
+            rename_prefix_from_q(prefix, replacement, c)
+            if isinstance(c, Node)
+            else (c[0].replace(prefix, replacement, 1), c[1])
+            for c in q.children
+        ],
+        q.connector,
+        q.negated,
+    )
+
+
 JoinInfo = namedtuple(
     "JoinInfo",
     ("final_field", "targets", "opts", "joins", "path", "transform_function"),
@@ -994,7 +1007,7 @@ class Query(BaseExpression):
         """
         return len([1 for count in self.alias_refcount.values() if count])
 
-    def join(self, join, reuse=None, reuse_with_filtered_relation=False):
+    def join(self, join, reuse=None):
         """
         Return an alias for the 'join', either reusing an existing alias for
         that join or creating a new one. 'join' is either a base_table_class or
@@ -1003,23 +1016,15 @@ class Query(BaseExpression):
         The 'reuse' parameter can be either None which means all joins are
         reusable, or it can be a set containing the aliases that can be reused.
 
-        The 'reuse_with_filtered_relation' parameter is used when computing
-        FilteredRelation instances.
-
         A join is always created as LOUTER if the lhs alias is LOUTER to make
         sure chains like t1 LOUTER t2 INNER t3 aren't generated. All new
         joins are created as LOUTER if the join is nullable.
         """
-        if reuse_with_filtered_relation and reuse:
-            reuse_aliases = [
-                a for a, j in self.alias_map.items() if a in reuse and j.equals(join)
-            ]
-        else:
-            reuse_aliases = [
-                a
-                for a, j in self.alias_map.items()
-                if (reuse is None or a in reuse) and j == join
-            ]
+        reuse_aliases = [
+            a
+            for a, j in self.alias_map.items()
+            if (reuse is None or a in reuse) and j == join
+        ]
         if reuse_aliases:
             if join.table_alias in reuse_aliases:
                 reuse_alias = join.table_alias
@@ -1042,6 +1047,18 @@ class Query(BaseExpression):
             join.join_type = join_type
         join.table_alias = alias
         self.alias_map[alias] = join
+        if filtered_relation := join.filtered_relation:
+            resolve_reuse = reuse
+            if resolve_reuse is not None:
+                resolve_reuse = set(reuse) | {alias}
+            joins_len = len(self.alias_map)
+            join.filtered_relation = filtered_relation.resolve_expression(
+                self, reuse=resolve_reuse
+            )
+            # Some joins were during expression resolving, they must be present
+            # before the one we just added.
+            if joins_len < len(self.alias_map):
+                self.alias_map[alias] = self.alias_map.pop(alias)
         return alias
 
     def join_parent_model(self, opts, model, alias, seen):
@@ -1328,7 +1345,6 @@ class Query(BaseExpression):
         can_reuse=None,
         allow_joins=True,
         split_subq=True,
-        reuse_with_filtered_relation=False,
         check_filterable=True,
         summarize=False,
     ):
@@ -1353,9 +1369,6 @@ class Query(BaseExpression):
 
         The 'can_reuse' is a set of reusable joins for multijoins.
 
-        If 'reuse_with_filtered_relation' is True, then only joins in can_reuse
-        will be reused.
-
         The method will create a filter clause that can be added to the current
         query. However, if the filter isn't added to the query then the caller
         is responsible for unreffing the joins used.
@@ -1417,7 +1430,6 @@ class Query(BaseExpression):
                 alias,
                 can_reuse=can_reuse,
                 allow_many=allow_many,
-                reuse_with_filtered_relation=reuse_with_filtered_relation,
             )
 
             # Prevent iterator from being consumed by check_related_objects()
@@ -1575,7 +1587,6 @@ class Query(BaseExpression):
                     current_negated=current_negated,
                     allow_joins=True,
                     split_subq=False,
-                    reuse_with_filtered_relation=True,
                 )
             target_clause.add(child_clause, connector)
         return target_clause
@@ -1609,6 +1620,11 @@ class Query(BaseExpression):
                         "relations deeper than the relation_name (got %r for "
                         "%r)." % (lookup, filtered_relation.relation_name)
                     )
+        filtered_relation.condition = rename_prefix_from_q(
+            filtered_relation.relation_name,
+            alias,
+            filtered_relation.condition,
+        )
         self._filtered_relations[filtered_relation.alias] = filtered_relation
 
     def names_to_path(self, names, opts, allow_many=True, fail_on_missing=False):
@@ -1734,7 +1750,6 @@ class Query(BaseExpression):
         alias,
         can_reuse=None,
         allow_many=True,
-        reuse_with_filtered_relation=False,
     ):
         """
         Compute the necessary table joins for the passage through the fields
@@ -1747,9 +1762,6 @@ class Query(BaseExpression):
         that can be reused. Note that non-reverse foreign keys are always
         reusable when using setup_joins().
 
-        The 'reuse_with_filtered_relation' can be used to force 'can_reuse'
-        parameter and force the relation on the given connections.
-
         If 'allow_many' is False, then any reverse foreign key seen will
         generate a MultiJoin exception.
 
@@ -1841,15 +1853,9 @@ class Query(BaseExpression):
                 nullable,
                 filtered_relation=filtered_relation,
             )
-            reuse = can_reuse if join.m2m or reuse_with_filtered_relation else None
-            alias = self.join(
-                connection,
-                reuse=reuse,
-                reuse_with_filtered_relation=reuse_with_filtered_relation,
-            )
+            reuse = can_reuse if join.m2m else None
+            alias = self.join(connection, reuse=reuse)
             joins.append(alias)
-            if filtered_relation:
-                filtered_relation.path = joins[:]
         return JoinInfo(final_field, targets, opts, joins, path, final_transformer)
 
     def trim_joins(self, targets, joins, path):