marshmallow-code / marshmallow-code/marshmallow

Configuring only, exclude, load_only, and dump_only on fields.Nested()

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Python
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Description

ref https://github.com/marshmallow-code/marshmallow/pull/572

There are currently a number of inconsistencies with configuration of `only`, `exclude`, `load_only`, and `dump_only` on `fields.Nested`.

The biggest one is that `only` and `exclude` are specified when constructing the `fields.Nested`, but `load_only` and `dump_only` come from dot-delimited fields on the `Schema`.

Additionally, the `only` parameter on `fields.Nested` takes a string, while `exclude` does not – and `only` and `exclude` on `Schema` both only take a string.

I would like to be able to use syntax like `fields.Nested(ChildSchema, dump_only=('child.id',))`. However, it's not clear to me how this would interact with the options passed in at schema construction time.

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Research direction

Review the fields.Nested configuration and the Schema options for only, exclude, load_only, and dump_only, then compare the behavior described in the issue with pull request 572. Clarify how constructor-time and schema-level options should interact, including the proposed dotted-field syntax. Done means the configuration rules are consistent and the supported behavior is verified.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
backend
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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