Fix select_related empty result handling

sqlalchemy_json_api/query_builder.py

@@ -201,7 +201,22 @@ def _select_related(self, obj, relationship_key, **kwargs):
         from_obj = kwargs.pop('from_obj', None)
         if from_obj is None:
             from_obj = sa.orm.query.Query(model)
-        from_obj = from_obj.filter(prop._with_parent(obj))
+
+        # SQLAlchemy Query.with_parent throws warning if the primary object
+        # foreign key is NULL. Thus we need this ugly magic to return empty
+        # data in that scenario.
+        if (
+            prop.direction.name == 'MANYTOONE' and
+            not prop.secondary and
+            getattr(obj, prop.local_remote_pairs[0][0].key) is None
+        ):
+            expr = sa.cast({'data': None}, JSONB)
+            if kwargs.get('as_text'):
+                expr = sa.cast(expr, sa.Text)
+            return sa.select([expr])
+
+        from_obj = from_obj.with_parent(obj, prop)
+
         if prop.order_by:
             from_obj = from_obj.order_by(*prop.order_by)
 
@@ -267,7 +282,18 @@ def select(self, model, **kwargs):
         if from_obj is None:
             from_obj = sa.orm.query.Query(model)
 
-        from_obj = from_obj.subquery()
+        if kwargs.get('sort') is not None:
+            from_obj = apply_sort(
+                from_obj.statement,
+                from_obj,
+                kwargs.get('sort')
+            )
+        if kwargs.get('limit') is not None:
+            from_obj = from_obj.limit(kwargs.get('limit'))
+        if kwargs.get('offset') is not None:
+            from_obj = from_obj.offset(kwargs.get('offset'))
+
+        from_obj = from_obj.cte('main_query')
 
         return SelectExpression(self, model, from_obj).build_select(**kwargs)
 
@@ -404,17 +430,11 @@ def _get_from_args(
         from_args = [data_query.as_scalar().label('data')]
 
         if params.include:
-            selectable = get_selectable(self.from_obj).original
-            if params.sort is not None:
-                selectable = apply_sort(selectable, selectable, params.sort)
-            if params.limit is not None:
-                selectable = selectable.limit(params.limit)
-            if params.offset is not None:
-                selectable = selectable.offset(params.offset)
+            selectable = self.from_obj
             include_expr = IncludeExpression(
                 self.query_builder,
                 self.model,
-                selectable.alias()
+                selectable
             )
             included_query = include_expr.build_included(params)
             from_args.append(included_query.as_scalar().label('included'))
@@ -717,12 +737,6 @@ def build_data_expr(self, params, ids_only=False):
     def build_data(self, params, ids_only=False):
         expr = self.build_data_expr(params, ids_only=ids_only)
         query = sa.select([expr], from_obj=self.from_obj)
-        if params.sort is not None:
-            query = apply_sort(self.from_obj, query, params.sort)
-        if params.limit is not None:
-            query = query.limit(params.limit)
-        if params.offset is not None:
-            query = query.offset(params.offset)
         return query
 
     def build_data_array(self, params, ids_only=False):
@@ -797,7 +811,7 @@ def build_single_included(self, fields, path):
             expr,
             path,
             alias,
-            get_selectable(self.from_obj),
+            self.from_obj,
             correlate=False
         ).distinct()
         if cls is self.model:

tests/conftest.py

@@ -1,3 +1,5 @@
+import warnings
+
 import pytest
 import sqlalchemy as sa
 from sqlalchemy import create_engine
@@ -7,6 +9,8 @@
 
 from sqlalchemy_json_api import QueryBuilder
 
+warnings.filterwarnings('error')
+
 
 @pytest.fixture(scope='class')
 def base():
@@ -231,7 +235,7 @@ class CompositePKModel(base):
 
 @pytest.fixture(scope='class')
 def dns():
-    return 'postgres://postgres@localhost/sqlalchemy_json_api_test'
+    return 'postgresql://postgres@localhost/sqlalchemy_json_api_test'
 
 
 @pytest.yield_fixture(scope='class')

tests/test_select.py

@@ -459,7 +459,7 @@ def test_hybrid_property_inclusion_uses_clause_adaptation(
             from_obj=session.query(article_cls)
         )
         compiled = query.compile(dialect=sa.dialects.postgresql.dialect())
-        assert 'upper(anon_2.name)' in str(compiled)
+        assert 'upper(main_query.name)' in str(compiled)
 
     @pytest.mark.parametrize(
         ('fields', 'include', 'result'),

tests/test_select_related.py

@@ -296,6 +296,33 @@ def test_empty_result(
         query = query_builder.select_related(
             session.query(category_cls).get(id),
             'parent',
-            fields={'categories': []}
+            fields={'categories': []},
+            session=session
         )
         assert session.execute(query).scalar() == result
+
+    @pytest.mark.parametrize(
+        ('id', 'result'),
+        (
+            (
+                1,
+                {'data': None}
+            ),
+        )
+    )
+    def test_empty_result_as_text(
+        self,
+        query_builder,
+        session,
+        category_cls,
+        id,
+        result
+    ):
+        query = query_builder.select_related(
+            session.query(category_cls).get(id),
+            'parent',
+            fields={'categories': []},
+            session=session,
+            as_text=True
+        )
+        assert json.loads(session.execute(query).scalar()) == result

tests/test_select_with_include.py

@@ -668,8 +668,37 @@ def test_hybrid_property_in_included_object(
                 category_cls.id == 1
             )
         )
-        from pprint import pprint
-        pprint(session.execute(query).scalar())
+        assert session.execute(query).scalar() == {
+            'included': [
+                {
+                    'attributes': {'comment_count': 4},
+                    'type': 'articles',
+                    'id': '1'
+                }
+            ],
+            'data': [
+                {
+                    'relationships': {
+                        'articles': {
+                            'data': [{'type': 'articles', 'id': '1'}]
+                        },
+                        'subcategories': {
+                            'data': [
+                                {'type': 'categories', 'id': '2'},
+                                {'type': 'categories', 'id': '4'}
+                            ]
+                        },
+                        'parent': {'data': None}
+                    },
+                    'attributes': {
+                        'created_at': None,
+                        'name': 'Some category'
+                    },
+                    'type': 'categories',
+                    'id': '1'
+                }
+            ]
+        }
 
     @pytest.mark.parametrize(
         ('fields', 'include', 'result'),