Clarification about custom error type functionality with gRPC

[RedMarcher]

var InvalidArgument = Type("InvalidArgument", func() {
	Field(1, "field", String, "The name of the field that failed validation.")
	Field(2, "value", Any, "The invalid value provided for the field.")
	Required("field", "value")
})

var NotFound = Type("NotFound", func() {
	Field(1, "field", String, "The name of the field that was not found.")
	Field(2, "value", Any, "The requested value which was not found.")
	Required("field", "value")
})

1. Just to be clear, these custom error types will not extend any of the typical ErrorResult error fields right? We should redefine those fields manually?

2. Is it possible to have a "default" error message defined for an error? For example, for internal errors, since we don't want to expose any details, we would never have an err be passed into it. Instead, we want a message like "please contact support" to always be put in as the "error" message.

[raphael]

Hello,

1. Yes correct, these types define the complete error shape - independently of the default ErrorResult type used by Goa
2. It's possible to completely override how Goa serializes error responses using custom error formatters. Another approach could be using interceptors that change the content of errors before they get sent to the transport layer.