FastAPI JSON weird

So, I’m not sure which library bears responsibility here, but I’ll start with ormar and you can forward me somewhere else if the problem lies elsewhere. Consider the following code:

...
class Thing(ormar.Model):
    class Meta(BaseMeta):
        tablename = "things"
    id: UUID = ormar.UUID(primary_key=True, default=uuid4)
    name: str = ormar.Text(default="")
    js: pydantic.Json = ormar.JSON()
...
@app.get("/things")
async def read_things():
    return await Thing.objects.all()
...

What I get when I call this endpoint is e.g.

[
  {
    "id": "1932caad-1157-4224-9688-e280f9623e67",
    "name": "",
    "js": "[\"asdf\", \"asdf\", \"bobby\", \"nigel\"]"
  },
  {
    "id": "3e6a15b2-2cd5-456b-a4dc-24e3cd76d96e",
    "name": "test",
    "js": "[\"lemon\", \"raspberry\", \"lime\", \"pumice\"]"
  }
]

Note how rather than being JSON, the js field is a plain string containing JSON. Is this on purpose? Does it HAVE to be that way? It seems to me like it would make more sense for a JSON field, when its container is serialized to JSON, to just…be JSON. (I note that thing.json() preserves the “convert json to string” behavior.) Is there an easy way around this behavior, perhaps a flag or setting? Is this actually a result of a different library?

[Erhannis]

Great, that works. Thanks! I’ll open more tickets if I find anything else weird or wrong.

On Mon, Feb 15, 2021, 2:10 PM collerek [e-mail] wrote:

Yeah, it was changed in one of the old version to be in line with pydantic where you have to specifically set field to optional or provide a default value for the field to be not required. See that i forgot to update the nullable part of docs, thanks for the tip, will change that.

As for the rules below is the section from the docs overview:

All fields are required unless one of the following is set:

• nullable - Creates a nullable column. Sets the default to None.
• default - Set a default value for the field.
• server_default - Set a default value for the field on server side (like sqlalchemy’s func.now()).
• primary key with autoincrement - When a column is set to primary key and autoincrement is set on this column. Autoincrement is set by default on int primary keys.
• pydantic_only - Field is available only as normal pydantic field, not stored in the database.

So in your case you should just set nullable=True on js Field.

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[collerek]

Yeah, it was changed in one of the old version to be in line with pydantic where you have to specifically set field to optional or provide a default value for the field to be not required. See that i forgot to update the nullable part of docs, thanks for the tip, will change that.

As for the rules below is the section from the docs overview:

All fields are required unless one of the following is set:

• nullable - Creates a nullable column. Sets the default to None.
• default - Set a default value for the field.
• server_default - Set a default value for the field on server side (like sqlalchemy’s func.now()).
• primary key with autoincrement - When a column is set to primary key and autoincrement is set on this column. Autoincrement is set by default on int primary keys.
• pydantic_only - Field is available only as normal pydantic field, not stored in the database.

Also relation fields by default are nullable.

So in your case you should just set nullable=True on js Field.