How to modify Metadata model without copying all the code

[robintw]

I couldn't work out a good title for this - sorry!

I have an application which is using titiler-pgstac as a dependency: we don't have the whole titiler-pgstac source copied into our app, we just import the relevant bits and build up our own FastAPI application. We'd like to keep it like this if at all possible - I think this is the way it's meant to be used, and it definitely works far better for us (we've tried both ways).

However, we would also like to modify the Metadata model, as we want to change exactly what is stored in the metadata - for example, convert the assets list into an assets dictionary, so we can store more information about the assets for downstream applications to use.

Is it possible to modify the definition of a pydantic model that is deep inside titiler-pgstac, without having to basically copy in all of the titiler-pgstac code?

I've managed to do this in a 'hacky' way by doing something like this at the top of my main application file:

# Alter the metadata specification so that the assets list becomes
# a dictionary, so we can store more information about the assets
class AAMetadata(Metadata):
    assets: Optional[Dict[str, Any]]

class AASearch(Search):
    metadata: AAMetadata

class AAInfo(Info):
    search: AASearch

titiler.pgstac.model.Metadata = AAMetadata
titiler.pgstac.model.Search = AASearch
titiler.pgstac.model.Info = AAInfo

But it's not very nice.

Is there a nicer way of doing this? I was hoping to find some way of passing the models in as a dependency, but I can't seem to find that. I'm relatively inexperienced with FastAPI, so I may be missing a way of doing this.

[vincentsarago]

👋
Metadata allows extra(https://github.com/stac-utils/titiler-pgstac/blob/master/titiler/pgstac/model.py#L103) attribute so you could in theory just add another property in the Metadata like assets_properties: Optional[Dict[str, Any]] when you register your Search request. The only downside is that it won't show up in the OpenAPI schema

[robintw]

Thanks @vincentsarago, using something like asset_properties works well.