Add basic handling of typing.Generic

Author: mciszczon

dacite/core.py

@@ -1,7 +1,7 @@
 import copy
-from dataclasses import is_dataclass
+from dataclasses import is_dataclass, dataclass
 from itertools import zip_longest
-from typing import TypeVar, Type, Optional, get_type_hints, Mapping, Any, Collection, MutableMapping
+from typing import TypeVar, Type, Optional, get_type_hints, Mapping, Any, Collection, MutableMapping, get_origin
 
 from dacite.cache import cache
 from dacite.config import Config
@@ -33,6 +33,7 @@
     is_init_var,
     extract_init_var,
     is_subclass,
+    is_generic_subclass,
 )
 
 T = TypeVar("T")
@@ -61,9 +62,10 @@ def from_dict(data_class: Type[T], data: Data, config: Optional[Config] = None)
     for field in data_class_fields:
         field = copy.copy(field)
         field.type = data_class_hints[field.name]
-        if field.name in data:
+
+        if hasattr(data, field.name) or (isinstance(data, Mapping) and field.name in data):
+            field_data = getattr(data, field.name, None) or data[field.name]
             try:
-                field_data = data[field.name]
                 value = _build_value(type_=field.type, data=field_data, config=config)
             except DaciteFieldError as error:
                 error.update_path(field.name)
@@ -98,6 +100,8 @@ def _build_value(type_: Type, data: Any, config: Config) -> Any:
         data = _build_value_for_collection(collection=type_, data=data, config=config)
     elif is_dataclass(type_) and isinstance(data, Mapping):
         data = from_dict(data_class=type_, data=data, config=config)
+    elif is_generic_subclass(type_) and is_dataclass(get_origin(type_)):
+        data = from_dict(data_class=get_origin(type_), data=data, config=config)
     for cast_type in config.cast:
         if is_subclass(type_, cast_type):
             if is_generic_collection(type_):

dacite/types.py

@@ -8,8 +8,13 @@
     TypeVar,
     Mapping,
     Tuple,
+    get_origin,
+    get_type_hints,
+    get_args,
     cast as typing_cast,
+    _GenericAlias,  # Remove import and check for Generic in a different way
 )
+from inspect import isclass
 
 from dacite.cache import cache
 
@@ -43,6 +48,16 @@ def is_generic(type_: Type) -> bool:
     return hasattr(type_, "__origin__")
 
 
+@cache
+def is_generic_subclass(type_: Type) -> bool:
+    return is_generic(type_) and hasattr(type_, "__args__")
+
+
+@cache
+def is_generic_alias(type_: Type) -> bool:
+    return type(type_.__args__) == _GenericAlias
+
+
 @cache
 def is_union(type_: Type) -> bool:
     if is_generic(type_) and type_.__origin__ == Union:
@@ -86,6 +101,22 @@ def is_init_var(type_: Type) -> bool:
     return isinstance(type_, InitVar) or type_ is InitVar
 
 
+def is_valid_generic_class(value: Any, type_: Type) -> bool:
+    if not isinstance(value, get_origin(type_)):
+        return False
+    type_hints = get_type_hints(value)
+    for field_name, field_type in type_hints.items():
+        if isinstance(field_type, TypeVar):
+            return (
+                any([isinstance(getattr(value, field_name), arg) for arg in get_args(type_)])
+                if get_args(type_)
+                else True
+            )
+        else:
+            return is_instance(value, type_)
+    return True
+
+
 @cache
 def extract_init_var(type_: Type) -> Union[Type, Any]:
     try:
@@ -128,6 +159,14 @@ def is_instance(value: Any, type_: Type) -> bool:
         return value in extract_generic(type_)
     elif is_init_var(type_):
         return is_instance(value, extract_init_var(type_))
+    elif isclass(type(type_)) and type(type_) == _GenericAlias:
+        return is_valid_generic_class(value, type_)
+    elif isinstance(type_, TypeVar):
+        if hasattr(type_, "__constraints__") and type_.__constraints__:
+            return isinstance(value, type_.__constraints__)
+        if hasattr(type_, "__bound__") and type_.__bound__:
+            return isinstance(value, type_.__bound__)
+        return True
     elif is_type_generic(type_):
         return is_subclass(value, extract_generic(type_)[0])
     else:

tests/core/test_base.py

@@ -1,9 +1,9 @@
-from dataclasses import dataclass, field
-from typing import Any, NewType, Optional
+from dataclasses import dataclass, field, asdict
+from typing import Any, NewType, Optional, TypeVar, Generic, List, Union
 
 import pytest
 
-from dacite import from_dict, MissingValueError, WrongTypeError
+from dacite import from_dict, MissingValueError, WrongTypeError, Config
 
 
 def test_from_dict_with_correct_data():
@@ -191,3 +191,67 @@ class X:
     result = from_dict(X, {"s": "test"})
 
     assert result == X(s=MyStr("test"))
+
+
+def test_from_dict_generic():
+    T = TypeVar("T", bound=Union[str, int])
+
+    @dataclass
+    class A(Generic[T]):
+        a: T
+
+    @dataclass
+    class B:
+        a_str: A[str]
+        a_int: A[int]
+
+    assert from_dict(B, {"a_str": {"a": "test"}, "a_int": {"a": 1}}) == B(a_str=A[str](a="test"), a_int=A[int](a=1))
+
+
+def test_from_dict_generic_invalid():
+    T = TypeVar("T")
+
+    @dataclass
+    class A(Generic[T]):
+        a: T
+
+    @dataclass
+    class B:
+        a_str: A[str]
+        a_int: A[int]
+
+    with pytest.raises(WrongTypeError):
+        from_dict(B, {"a_str": {"a": "test"}, "a_int": {"a": "not int"}})
+
+
+def test_from_dict_generic_common_invalid():
+    T = TypeVar("T", bound=str)
+
+    @dataclass
+    class Common(Generic[T]):
+        foo: T
+        bar: T
+
+    @dataclass
+    class A:
+        elements: List[Common[int]]
+
+    with pytest.raises(WrongTypeError):
+        from_dict(A, {"elements": [{"foo": 1, "bar": 2}, {"foo": 3, "bar": 4}]})
+
+
+def test_from_dict_generic_common():
+    T = TypeVar("T", bound=int)
+
+    @dataclass
+    class Common(Generic[T]):
+        foo: T
+        bar: T
+
+    @dataclass
+    class A:
+        elements: List[Common[int]]
+
+    result = from_dict(A, {"elements": [{"foo": 1, "bar": 2}, {"foo": 3, "bar": 4}]})
+
+    assert result == A(elements=[Common[int](1, 2), Common[int](3, 4)])

tests/test_types.py

@@ -1,4 +1,4 @@
-from dataclasses import InitVar
+from dataclasses import InitVar, dataclass
 from typing import Optional, Union, List, Any, Dict, NewType, TypeVar, Generic, Collection, Tuple, Type
 from unittest.mock import patch, Mock
 
@@ -268,13 +268,13 @@ def test_is_instance_with_with_type_and_not_matching_value_type():
     assert not is_instance(1, Type[str])
 
 
-def test_is_instance_with_not_supported_generic_types():
+def test_is_instance_with_generic_types():
     T = TypeVar("T")
 
     class X(Generic[T]):
         pass
 
-    assert not is_instance(X[str](), X[str])
+    assert is_instance(X[str](), X[str])
 
 
 def test_is_instance_with_generic_mapping_and_matching_value_type():
@@ -364,6 +364,10 @@ def test_is_instance_with_empty_tuple_and_not_matching_type():
     assert not is_instance((1, 2), Tuple[()])
 
 
+def test_is_instance_list_type():
+    assert is_instance([{}], List)
+
+
 def test_extract_generic():
     assert extract_generic(List[int]) == (int,)