fix: fields extension on collections endpoint

[alukach]

Related Issue(s):

Description:

Currently, the fields extension fails on the Collections endpoint due to the fact that we process the include and exclude arguments as set() values and then attempt to convert it to JSON. set values are not supported by json.dumps and thus an error is thrown.

This PR converts these values to a list before json.dumps().

Additionally, I have added a test to validate this behavior. #327 and #328 came out of these tests, requiring the testing to be adjusted slightly.

PR Checklist:

• pre-commit hooks pass locally
• Tests pass (run make test)
• Documentation has been updated to reflect changes, if applicable, and docs build successfully (run make docs)
• Changes are added to the CHANGELOG.

[hrodmn]

Thanks for fixing this @alukach!

[hrodmn]

we should check to make sure this isn't coming from the pgstac side.

[vincentsarago]

FYI
The STAC Search model expects Sets https://github.com/stac-utils/stac-fastapi/blob/52a647af23af5dcb7d3c9a518f40db312bb4be5d/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/request.py#L21-L23

When we call self._clean_search_args in the all_collections method we directly apply json.dumps() on the response but for other methods (e.g item_collection) we put it back within the Pydantic model

stac-fastapi-pgstac/stac_fastapi/pgstac/core.py

Lines 402 to 413 in 990b2af

	clean = self._clean_search_args(
	base_args=base_args,
	filter_query=filter_expr,
	filter_lang=filter_lang,
	fields=fields,
	sortby=sortby,
	**kwargs,
	)
	try:
	search_request = self.pgstac_search_model(**clean)
	except ValidationError as e:

Hopefully Pydantic is smart enough to convert back end list to a set

from stac_fastapi.api.models import create_post_request_model
from stac_fastapi.pgstac.types.search import PgstacSearch
from stac_fastapi.extensions.core import FieldsExtension

post_request_model = create_post_request_model([FieldsExtension()], base_model=PgstacSearch)

# Normal input (set)
post_request_model(fields={"include": {"yo"}}).fields
>> PostFieldsExtension(include={'yo'}, exclude=set())

# Input with this PR (list)
post_request_model(fields={"include": ["yo"]}).fields
>> PostFieldsExtension(include={'yo'}, exclude=set())

# Check output json (Pydantic transform set to list) 
post_request_model(fields={"include": {"yo"}}).model_dump_json()
>> '{"collections":null,"ids":null,"bbox":null,"intersects":null,"datetime":null,"limit":10,"conf":null,"fields":{"include":["yo"],"exclude":[]}}'

[alukach]

Maybe I'm mistaken but there are no fields conformance class for collections (get_collections or get_collection) endpoint

Well I checked the PR and there is stac-api-extensions/fields#16 😓

but since we were supporting it, lets make it work 😅

I see you marked this comment as off-topic, but I will share that I was going off of: https://github.com/stac-api-extensions/collection-search/blob/v1.0.0-rc.1/README.md?plain=1#L103-L108

[vincentsarago]

@alukach @hrodmn added a passthrough to avoid Pydantic model validation when we have fields enabled (as we do for items)