Serialization bug when using schema inheritance

[cristianmatache]

Describe the bug

dataclasses-avroschema/dataclasses_avroschema/utils.py

Lines 126 to 127 in ed935bb

	if is_union(model.__annotations__[field_name]) and include_type:
	asdict["-type"] = value.get_fullname()

In this code section .__annotations__ is misused. __annotations__ is accessed on the instance, which has the same behavior as accessing it on the class (type(instance)). In this case, __annotations__ only contains the fields of the current class but not those of its parent classes.

To Reproduce

from dataclasses import dataclass

from dataclasses_avroschema import AvroModel

@dataclass
class A(AvroModel):
    a: int

@dataclass
class Parent(AvroModel):
    p: A

@dataclass
class Child(Parent):
    c: int

child = Child(p=A(1), c=1)
child.serialize()  # Errors

Further notes on __annotations__:

assert Child.__annotations__ == child.__annotations__ == {'c': int}
from typing import get_type_hints
assert set(get_type_hints(child)) == {'c'}  # On the instance
assert {'p', 'c'}.issubset(set(get_type_hints(Child)))  # On the class

Expected behavior
Serialization should succeed.

Suggestions

• Use typing.get_type_hints
• Make it more performant by adding an lru_cache for example

%timeit is_union(get_type_hints(type(model))[field_name])
41.1 µs ± 819 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)


from functools import lru_cache
@lru_cache
def f(model_t, field_name):
    return is_union(get_type_hints(model_t)[field_name])

%timeit f(type(model), field_name)
160 ns ± 3.13 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

[marcosschroh]

Thanks for reporting it. I am a bit busy but as soon as I have time I will take a look

[marcosschroh]

Fixed in the next released

[cristianmatache]

Thank you, @marcosschroh!

I have 2 questions, out of curiosity

• why not use @lru_cache, the whole serialization would become much more performant?
• why do we need this as "a hack"

  dataclasses-avroschema/dataclasses_avroschema/utils.py

  Lines 132 to 136 in f5ca713

  	annotations = model.__annotations__
  	# This is a hack to get the annotations from the parent class
  	# https://github.com/marcosschroh/dataclasses-avroschema/issues/800
  	if model.__class__.mro()[1] != base_class:
  	annotations.update(typing.get_type_hints(model.__class__))

  ?