Added mypy static checking

.gitignore

@@ -80,3 +80,4 @@ target/
 # Databases
 *.sqlite3
 .vscode
+.mypy_cache

.travis.yml

@@ -27,12 +27,19 @@ install:
   elif [ "$TEST_TYPE" = lint ]; then
     pip install flake8
   fi
+  elif [ "$TEST_TYPE" = mypy ]; then
+    pip install mypy
+  fi
 script:
 - |
   if [ "$TEST_TYPE" = lint ]; then
     echo "Checking Python code lint."
     flake8 graphene
     exit
+  elif [ "$TEST_TYPE" = mypy ]; then
+    echo "Checking Python types."
+    mypy graphene
+    exit
   elif [ "$TEST_TYPE" = build ]; then
     py.test --cov=graphene graphene examples
   fi
@@ -51,6 +58,8 @@ matrix:
   include:
   - python: '2.7'
     env: TEST_TYPE=lint
+  - python: '3.6'
+    env: TEST_TYPE=mypy
 deploy:
   provider: pypi
   user: syrusakbary

graphene/pyutils/init_subclass.py

@@ -16,4 +16,4 @@ if not is_init_subclass_available:
             if hasattr(super_class, '__init_subclass__'):
                 super_class.__init_subclass__.__func__(cls, **kwargs)
 else:
-    InitSubclassMeta = type
+    InitSubclassMeta = type  # type: ignore

graphene/types/inputobjecttype.py

@@ -6,8 +6,14 @@ from .unmountedtype import UnmountedType
 from .utils import yank_fields_from_attrs
 
 
+# For static type checking with Mypy
+MYPY = False
+if MYPY:
+    from typing import Dict, Callable
+
+
 class InputObjectTypeOptions(BaseOptions):
-    fields = None  # type: Dict[str, Field]
+    fields = None  # type: Dict[str, InputField]
     create_container = None  # type: Callable
 
 

graphene/types/interface.py

@@ -4,6 +4,11 @@ from .base import BaseOptions, BaseType
 from .field import Field
 from .utils import yank_fields_from_attrs
 
+# For static type checking with Mypy
+MYPY = False
+if MYPY:
+    from typing import Dict
+
 
 class InterfaceOptions(BaseOptions):
     fields = None  # type: Dict[str, Field]

graphene/types/mutation.py

@@ -8,10 +8,17 @@ from .utils import yank_fields_from_attrs
 from ..utils.deprecated import warn_deprecation
 
 
+# For static type checking with Mypy
+MYPY = False
+if MYPY:
+    from .argument import Argument
+    from typing import Dict, Type, Callable
+
+
 class MutationOptions(ObjectTypeOptions):
     arguments = None  # type: Dict[str, Argument]
     output = None  # type: Type[ObjectType]
-    resolver = None  # type: Function
+    resolver = None  # type: Callable
 
 
 class Mutation(ObjectType):

graphene/types/objecttype.py

@@ -5,10 +5,15 @@ from .field import Field
 from .interface import Interface
 from .utils import yank_fields_from_attrs
 
+# For static type checking with Mypy
+MYPY = False
+if MYPY:
+    from typing import Dict, Iterable, Type
+
 
 class ObjectTypeOptions(BaseOptions):
     fields = None  # type: Dict[str, Field]
-    interfaces = ()  # type: List[Type[Interface]]
+    interfaces = ()  # type: Iterable[Type[Interface]]
 
 
 class ObjectType(BaseType):

graphene/types/scalars.py

@@ -86,6 +86,7 @@ class Float(Scalar):
 
     @staticmethod
     def coerce_float(value):
+        # type: (Any) -> float
         try:
             return float(value)
         except ValueError:

graphene/types/union.py

@@ -2,8 +2,15 @@ from .base import BaseOptions, BaseType
 from .unmountedtype import UnmountedType
 
 
+# For static type checking with Mypy
+MYPY = False
+if MYPY:
+    from .objecttype import ObjectType
+    from typing import Iterable, Type
+
+
 class UnionOptions(BaseOptions):
-    types = ()  # type: List[Type[ObjectType]]
+    types = ()  # type: Iterable[Type[ObjectType]]
 
 
 class Union(UnmountedType, BaseType):

mypy.ini

@@ -0,0 +1,17 @@
+[mypy]
+ignore_missing_imports = True
+
+[mypy-graphene.pyutils.*]
+ignore_errors = True
+
+[mypy-graphene.types.scalars]
+ignore_errors = True
+
+[mypy-graphene.types.generic]
+ignore_errors = True
+
+[mypy-graphene.types.tests.*]
+ignore_errors = True
+
+[mypy-graphene.relay.tests.*]
+ignore_errors = True