Dialect does not work with inheritance

[QSHolzner]

• mashumaro version: 3.0.1
• Python version: 3.10
• Operating System: Linux

Description

If more classes share the same base class the to_dict and from_dict functions get only generated for the class which first called to_dict or from dict. This is because all classes use the __dialect_to_dict_cache__ attribute from the base class. So the first execution of to_dict generates the function and put it into the __dialect_to_dict_cache__ from the base class. Every call of to_dict in a different class uses the fuction from the cache.

What I Did

In the following example the call entity2.to_dict() raises an exception because the to_dict function from Entity1 is used.
This can be seen by the function adress in the __dialect_to_dict_cache__ Dictionary.

from dataclasses import dataclass
from datetime import date, datetime

from mashumaro import DataClassDictMixin
from mashumaro.config import ADD_DIALECT_SUPPORT
from mashumaro.dialect import Dialect
from mashumaro.types import SerializationStrategy


class DateTimeSerializationStrategy(SerializationStrategy):
    def __init__(self, fmt: str):
        self.fmt = fmt

    def serialize(self, value: date) -> str:
        return value.strftime(self.fmt)

    def deserialize(self, value: str) -> date:
        return datetime.strptime(value, self.fmt).date()


class EthiopianDialect(Dialect):
    serialization_strategy = {date: DateTimeSerializationStrategy("%d/%m/%Y")}


@dataclass
class BaseEntity(DataClassDictMixin):
    class Config:
        code_generation_options = [ADD_DIALECT_SUPPORT]


@dataclass
class Entity1(BaseEntity):
    dt1: date


@dataclass
class Entity2(BaseEntity):
    dt2: date


entity1 = Entity1(date(2021, 12, 31))
entity2 = Entity2(date(2021, 12, 31))
try:
    print(entity1.to_dict(dialect=EthiopianDialect))
    print(entity2.to_dict(dialect=EthiopianDialect))
finally:
    print("Entity1", Entity1.__dialect_to_dict_cache__)
    print("Entity2", Entity2.__dialect_to_dict_cache__)

Output:

{'dt1': '31/12/2021'}
Entity1 {<class '__main__.EthiopianDialect'>: <function to_dict at 0x7fa213792dd0>}
Entity2 {<class '__main__.EthiopianDialect'>: <function to_dict at 0x7fa213792dd0>}
Traceback (most recent call last):
  File "/workspaces/ccn-api-server/scripts/demo/performance/issues/mashumaro_dialiect_issue.py", line 52, in <module>
    print(entity2.to_dict(dialect=EthiopianDialect))
  File "<string>", line 15, in to_dict
  File "<string>", line 3, in to_dict
AttributeError: 'Entity2' object has no attribute 'dt1'. Did you mean: 'dt2'?

Possible solution

In mashamuro/core/meta/builder.py - CodeBuilder the hasattr function is used to check if dialect_to_dict_cache exists in this class. Bus hasattr also searches in the BaseClasses. So instead of hasattr one could check in cls.__dict__ for the existence. So only the actual class is checked.

def add_to_dict(self) -> None:
        self.reset()
        dialects_feature = self.is_code_generation_option_enabled(ADD_DIALECT_SUPPORT)
        if dialects_feature:
            # self.add_line("if not hasattr(cls, '__dialect_to_dict_cache__'):") # CHANGED
            self.add_line("if not '__dialect_to_dict_cache__' in cls.__dict__:")  # CHANGED

            with self.indent():
                self.add_line("cls.__dialect_to_dict_cache__ = {}")
        if not dialects_feature or dialects_feature and self.dialect:
            return self._add_to_dict()

      ...
    
   def add_from_dict(self) -> None:
        self.reset()
        dialects_feature = self.is_code_generation_option_enabled(ADD_DIALECT_SUPPORT)
        if dialects_feature:
            #self.add_line("if not hasattr(cls, '__dialect_from_dict_cache__'):") # CHANGED
            self.add_line("if not '__dialect_from_dict_cache__' in cls.__dict__:") # CHANGED
            
            with self.indent():
                self.add_line("cls.__dialect_from_dict_cache__ = {}")
        if not dialects_feature or dialects_feature and self.dialect:
            return self._add_from_dict()
        ...

[Fatal1ty]

@QSHolzner

Thanks for spotting this bug! Fixed in 3.0.2.