Fix the incompatible encoding #336

[denverdino]

Fix #336

[codecov]

Codecov Report

Merging #337 into master will increase coverage by 0.19%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #337      +/-   ##
==========================================
+ Coverage   81.48%   81.68%   +0.19%     
==========================================
  Files          41       41              
  Lines        5013     5012       -1     
==========================================
+ Hits         4085     4094       +9     
+ Misses        807      798       -9     
+ Partials      121      120       -1

Impacted Files	Coverage Δ
reflect_marshaler.go	80.64% <100%> (-0.16%)	⬇️
reflect_struct_decoder.go	47.91% <0%> (+0.83%)	⬆️
stream.go	90% <0%> (+4%)	⬆️

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[thockin]

I am not very familiar with the code in question, but I don't immediately see what's changing here. Why is this better? Can you explain in the first PR comment?

@taowen can you please take a look? I don't want to have to carry a fork in Kubernetes :(

[denverdino]

@thockin

FYI,

In the "encoding/json", for the object with Marshaler interface, it will have extra step for encoding rather than use the MarshalJSON() result directly. That is why the incompatible behavior happens.

encoding/json/encode.go

func marshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
	if v.Kind() == reflect.Ptr && v.IsNil() {
		e.WriteString("null")
		return
	}
	m, ok := v.Interface().(Marshaler)
	if !ok {
		e.WriteString("null")
		return
	}
	b, err := m.MarshalJSON()
	if err == nil {
		// copy JSON into buffer, checking validity.
		err = compact(&e.Buffer, b, opts.escapeHTML)
	}
	if err != nil {
		e.error(&MarshalerError{v.Type(), err})
	}
}