This package provides a convenient and performant way to use the standard gRPC error codes defined in https://grpc.github.io/grpc/core/md_doc_statuscodes.html.
Specifically, it provides:
- Static
varinstances of most status errors. - A
structwrapper around all status errors.
var instances are helpful because they allow you to use errors.Is from the Go Standard Library. For example, say you write a package to interact with a database and you need to handle a case where a lookup is not found. You could return grpcerrors.ErrNotFound in your package. Higher level code orchestrating the database lookup can use errors.Is(err, grpcerrors.ErrNotFound) if it needs to understand what type of error occured. If the error is appropriate to return through an API, this error object can be returned directly through a gRPC API without any conversions.
// TODO which others?
Status INVALID_ARGUMENT is notably not provided as a static var. The reason is because this error should be accompanied with a message describing which argument is invalid. A static var would create a data race in a concurrent execution environment, so it's avoided.
The struct wrappers are helpful when a using other libraries in the grpc-go ecosystem. For example, the gRPC status package implements a FromError function. This function declares an interface that requires GRPCStatus() be implemented. If it isn't, FromError converts a specific error into a vague unknown error. The grpc-gateway package is one such package where FromError is called. Without implementing GRPCStatus(), the JSON REST API returns an unknown error type - not very useful to the caller or for debugging purposes.
go get github.com/danielwchapman/grpcerrors