What is the best way to handle post_dump hooks and "tweak" the generated spec?

[sirosen]

I have some schemas which handle some messy/complicated cases by means of (sometimes elaborate) pre_dump and post_dump hooks.

To give a (contrived) example, a schema might look like so:

class MySchemaEncodingAPeculiarList(Schema):
    data = fields.Nested(OtherSchema(many=True))

    @pre_dump
    def filter_data(self, data, **kwargs):
        contents = [x for x in data["foo"] if data["bar"][x] % 2 == 0]
        return {"data": contents}

    @post_dump
    def unwrap_data(self, obj, **kwargs):
        return obj["data"]

class MySchema(Schema):
    foos = fields.Nested(MySchemaEncodingAPeculiarList)

When my output schemas are passed into apispec, MySchema will show up something like

{
  "foos": {
    "data": [
      ...
    ]
  }
}

But the field data shouldn't really be there -- it's just an artifact of the way that these pre_dump and post_dump hooks are manipulating the data.

apispec cannot reasonably be asked to know what to do with this out of the box. post_dump and pre_dump hooks could do anything.

But I would like to know how I can or should customize the marshmallow plugin in order to handle MySchemaEncodingAPeculiarList, or maybe to handle it at the level of MySchema. I couldn't figure this out from the documentation, and would appreciate any help or guidance.

(I am also looking at restructuring the schemas, but the real use-case is a lot more complex than this toy example.)

[sponsfreixes]

Hi @sirosen, did you ever figure out how to resolve this issue? I am facing the same problem.

[sirosen]

It's unfortunately been a bit too long since I did my relevant work here for me to be sure, but I scanned my old code for this and it looked like my solution was to define a custom converter and restructure my schemas a little bit. It wasn't a "clean" job or anything generalizable though.

I think the production app where I did this at $WORK is too complex for me to extract an example. But I know that I learned a lot by looking at the oneofschema converter which someone produced as a separate library.