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  1. Thrift
  2. THRIFT-3752

nil collections are serialized as empty collections



    • Type: Bug
    • Status: In Progress
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: Go - Compiler
    • Labels:


      See discussion here: https://reviews.apache.org/r/45193/
      This is likely related to THRIFT-3700.

      In short, for this struct:

      struct TaskQuery {
          4: optional set<string> taskIds

      The following go struct is generated:

      type TaskQuery struct {
      	TaskIds  map[string]bool         `thrift:"taskIds,4" json:"taskIds"`

      This is all well and good, since TaskQuery{}.TaskIds == nil; ie the TaskIds collection field is - by default - unset.

      The problem is in the serialization for the field, which wipes out the unset (nil) vs empty collection distinction at the wire level:

      func (p *TaskQuery) writeField4(oprot thrift.TProtocol) (err error) {
      	if err := oprot.WriteFieldBegin("taskIds", thrift.SET, 4); err != nil {
      		return thrift.PrependError(fmt.Sprintf("%T write field begin error 4:taskIds: ", p), err)
      	if err := oprot.WriteSetBegin(thrift.STRING, len(p.TaskIds)); err != nil {
      		return thrift.PrependError("error writing set begin: ", err)
      	for v, _ := range p.TaskIds {
      		if err := oprot.WriteString(string(v)); err != nil {
      			return thrift.PrependError(fmt.Sprintf("%T. (0) field write error: ", p), err)
      	if err := oprot.WriteSetEnd(); err != nil {
      		return thrift.PrependError("error writing set end: ", err)
      	if err := oprot.WriteFieldEnd(); err != nil {
      		return thrift.PrependError(fmt.Sprintf("%T write field end error 4:taskIds: ", p), err)
      	return err

      So on the receiving end of the wire, a nil collection is turned into an empty collection and so unset-ness cannot be distinguished from set but empty.


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              • Assignee:
                jsirois John Sirois
                jsirois John Sirois
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