computer-field.sql

-- this computed field will be used on the table "folders" named "has_access" returning a boolean
-- you can use it in your custom checks in select row permissions on "folders"!
CREATE OR REPLACE FUNCTION user_can_read_folder(folder_row folders, hasura_session json)
RETURNS boolean AS $$
  DECLARE
  	-- variables!
	current_user_id uuid;
  BEGIN
  	-- if, else, loops, queries, recursive calls, other functions, the sky is the limit!
	-- get the current user from hasura_session
	current_user_id := (VALUES (hasura_session ->> 'x-hasura-user-id'))::uuid;
	-- check that the user is a member of the project
	IF user_has_project_role(current_user_id, folder_row.project_id, '{"owner","administrator","standard","limited","disabled"}') THEN
		-- check that the user has read or write access on the folder
		RETURN user_has_folder_access(current_user_id, folder_row.id, '{"write","read"}');
	END IF;
	RETURN FALSE;
  END
$$ LANGUAGE plpgsql STABLE;

Nice, but unfortunately it does not work. At least I could not get it to work on Hasura version v2.3.1-cloud.1. Computed fields with more than one argument, even if it's hasura_session, are not made available in the permission setting interface.

If you don't need hasura_session then it's a great solution.