在导入的结构上覆盖结构字段标签

Question

I have a third party client library (Sarama) that exposes a configuration struct.

I want to reference that struct directly from my configuration struct:

type MyConfig struct {
  Sarama sarama.Config
}

I am using go-yaml to marshal my configuration. Marshalling MyConfig with go-yaml panics because sarama.Config contains a field (Partitioner) that is of type func and the yaml parser doesn't know how to Marshal a func.

A way of preventing this panic would be to tell go-yaml to ignore this field (using the tag yaml:"-" on the field) but I am unable to set tags on a struct that isn't defined in my code.

Is there an elegant go way to include this configuration in my own configuration and not cause the go-yaml marshaller to panic? Should I try and override the tag or should I copy the struct into my own code and write a converter?

Answer 1

I have always had problems with go-yaml. The library is not in a good design. However it is the most effective tool at hand, at least for now.

There is some way to hide from encoding/json but I tested it does not work for go-yaml. However, go-yaml does provide a way to extend its capacity (though it is very awkward).

As I see in your code, that Partitioner is of type PartitionerConstructor, a custom type, so you can make PartitionerConstructor implents yaml.Marshaler interface:

func (PartitionerConstructor) MarshalYAML() (interface{},error) {
        return nil,nil
}

Note that it will generate a Partitioner: null line, but it will get around from panic.