Inherit ordered schemas when Meta is defined

[frol]

No description provided.

[frol]

I have reimplemented this feature in a cleaner way. Originally, I patched the meta instance right in the __new__.

[sloria]

We should not be messing with Python's inheritance behavior any more than necessary. class Meta can be inherited just like a normal class.

from marshmallow import Schema

class Parent(Schema):
    class Meta:
        ordered = True


class Child(Schema):
    class Meta(Parent.Meta):
        pass

assert Child().opts.ordered is True

[frol]

Without this change we have inconsistent behavior as ordered is inferred from base classes in __new__, so I believe that either you drop that logic (that would be sad) or complete it with this change.

[frol]

I am talking about these lines:

marshmallow/marshmallow/schema.py

Lines 84 to 97 in 596015a

	if not ordered:
	# Inherit 'ordered' option
	# Warning: We loop through bases instead of MRO because we don't
	# yet have access to the class object
	# (i.e. can't call super before we have fields)
	for base_ in bases:
	if hasattr(base_, 'Meta') and hasattr(base_.Meta, 'ordered'):
	ordered = base_.Meta.ordered
	break
	else:
	ordered = False
	cls_fields = _get_fields(attrs, base.FieldABC, pop=True, ordered=ordered)
	klass = super(SchemaMeta, mcs).__new__(mcs, name, bases, attrs)
	inherited_fields = _get_fields_by_mro(klass, base.FieldABC, ordered=ordered)

. You infer the ordered option there and since you already treat the schema as ordered, it is absolutely fine to help the SchemaOpts to set the ordered value correctly.

This behavior was introduced 2 years ago in 927704b to close #162.

BTW, if the Meta is inherited, we won't break anything as ordered is checked on the Meta:

marshmallow/marshmallow/schema.py

Line 83 in 596015a

ordered = getattr(meta, 'ordered', False)

[sloria]

OK, thanks for your input. I will take a closer look at this when I have the time.

[sloria]

@frol OK, this looks like a good change. Since this is a bug fix, would you mind resending the PR to the 2.x-line branch?

[frol]

Thank you for your review! I agree it is should be in 2.x-line. I will do this shortly.

[frol]

Rebased and changed the target branch.

[sloria]

Thanks for the quick turnaround!