Computed relationships are not consistent when used through RPC

Problem

Having a computed relationship like this:

CREATE FUNCTION test.computed_designers(x test.videogames) RETURNS SETOF test.designers AS $$
  SELECT * FROM test.designers WHERE id = $1.designer_id;
$$ LANGUAGE sql STABLE ROWS 1;

(Basically adding a named parameter x to the function we have in fixtures)

It will be callable and give a result like:

curl localhost:3000/rpc/computed_designers -H "Content-Type:application/json" -d @- <<EOF
{"x": {"designer_id": 2}}
EOF

[{"id":2,"name":"Hironobu Sakaguchi"}]

But [{"id":2,"name":"Hironobu Sakaguchi"}] is not a single object, thus inconsistent when using the function through computed rels:

curl 'localhost:3000/videogames?select=*,computed_designers(*)&id=eq.4'

[{"id":4,"name":"Final Fantasy II","designer_id":2,"computed_designers":{"id": 2, "name": "Hironobu Sakaguchi"}}]

Which gives {"id": 2, "name": "Hironobu Sakaguchi"} for the computed rel.

The option of changing the function to RETURNS test.designers comes to mind, that will work to give a single object through RPC, but now it would not work as computed relationship.

Proposal

Convert results of RPC that RETURNS SETOF test.designers ROWS 1 to a single json object.

Start with the RPC endpoint behavior and the computed relationship example, then inspect the referenced test/spec/fixtures/schema.sql function near the linked fixture lines. Compare the RPC and computed-relationship responses for RETURNS SETOF ... ROWS 1. Done means the RPC response is a single JSON object while the function remains usable as a computed relationship.