Context

The processWriteError func converts all errors chains that contain type driver.WriteCommandError into a mongo.WriteException, but discards the error chain. As a result, the additional context from all wrapped and joined errors is completely missing from the returned error. That means that joined retry errors (added with GODRIVER-3600) are never returned from write methods (e.g. InsertOne, UpdateOne, etc). We need to refactor processWriteError to maintain the error chains, similar to how wrapErrors works.

Definition of done

• Update processWriteError to wrap errors, not replace them.
  • Add an Unwrap() error func to mongo.WriteException and return the original error chain that was passed to processWriteError.
  • Update the mongo.WriteException error message to prevent duplication with the wrapped errors.
• Replace all direct error type assertions for the mongo.WriteException error type with calls to errors.As.
  • 24 type assertions, all in tests. See the results here.

Pitfalls

What should the implementer watch out for? What are the risks?