Support type hints for specifying property types

README.rst

@@ -154,6 +154,49 @@ Example
     }
 
 
+Type Hinting
+------------
+
+You can also specify types for properties with Type Hinting, if available:
+
+.. code-block:: python
+
+    >>> from json import dumps
+    >>> from typing import List
+    >>> from jsonobject import Property, PropertySet, EnumProperty
+
+    >>> class Wheel(PropertySet):
+    ...    diameter: float = Property(default=1.)
+
+    >>> class Rating(EnumProperty):
+    ...    ok = 'ok'
+    ...    bad = 'bad'
+    ...    good = 'good'
+
+    >>> class Car(PropertySet):
+    ...    wheels: List[Wheel] = Property()
+    ...    brand = Property()
+    ...    model = Property()
+    ...    rating: Rating = Property(default=Rating.ok)
+
+    >>> volvo = Car(brand='Volvo', model='V90', rating=Rating.good, wheels=[])
+    >>> volvo.wheels.append(Wheel(diameter=3.))
+    >>> print(volvo.to_json())
+    {
+      "*schema": "Car",
+      "brand": "Volvo",
+      "model": "V90",
+      "rating": "good",
+      "wheels": [
+        {
+          "*schema": "Wheel",
+          "diameter": 3.0
+        }
+      ]
+    }
+
+
+
 Schema-Less
 -----------
 

jsonobject/types.py

@@ -1,5 +1,12 @@
 import json
 import urllib
+
+try:
+    import typing
+    has_typing = True
+except ImportError:
+    has_typing = False
+
 from enum import Enum
 from .schema import wrap_dict, wrap_raw_json
 
@@ -9,14 +16,7 @@ def __init__(self, type=str, name=None, default=None, enum=None,
                  required=False, validator=None, wrap=False, none=None,
                  is_list=False, calculated=False):
 
-        if type not in (str, int, float, bool) or is_list:
-            if default is not None:
-                raise ValueError('Can only use default values for simple types')
-            elif none is not None:
-                raise ValueError('None value only makes sense for simple types')
-
-        if is_list and not issubclass(type, PropertySet):
-            raise ValueError('Please use is_list only with ProperySet')
+        self._check_type(type, is_list, default, none)
 
         self.serialized_name = name
         self.type = enum if enum else type
@@ -30,12 +30,43 @@ def __init__(self, type=str, name=None, default=None, enum=None,
         self._property_name = None
         self.calculated = calculated
 
+    @staticmethod
+    def _check_type(type, is_list, default, none):
+        if type not in (str, int, float, bool) or is_list:
+            if default is not None:
+                raise ValueError('Can only use default values for simple types')
+            elif none is not None:
+                raise ValueError('None value only makes sense for simple types')
+
+        if is_list and not issubclass(type, PropertySet):
+            raise ValueError('Please use is_list only with ProperySet')
+
     def __property_config__(self, model_class, property_name):
         self.model_class = model_class
         self._property_name = property_name
         if self.serialized_name is None:
             self.serialized_name = property_name
 
+        if has_typing and hasattr(model_class, '__annotations__'):
+            annotation = model_class.__annotations__.get(property_name)
+            if annotation is not None:
+                if issubclass(annotation, typing.List):
+                    is_list = True
+                    if len(annotation.__args__) != 1:
+                        raise ValueError('List annotations must be typed')
+                    type = annotation.__args__[0]
+                elif issubclass(annotation, EnumProperty):
+                    is_list = False
+                    type = str
+                    self.enum = annotation
+                else:
+                    is_list = False
+                    type = annotation
+
+                self._check_type(type, is_list, self.default, self.none)
+                self.is_list = is_list
+                self.type = type
+
     def __get__(self, model_instance, model_class):
         if model_instance is None:
             return self

setup.cfg

@@ -2,6 +2,7 @@
 norecursedirs = .git .cache scripts build dist conda-recipe benchmarks __pycache__ doc
 pep8ignore =
     doc/conf.py ALL
+    tests/*.py E701
 pep8maxlinelength = 119
 flakes-ignore =
     __init__.py UnusedImport

tests/test_booleans.py

@@ -153,3 +153,12 @@ class O(PropertySet):
     del o.s
 
     assert o.s is None
+
+
+def test_type_via_hint():
+    class O(PropertySet):
+        s: bool = Property()
+
+    o = O(s='yes')
+
+    assert type(o.s) is bool

tests/test_dicts.py

@@ -109,3 +109,12 @@ class O(PropertySet):
     o = O()
 
     assert type(o.s) is dict
+
+
+def test_via_hint():
+    class O(PropertySet):
+        s: dict = Property()
+
+    o = O()
+
+    assert type(o.s) is dict

tests/test_is_list.py

@@ -2,6 +2,7 @@
 
 import pytest
 from jsonobject import PropertySet, Property
+from typing import List
 
 
 def test_list_of_property_sets():
@@ -165,3 +166,20 @@ class P(PropertySet):
     with pytest.raises(ValueError):
         class O(PropertySet):
             s = Property(P, is_list=True, default=1)
+
+
+def test_list_via_hint():
+    class P(PropertySet):
+        s: str = Property()
+
+    class O(PropertySet):
+        s: List[P] = Property()
+
+    p1 = P()
+    p2 = P()
+    p3 = P()
+    o = O(s=[p1, p2, p3])
+
+    assert len(o.s) == 3
+    assert o.s == [p1, p2, p3]
+    assert o.to_dict() == O(o.to_dict()).to_dict()

tests/test_numbers.py

@@ -13,6 +13,15 @@ class O(PropertySet):
     assert o.s == 1
 
 
+def test_type_hint_set_via_constructor():
+    class O(PropertySet):
+        s: int = Property()
+
+    o = O(s=1)
+
+    assert o.s == 1
+
+
 def test_set_via_attribute():
     class O(PropertySet):
         s = Property(int)
@@ -23,6 +32,16 @@ class O(PropertySet):
     assert o.s == 1
 
 
+def test_type_hint_set_via_attribute():
+    class O(PropertySet):
+        s: int = Property()
+
+    o = O()
+    o.s = 1
+
+    assert o.s == 1
+
+
 def test_set_default():
     class O(PropertySet):
         s = Property(int, default=1)

tests/test_strings.py

@@ -13,6 +13,15 @@ class O(PropertySet):
     assert o.s == 'test'
 
 
+def test_type_hint_set_via_constructor():
+    class O(PropertySet):
+        s: str = Property()
+
+    o = O(s='test')
+
+    assert o.s == 'test'
+
+
 def test_set_via_attribute():
     class O(PropertySet):
         s = Property()