ClusterAdmin swallows TopicError ErrMsg

[dnwe]

Versions

Sarama Version: e7238b1
Kafka Version: 1.1.1
Go Version: go1.10

Configuration

N/A

Logs

N/A

Problem Description

The ClusterAdmin interface added under #1055 provides an administrative client for Kafka similar to the official Java client based on design discussions under #1048

However, in the case of a TopicError being returned by one of the calls, only the underlying KError is returned to the user as it satisfies the built-in error interface.

https://github.com/Shopify/sarama/blob/e7238b119b7daab993720f0153eafb88e2b0ac1f/admin.go#L141-L148

However, in the case of (e.g.,) sarama.ErrPolicyViolation, sarama.ErrInvalidPartitions, sarama.ErrInvalidReplicaAssignment etc. there may well be a specific error message in the TopicError ErrMsg that is being hidden from the caller.

Shouldn't TopicError itself be extended to satisfy the error interface by appending any ErrMsg to the generic one?

e.g.,

type TopicError struct {
    Err    KError
    ErrMsg *string
}

func (t *TopicError) Error() string {
	text := t.Err.Error()
	if t.ErrMsg != nil {
		text = fmt.Sprintf("%s - %s", text, *t.ErrMsg)
	}
	return text
}

[dnwe]

Returning the full TopicError would allow type assertion to extract the kError and errMsg separately if that's appropriate too

[varun06]

@dnwe This should be fixed now right?

[dnwe]

Yep. Fixed be #1154