Merge pull request #584 from yukinarit/fix-init-var-field-attribute

Fix InitVar with field attribute

serde/core.py

@@ -890,15 +890,25 @@ def should_impl_dataclass(cls: type[Any]) -> bool:
     if not dataclasses.is_dataclass(cls):
         return True
 
+    # Checking is_dataclass is not enough in such a case that the class is inherited
+    # from another dataclass. To do it correctly, check if all fields in __annotations__
+    # are present as dataclass fields.
     annotations = getattr(cls, "__annotations__", {})
     if not annotations:
         return False
 
     field_names = [field.name for field in dataclass_fields(cls)]
-    for field_name in annotations:
+    for field_name, annotation in annotations.items():
+        # Omit InitVar field because it doesn't appear in dataclass fields.
+        if is_instance(annotation, dataclasses.InitVar):
+            continue
+        # This field in __annotations__ is not a part of dataclass fields.
+        # This means this class does not implement dataclass directly.
         if field_name not in field_names:
             return True
 
+    # If all of the fields in __annotation__ are present as dataclass fields,
+    # the class already implemented dataclass, thus returns False.
     return False
 
 

tests/test_basics.py

@@ -1126,3 +1126,12 @@ class Bar(Foo):
 
     bar = Bar(a=10, b=20)
     assert bar == serde.from_dict(Bar, serde.to_dict(bar))
+
+
+def test_init_var_with_field_attribute() -> None:
+    @serde.serde
+    @dataclasses.dataclass
+    class Foo:
+        a: int = serde.field(skip=True)
+
+    assert serde.to_dict(Foo(10)) == {}