Fixed #31956 -- Fixed crash of ordering by JSONField with a custom decoder on PostgreSQL.

Thanks Marc Debureaux for the report.
Thanks Simon Charette, Nick Pope, and Adam Johnson for reviews.

5 files changed, 5 insertions, 22 deletions

diff --git a/django/contrib/postgres/aggregates/general.py b/django/contrib/postgres/aggregates/general.py
index f78eed7a60..ea94ab282a 100644
--- a/django/contrib/postgres/aggregates/general.py
+++ b/django/contrib/postgres/aggregates/general.py
@@ -48,7 +48,7 @@ class JSONBAgg(OrderableAggMixin, Aggregate):
 
     def convert_value(self, value, expression, connection):
         if not value:
-            return []
+            return '[]'
         return value
 
 
diff --git a/django/db/backends/base/operations.py b/django/db/backends/base/operations.py
index 617ac95907..d8496f7e2c 100644
--- a/django/db/backends/base/operations.py
+++ b/django/db/backends/base/operations.py
@@ -153,13 +153,6 @@ class BaseDatabaseOperations:
         """
         return self.date_extract_sql(lookup_type, field_name)
 
-    def json_cast_text_sql(self, field_name):
-        """Return the SQL to cast a JSON value to text value."""
-        raise NotImplementedError(
-            'subclasses of BaseDatabaseOperations may require a '
-            'json_cast_text_sql() method'
-        )
-
     def deferrable_sql(self):
         """
         Return the SQL to make a constraint "initially deferred" during a
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index ed911a91da..03c7a3c284 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -200,7 +200,10 @@ class DatabaseWrapper(BaseDatabaseWrapper):
             # Set the isolation level to the value from OPTIONS.
             if self.isolation_level != connection.isolation_level:
                 connection.set_session(isolation_level=self.isolation_level)
-
+        # Register dummy loads() to avoid a round trip from psycopg2's decode
+        # to json.dumps() to json.loads(), when using a custom decoder in
+        # JSONField.
+        psycopg2.extras.register_default_jsonb(conn_or_curs=connection, loads=lambda x: x)
         return connection
 
     def ensure_timezone(self):
diff --git a/django/db/backends/postgresql/operations.py b/django/db/backends/postgresql/operations.py
index a3442231af..1ce5755bf5 100644
--- a/django/db/backends/postgresql/operations.py
+++ b/django/db/backends/postgresql/operations.py
@@ -74,9 +74,6 @@ class DatabaseOperations(BaseDatabaseOperations):
     def time_trunc_sql(self, lookup_type, field_name):
         return "DATE_TRUNC('%s', %s)::time" % (lookup_type, field_name)
 
-    def json_cast_text_sql(self, field_name):
-        return '(%s)::text' % field_name
-
     def deferrable_sql(self):
         return " DEFERRABLE INITIALLY DEFERRED"
 
diff --git a/django/db/models/fields/json.py b/django/db/models/fields/json.py
index 00df1ae206..a249f4cdbf 100644
--- a/django/db/models/fields/json.py
+++ b/django/db/models/fields/json.py
@@ -70,8 +70,6 @@ class JSONField(CheckFieldDefaultMixin, Field):
     def from_db_value(self, value, expression, connection):
         if value is None:
             return value
-        if connection.features.has_native_json_field and self.decoder is None:
-            return value
         try:
             return json.loads(value, cls=self.decoder)
         except json.JSONDecodeError:
@@ -91,14 +89,6 @@ class JSONField(CheckFieldDefaultMixin, Field):
             return transform
         return KeyTransformFactory(name)
 
-    def select_format(self, compiler, sql, params):
-        if (
-            compiler.connection.features.has_native_json_field and
-            self.decoder is not None
-        ):
-            return compiler.connection.ops.json_cast_text_sql(sql), params
-        return super().select_format(compiler, sql, params)
-
     def validate(self, value, model_instance):
         super().validate(value, model_instance)
         try: