View Source Handling Errors
There are various options that can be set on the Domain module to determine how errors behave and/or are shown in the GraphQL.
Showing raised errors
For security purposes, if an error is raised as opposed to returned somewhere, the error is hidden. Set this to true
in dev/test environments for an easier time debugging.
graphql do
show_raised_errors? true
end
# or it can be done in config
# make sure you've set `otp_app` in your domain, i.e use Ash.Domain, otp_app: :my_app
config :my_app, YourDomain, [
graphql: [
show_raised_errors?: true
]
]
Root level errors
By default, action errors are simply shown in the errors
field for mutations. Set this to true
to return them as root level errors instead.
graphql do
root_level_errors? true
end
Error Handler
Setting an error handler allows you to use things like gettext
to translate errors and/or modify errors in some way. This error handler will take the error object to be returned, and the context. See the absinthe docs for adding to the absinthe context (i.e for setting a locale).
graphql do
error_handler {MyApp.GraphqlErrorHandler, :handle_error, []}
end
Keep in mind, that you will want to ensure that any custom error handler you add performs the logic to replace variables in error messages.
This is what the default error handler looks like, for example:
defmodule AshGraphql.DefaultErrorHandler do
@moduledoc "Replaces any text in message or short_message with variables"
def handle_error(
%{message: message, short_message: short_message, vars: vars} = error,
_context
) do
%{
error
| message: replace_vars(message, vars),
short_message: replace_vars(short_message, vars)
}
end
def handle_error(other, _), do: other
defp replace_vars(string, vars) do
vars =
if is_map(vars) do
vars
else
List.wrap(vars)
end
Enum.reduce(vars, string, fn {key, value}, acc ->
if String.contains?(acc, "%{#{key}}") do
String.replace(acc, "%{#{key}}", to_string(value))
else
acc
end
end)
end
end
Custom Errors
If you created your own Errors as described in the Ash Docs you also need to implement the protocol for it to be displayed in the Api.
defmodule Ash.Error.Action.InvalidArgument do
@moduledoc "Used when an invalid value is provided for an action argument"
use Splode.Error, fields: [:field, :message, :value], class: :invalid
def message(error) do
"""
Invalid value provided#{for_field(error)}#{do_message(error)}
#{inspect(error.value)}
"""
end
defimpl AshGraphql.Error, for: Ash.Error.Changes.InvalidArgument do
def to_error(error) do
%{
message: error.message,
short_message: error.message,
code: "invalid_argument",
vars: Map.new(error.vars),
fields: [error.field]
}
end
end
end