ConnectionString::parse will return an empty ConnectionString (which will return false on calls to isValid()) on certain kinds of invalid input.

It also, however, calls the HostAndPort constructor, which can throw an exception on invalid input (and prints a stack trace). This means that ConnectionString::parse has inconsistent behavior on invalid input.

The simple approach of catching the exception thrown by HostAndPort() would work, but still presents a user experience problem as a stack trace will still print for the error thrown.