Support forward refs

Use get_type_hints instead of the raw annotations to resolve references
within dataclasses, namedtuples and typed dicts.

Author: Zahari Kassabov

validobj/tests/test_custom.py

@@ -1,6 +1,6 @@
 import pytest
 import dataclasses
-from typing import Any
+from typing import Any, TypedDict
 
 try:
     from validobj.custom import Parser, Validator, InputType
@@ -13,7 +13,7 @@
 
 
 @pytest.mark.skipif(not HAVE_CUSTOM, reason="Custom type not found")
-def test_custom():
+def test_custom_dataclass():
     def my_float(inp: str) -> float:
         return float(inp) + 1
 
@@ -30,6 +30,23 @@ class Container:
     with pytest.raises(ValidationError):
         parse_input({"value": 5}, Container)
 
+@pytest.mark.skipif(not HAVE_CUSTOM, reason="Custom type not found")
+def test_custom_typeddict():
+    def my_float(inp: str) -> float:
+        return float(inp) + 1
+
+    MyFloat = Parser(my_float)
+    assert MyFloat.__origin__ is float
+    assert isinstance(MyFloat.__metadata__[0], InputType)
+    assert isinstance(MyFloat.__metadata__[1], Validator)
+
+    class Container(TypedDict):
+        value: MyFloat
+
+    assert parse_input({"value": "5"}, Container) == Container(value=6)
+    with pytest.raises(ValidationError):
+        parse_input({"value": 5}, Container)
+
 
 @pytest.mark.skipif(not HAVE_CUSTOM, reason="Custom type not found")
 def test_no_annotations():

validobj/tests/test_forward.py

@@ -0,0 +1,39 @@
+from typing import NamedTuple, TypedDict, Optional
+import dataclasses
+
+import validobj
+
+
+class C(TypedDict):
+    a: 'A'
+    b: 'B'
+    c: Optional['C'] = None
+
+
+class B(NamedTuple):
+    a0: 'A'
+    a1: 'A'
+
+
+@dataclasses.dataclass
+class A:
+    children: list['A']
+
+
+def test_dataclass():
+    assert validobj.parse_input({"children": [{"children": []}]}, A)
+
+
+def test_namedtuple():
+    assert validobj.parse_input([{"children": []}, {"children": []}], B)
+
+
+def test_typeddict():
+    assert validobj.parse_input(
+        {
+            'a': {'children': [{'children': []}]},
+            'b': [{"children": []}, {"children": []}],
+            'c': None,
+        },
+        C,
+    )

validobj/validation.py

@@ -10,7 +10,8 @@
 
 
 """
-from typing import Set, Union, Any, Optional, TypeVar, Type, Literal
+
+from typing import Set, Union, Any, Optional, TypeVar, Type, Literal, get_type_hints
 import sys
 
 try:
@@ -209,10 +210,18 @@ def _parse_dataclass(value, spec):
         header=f"Cannot process value into {_typename(spec)!r} because "
         f"fields do not match.",
     )
+
+    # Use this to resolve forward references.
+    annotations = get_type_hints(spec, include_extras=True)
+
     res = {}
     field_dict = {
         # Look inside InitVar
-        f.name: f.type if not isinstance(f.type, dataclasses.InitVar) else f.type.type
+        f.name: (
+            annotations[f.name]
+            if not isinstance(f.type, dataclasses.InitVar)
+            else annotations[f.name].type
+        )
         for f in fields
     }
     for k, v in value.items():
@@ -239,10 +248,12 @@ def _parse_typed_dict(value, spec):
         header=f"Cannot process value into {_typename(spec)!r} because "
         f"fields do not match.",
     )
+    # Resolve forward references.
+    annotations = get_type_hints(spec, include_extras=True)
     res = {}
     for k, v in value.items():
         try:
-            res[k] = parse_input(v, spec.__annotations__[k])
+            res[k] = parse_input(v, annotations[k])
         except ValidationError as e:
             raise WrongFieldError(
                 f"Cannot process field {k!r} of value into the "
@@ -281,10 +292,12 @@ def _parse_namedtuple(value, spec):
 
     res = {}
 
+    annotations = get_type_hints(spec, include_extras=True)
+
     for i, (k, v) in enumerate(field_inputs.items()):
-        if k in spec.__annotations__:
+        if k in annotations:
             try:
-                res[k] = parse_input(v, spec.__annotations__[k])
+                res[k] = parse_input(v, annotations[k])
             except ValidationError as e:
                 raise WrongListItemError(
                     f"Cannot process list item {i+1} into the field {k!r} of {_typename(spec)!r}",