error with null datetime

[jonhealy1]

I was looking at upgrading stac-pydantic and I noticed that it does not like: "datetime": null in a stac item. I got this error message running pytest as well. I think this line needs to be changed:

stac-pydantic/stac_pydantic/item.py

Line 23 in c2db77c

datetime: Union[dt, str] = Field(..., alias="datetime")

$ stac-pydantic validate-item https://raw.githubusercontent.com/radiantearth/stac-spec/master/examples/collectionless-item.json

1 validation error for CustomStacItem
properties -> datetime
  none is not an allowed value (type=type_error.none.not_allowed)

• To get this error you need to change the version to '1.0.0-rc.4' in version.py

[jonhealy1]

It says here that null is allowed for datetime: https://github.com/radiantearth/stac-spec/blob/v1.0.0-beta.2/item-spec/item-spec.md

[jonhealy1]

I tried this datetime: Union[dt, str] = Field(None, alias="datetime") but then this test fails test_validate_item_reraise_exception because it is allowing an item with no datetime key whatsoever to pass.

[geospatial-jeff]

I think maybe we can update the ItemProperties.datetime type to 'Optional[datetime] = Field(...)'

The '...' indicates the field is required, so a user has to explicitely pass 'None'. I don't have the pydantic docs in front of me (I'm on mobile atm) but I think this is how it works.

This is kind of related to #74 and #75

[jonhealy1]

Do you think that in "datetime": null, the problem is that null should be None for Python?

[kylebarron]

A JSON null is equivalent to a Python None. When you call json.load on that JSON document, you'll get 'datetime': None

[alukach]

I do believe that we should instead be expecting None rather than "null". See #116 for a PR.