Support manually mapped (e.g. reflected) tables

Mapped tables must not always be sub classes of DeclarativeBase.

Author: Cito

graphene_sqlalchemy/tests/models.py

@@ -2,7 +2,7 @@
 
 from sqlalchemy import Column, Date, ForeignKey, Integer, String, Table
 from sqlalchemy.ext.declarative import declarative_base
-from sqlalchemy.orm import relationship
+from sqlalchemy.orm import mapper, relationship
 
 Base = declarative_base()
 
@@ -41,3 +41,11 @@ class Article(Base):
     headline = Column(String(100))
     pub_date = Column(Date())
     reporter_id = Column(Integer(), ForeignKey('reporters.id'))
+
+
+class ReflectedEditor:
+    """Same as Editor, but using reflected table."""
+
+editor_table = Table('editors', Base.metadata, autoload=True)
+
+mapper(ReflectedEditor, editor_table)

graphene_sqlalchemy/tests/test_reflected.py

@@ -0,0 +1,24 @@
+
+from graphene import ObjectType
+
+from ..registry import Registry
+from ..types import SQLAlchemyObjectType
+from .models import ReflectedEditor
+
+registry = Registry()
+
+
+class Reflected(SQLAlchemyObjectType):
+
+    class Meta:
+        model = ReflectedEditor
+        registry = registry
+
+
+def test_objecttype_registered():
+    assert issubclass(Reflected, ObjectType)
+    assert Reflected._meta.model == ReflectedEditor
+    assert list(
+        Reflected._meta.fields.keys()) == ['editor_id', 'name']
+
+

graphene_sqlalchemy/types.py

@@ -15,7 +15,7 @@
                         convert_sqlalchemy_composite,
                         convert_sqlalchemy_relationship)
 from .registry import Registry, get_global_registry
-from .utils import get_query, is_mapped
+from .utils import get_query, is_mapped_class, is_mapped_instance
 
 
 def construct_fields(options):
@@ -91,7 +91,7 @@ def __new__(cls, name, bases, attrs):
             'The attribute registry in {}.Meta needs to be an'
             ' instance of Registry, received "{}".'
         ).format(name, options.registry)
-        assert is_mapped(options.model), (
+        assert is_mapped_class(options.model), (
             'You need to pass a valid SQLAlchemy Model in '
             '{}.Meta, received "{}".'
         ).format(name, options.model)
@@ -120,7 +120,7 @@ class SQLAlchemyObjectType(six.with_metaclass(SQLAlchemyObjectTypeMeta, ObjectTy
     def is_type_of(cls, root, context, info):
         if isinstance(root, cls):
             return True
-        if not is_mapped(type(root)):
+        if not is_mapped_instance(root):
             raise Exception((
                 'Received incompatible instance "{}".'
             ).format(root))

graphene_sqlalchemy/utils.py

@@ -1,4 +1,6 @@
-from sqlalchemy.ext.declarative.api import DeclarativeMeta
+from sqlalchemy.exc import ArgumentError
+from sqlalchemy.orm import class_mapper, object_mapper
+from sqlalchemy.orm.exc import UnmappedClassError, UnmappedInstanceError
 
 
 def get_session(context):
@@ -16,5 +18,19 @@ def get_query(model, context):
     return query
 
 
-def is_mapped(obj):
-    return isinstance(obj, DeclarativeMeta)
+def is_mapped_class(cls):
+    try:
+        class_mapper(cls)
+    except (ArgumentError, UnmappedClassError):
+        return False
+    else:
+        return True
+
+
+def is_mapped_instance(cls):
+    try:
+        object_mapper(cls)
+    except (ArgumentError, UnmappedInstanceError):
+        return False
+    else:
+        return True