From 7cfec55410d71adc6790634532f5142f4bc1107f Mon Sep 17 00:00:00 2001
From: Syrus Akbary <me@syrusakbary.com>
Date: Mon, 7 Aug 2017 20:48:20 -0700
Subject: [PATCH] Added mypy static checking

---
 .gitignore                        |  1 +
 .travis.yml                       |  9 +++++++++
 graphene/pyutils/init_subclass.py |  2 +-
 graphene/types/inputobjecttype.py |  8 +++++++-
 graphene/types/interface.py       |  5 +++++
 graphene/types/mutation.py        |  9 ++++++++-
 graphene/types/objecttype.py      |  7 ++++++-
 graphene/types/scalars.py         |  1 +
 graphene/types/union.py           |  9 ++++++++-
 mypy.ini                          | 17 +++++++++++++++++
 10 files changed, 63 insertions(+), 5 deletions(-)
 create mode 100644 mypy.ini

diff --git a/.gitignore b/.gitignore
index 9f465556..d98ebfc3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -80,3 +80,4 @@ target/
 # Databases
 *.sqlite3
 .vscode
+.mypy_cache
diff --git a/.travis.yml b/.travis.yml
index 239df23d..e5d52a0a 100644
--- a/.travis.yml
+++ b/.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
diff --git a/graphene/pyutils/init_subclass.py b/graphene/pyutils/init_subclass.py
index c3a6143c..78e4ff19 100644
--- a/graphene/pyutils/init_subclass.py
+++ b/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
diff --git a/graphene/types/inputobjecttype.py b/graphene/types/inputobjecttype.py
index 3beb3ebf..28dc220b 100644
--- a/graphene/types/inputobjecttype.py
+++ b/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
 
 
diff --git a/graphene/types/interface.py b/graphene/types/interface.py
index c98f0f1f..b806de33 100644
--- a/graphene/types/interface.py
+++ b/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]
diff --git a/graphene/types/mutation.py b/graphene/types/mutation.py
index 213c0f48..6a7a7bbb 100644
--- a/graphene/types/mutation.py
+++ b/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):
diff --git a/graphene/types/objecttype.py b/graphene/types/objecttype.py
index c579a88e..53e00902 100644
--- a/graphene/types/objecttype.py
+++ b/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):
diff --git a/graphene/types/scalars.py b/graphene/types/scalars.py
index ccfb089c..3b78185d 100644
--- a/graphene/types/scalars.py
+++ b/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:
diff --git a/graphene/types/union.py b/graphene/types/union.py
index f9797fc0..ae6af8b4 100644
--- a/graphene/types/union.py
+++ b/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):
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
index 00000000..bbb37b77
--- /dev/null
+++ b/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