POST /store/<store_id>/tag fails on Render with Marshmallow

[SANDEEPNEGI07]

Description

When deploying the project to Render, the POST /store/<store_id>/tag endpoint crashes.
The same request works locally with insomnia client, but fails on Render due to some Marshmallow behavior.

Steps to Reproduce

1. Deploy the project to Render.
2. Send a POST request to /store/1/tag with body:

{
  "name": "Food"
}

The server responds with an error:

'dict' object has no attribute '_sa_instance_state'

Solution

@blp.response(200, TagSchema)    # Response can include items and store
def post(self, tag_data, store_id):
    if TagModel.query.filter(
        TagModel.store_id == store_id,
        TagModel.name == tag_data["name"]
    ).first():
        abort(400, message="A tag with that name already exists in that store.")

    tag = TagModel(**tag_data, store_id=store_id)

    try:
        db.session.add(tag)
        db.session.commit()
    except SQLAlchemyError as e:
        abort(500, message=str(e))

    return tag

The correct fix is to separate schemas (PlainTagSchema for input, TagSchema for output).

I hope this bug solution will help you.

[SANDEEPNEGI07]

My insomnia client was working fine but on testing my deployed project gives an error when sending the json to the POST /store/<store_id>/tag.

So as a solution:

i passed PlainTagSchema as the agrument

• @blp.argument(PlainTagSchema)

TagSchema in the response

• @blp.response(200, TagSchema)