Some context to avoid the XY Problem: I’m trying to expose some state which lives in an external API as a resource field.
Let’s say I have a User
resource and I want to retrieve the URL for their Gravatar given their email. My understanding is that I can do this with a calculation
calculations do
calculate :gravatar_url, :string, User.Calculations.Gravatar
end
defmodule MyApp.User.Calculations.Gravatar do
use Ash.Calculation
alias MyApp.GravatarAPI
def calculate(users, _opts, _context) do
Enum.map(users, fn user ->
case GravatarAPI.fetch_url(user.email) do
{:ok, url} -> url
{:error, _} -> nil
end
end)
end
end
The problem with this solution is that if I retrieve a list of users using, e.g., GraphQL, the current implementation just silently returns nil
without letting the user know that, e.g., the API request failed for a specific user (which is something which can potentially be shown in GraphQL errors).
On the other hand, if I return {:error, :something}
if anything fails a single failed API request makes the calculation fails for all the users.
Is there a way around this? Am I using the wrong Ash tool?
The other possibility I thought of is using a resource with no data layer instead of a calculation. n that case, if I call both Simple.set_data
and Ash.Query.add_error
does the whole query fails (so nothing gets exposed from GraphQL) or is the partial data shown alongside the error?