Fix non-generic protocols (#436)

* Fix non-generic protocols

* Fix generics on 3.8

Author: Tinche

HISTORY.md

@@ -50,6 +50,8 @@
 - _cattrs_ is now linted with [Ruff](https://beta.ruff.rs/docs/).
 - Remove some unused lines in the unstructuring code.
   ([#416](https://github.com/python-attrs/cattrs/pull/416))
+- Fix handling classes inheriting from non-generic protocols.
+  ([#374](https://github.com/python-attrs/cattrs/issues/374))
 
 ## 23.1.2 (2023-06-02)
 

Makefile

@@ -49,6 +49,7 @@ clean-test: ## remove test and coverage artifacts
 
 lint: ## check style with ruff and black
 	pdm run ruff src/ tests
+	pdm run isort -c src/ tests
 	pdm run black --check src tests docs/conf.py
 
 test: ## run tests quickly with the default Python

src/cattrs/_compat.py

@@ -316,8 +316,11 @@ def is_counter(type):
         )
 
     def is_generic(obj) -> bool:
-        return isinstance(obj, (_GenericAlias, GenericAlias)) or is_subclass(
-            obj, Generic
+        """Whether obj is a generic type."""
+        # Inheriting from protocol will inject `Generic` into the MRO
+        # without `__orig_bases__`.
+        return isinstance(obj, (_GenericAlias, GenericAlias)) or (
+            is_subclass(obj, Generic) and hasattr(obj, "__orig_bases__")
         )
 
     def copy_with(type, args):
@@ -343,7 +346,7 @@ def get_full_type_hints(obj, globalns=None, localns=None):
     TupleSubscriptable = Tuple
 
     from collections import Counter as ColCounter
-    from typing import Counter, TypedDict, Union, _GenericAlias
+    from typing import Counter, Generic, TypedDict, Union, _GenericAlias
 
     from typing_extensions import Annotated, NotRequired, Required
     from typing_extensions import get_origin as te_get_origin
@@ -429,7 +432,9 @@ def is_literal(type) -> bool:
         return type.__class__ is _GenericAlias and type.__origin__ is Literal
 
     def is_generic(obj):
-        return isinstance(obj, _GenericAlias)
+        return isinstance(obj, _GenericAlias) or (
+            is_subclass(obj, Generic) and hasattr(obj, "__orig_bases__")
+        )
 
     def copy_with(type, args):
         """Replace a generic type's arguments."""

src/cattrs/preconf/orjson.py

@@ -1,6 +1,6 @@
 """Preconfigured converters for orjson."""
 from base64 import b85decode, b85encode
-from datetime import datetime, date
+from datetime import date, datetime
 from enum import Enum
 from typing import Any, Type, TypeVar, Union
 

tests/test_baseconverter.py

@@ -1,9 +1,8 @@
 """Test both structuring and unstructuring."""
 from typing import Optional, Union
 
-import attr
 import pytest
-from attr import define, fields, make_class
+from attrs import define, fields, make_class
 from hypothesis import HealthCheck, assume, given, settings
 from hypothesis.strategies import just, one_of
 
@@ -90,9 +89,9 @@ def test_union_field_roundtrip(cl_and_vals_a, cl_and_vals_b, strat):
     common_names = a_field_names & b_field_names
     assume(len(a_field_names) > len(common_names))
 
-    @attr.s
+    @define
     class C:
-        a = attr.ib(type=Union[cl_a, cl_b])
+        a: Union[cl_a, cl_b]
 
     inst = C(a=cl_a(*vals_a, **kwargs_a))
 
@@ -161,9 +160,9 @@ def test_optional_field_roundtrip(cl_and_vals):
     converter = BaseConverter()
     cl, vals, kwargs = cl_and_vals
 
-    @attr.s
+    @define
     class C:
-        a = attr.ib(type=Optional[cl])
+        a: Optional[cl]
 
     inst = C(a=cl(*vals, **kwargs))
     assert inst == converter.structure(converter.unstructure(inst), C)

tests/test_gen.py

@@ -2,7 +2,7 @@
 import linecache
 from traceback import format_exc
 
-from attr import define
+from attrs import define
 
 from cattrs import Converter
 from cattrs.gen import make_dict_structure_fn, make_dict_unstructure_fn

tests/test_generics.py

@@ -2,7 +2,7 @@
 from typing import Deque, Dict, Generic, List, Optional, TypeVar, Union
 
 import pytest
-from attr import asdict, attrs, define
+from attrs import asdict, define
 
 from cattrs import BaseConverter, Converter
 from cattrs._compat import Protocol
@@ -132,7 +132,7 @@ def test_able_to_structure_deeply_nested_generics_gen(converter):
 
 
 def test_structure_unions_of_generics(converter):
-    @attrs(auto_attribs=True)
+    @define
     class TClass2(Generic[T]):
         c: T
 
@@ -142,7 +142,7 @@ class TClass2(Generic[T]):
 
 
 def test_structure_list_of_generic_unions(converter):
-    @attrs(auto_attribs=True)
+    @define
     class TClass2(Generic[T]):
         c: T
 
@@ -154,7 +154,7 @@ class TClass2(Generic[T]):
 
 
 def test_structure_deque_of_generic_unions(converter):
-    @attrs(auto_attribs=True)
+    @define
     class TClass2(Generic[T]):
         c: T
 
@@ -179,35 +179,31 @@ def test_raises_if_no_generic_params_supplied(
     assert exc.value.type_ is T
 
 
-def test_unstructure_generic_attrs():
-    c = Converter()
-
-    @attrs(auto_attribs=True)
+def test_unstructure_generic_attrs(genconverter):
+    @define
     class Inner(Generic[T]):
         a: T
 
-    @attrs(auto_attribs=True)
+    @define
     class Outer:
         inner: Inner[int]
 
     initial = Outer(Inner(1))
-    raw = c.unstructure(initial)
+    raw = genconverter.unstructure(initial)
 
     assert raw == {"inner": {"a": 1}}
 
-    new = c.structure(raw, Outer)
+    new = genconverter.structure(raw, Outer)
     assert initial == new
 
-    @attrs(auto_attribs=True)
+    @define
     class OuterStr:
         inner: Inner[str]
 
-    assert c.structure(raw, OuterStr) == OuterStr(Inner("1"))
-
+    assert genconverter.structure(raw, OuterStr) == OuterStr(Inner("1"))
 
-def test_unstructure_deeply_nested_generics():
-    c = Converter()
 
+def test_unstructure_deeply_nested_generics(genconverter):
     @define
     class Inner:
         a: int
@@ -217,16 +213,14 @@ class Outer(Generic[T]):
         inner: T
 
     initial = Outer[Inner](Inner(1))
-    raw = c.unstructure(initial, Outer[Inner])
+    raw = genconverter.unstructure(initial, Outer[Inner])
     assert raw == {"inner": {"a": 1}}
 
-    raw = c.unstructure(initial)
+    raw = genconverter.unstructure(initial)
     assert raw == {"inner": {"a": 1}}
 
 
-def test_unstructure_deeply_nested_generics_list():
-    c = Converter()
-
+def test_unstructure_deeply_nested_generics_list(genconverter):
     @define
     class Inner:
         a: int
@@ -236,16 +230,14 @@ class Outer(Generic[T]):
         inner: List[T]
 
     initial = Outer[Inner]([Inner(1)])
-    raw = c.unstructure(initial, Outer[Inner])
+    raw = genconverter.unstructure(initial, Outer[Inner])
     assert raw == {"inner": [{"a": 1}]}
 
-    raw = c.unstructure(initial)
+    raw = genconverter.unstructure(initial)
     assert raw == {"inner": [{"a": 1}]}
 
 
-def test_unstructure_protocol():
-    c = Converter()
-
+def test_unstructure_protocol(genconverter):
     class Proto(Protocol):
         a: int
 
@@ -258,10 +250,10 @@ class Outer:
         inner: Proto
 
     initial = Outer(Inner(1))
-    raw = c.unstructure(initial, Outer)
+    raw = genconverter.unstructure(initial, Outer)
     assert raw == {"inner": {"a": 1}}
 
-    raw = c.unstructure(initial)
+    raw = genconverter.unstructure(initial)
     assert raw == {"inner": {"a": 1}}
 
 
@@ -306,3 +298,27 @@ class B(A[int]):
         pass
 
     assert generate_mapping(B, {}) == {T.__name__: int}
+
+
+def test_nongeneric_protocols(converter):
+    """Non-generic protocols work."""
+
+    class NongenericProtocol(Protocol):
+        ...
+
+    @define
+    class Entity(NongenericProtocol):
+        ...
+
+    assert generate_mapping(Entity) == {}
+
+    class GenericProtocol(Protocol[T]):
+        ...
+
+    @define
+    class GenericEntity(GenericProtocol[int]):
+        a: int
+
+    assert generate_mapping(GenericEntity) == {"T": int}
+
+    assert converter.structure({"a": 1}, GenericEntity) == GenericEntity(1)

tests/test_validation.py

@@ -1,8 +1,8 @@
 """Tests for the extended validation mode."""
+import pickle
 from typing import Dict, FrozenSet, List, Set, Tuple
 
 import pytest
-import pickle
 from attrs import define, field
 from attrs.validators import in_
 from hypothesis import given