Changes between Version 1 and Version 2 of Ticket #29738

Timestamp:

Sep 6, 2018, 8:45:08 AM (6 years ago)

Author:

Simon Charette

Comment:

A solution could to make django.db.migration.serializer offer a way to register serializers for types and have django.contrib.postgres.App.ready() be in charge of registering the ones to handle psycopg2 range types.

If the registry uses an OrderedDict we should be able to replace ​that long series of if by iterating over the registry items.

registry = OrderedDict([
    (models.Field, ModelFieldSerializer),
    ...
])

def serializer_factory(value):
    if isinstance(value, Promise):
        value = str(value)
    elif isinstance(value, LazyObject):
        # The unwrapped value is returned as the first item of the arguments
        # tuple.
    value = value.__reduce__()[1][0]

    for type_, serializer_cls in registry.items():
        if isinstance(value, type_):
            return serializer_cls(value)
    raise ValueError(...)

The hasattr and checks could be performed using abcs.

from abc import ABC
class Deconstructable(ABC):
    @classmethod
    def __subclasshook__(cls, C):
        return hasattr(C, 'deconstruct')