Allow map_to_openapi_type to be called like a function

[kasium]

Hi,

so I have a schema which uses a custom field. Currently you expect that we do the following:

ma = MarshmallowPlugin()

@ma.map_to_openapi_type(fields.Dict)
class Custom(field.Field): pass

However, it's not very nice if the fields are in separate files since you always need the MarshmallowPlugin instance. As a workaround, I figured out, that the decorator doesn't really change something in the class, therefore I can also write: ma.map_to_openapi_type(fields.Dict)(Custom). However, still not very nice syntax.

Therefore I would like to propose a new function which just takes the two args: ma.map_to_openapi_type2(Custom, fileds,Dict) (name can be improved 😄 ). This can then be called whereever the MarshmallowPlugin is created. What do you think?

[lafrech]

I see what you mean.

This is more or less what I do in flask-smorest: https://github.com/marshmallow-code/flask-smorest/blob/ec4fbecc71686535a38f8642760bab390f0fdc44/flask_smorest/spec/init.py#L269-L302.

The form

ma.map_to_openapi_type(fields.Dict)(Custom)

is not that terrible. Agreed it looks strange.

If we came up with a correct name, I wouldn't object to adding another function.

Or in the next major release we just drop the decorator form. It is not that useful since the class is not modified.

[kasium]

What do you think about create_type_mapping

[lafrech]

The more I think of it, the more I lean towards just removing the decorator form.

Let's do that in 6.0.

[lafrech]

@kasium, v6 is on its way so let's drop the decorator form and change it to function form.

You may send a PR if you want or I'll do it when I get the time.

[kasium]

@lafrech sounds great. I can create a PR in about two weeks. Does that work for you?

[lafrech]

@kasium, see #804.

[kasium]

Thanks, looks fine to me