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From "James E. King, III (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (THRIFT-3752) nil collections are serialized as empty collections
Date Wed, 22 Feb 2017 00:47:44 GMT

    [ https://issues.apache.org/jira/browse/THRIFT-3752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15877116#comment-15877116
] 

James E. King, III commented on THRIFT-3752:
--------------------------------------------

Is it possible THRIFT-4011 helped to resolve this issue?

> nil collections are serialized as empty collections
> ---------------------------------------------------
>
>                 Key: THRIFT-3752
>                 URL: https://issues.apache.org/jira/browse/THRIFT-3752
>             Project: Thrift
>          Issue Type: Bug
>          Components: Go - Compiler
>            Reporter: John Sirois
>            Assignee: John Sirois
>
> See discussion here: https://reviews.apache.org/r/45193/
> This is likely related to THRIFT-3700.
> In short, for this struct:
> {noformat}
> struct TaskQuery {
>     4: optional set<string> taskIds
> }
> {noformat}
> The following go struct is generated:
> {noformat}
> type TaskQuery struct {
> 	TaskIds  map[string]bool         `thrift:"taskIds,4" json:"taskIds"`
> }
> {noformat}
> 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:
> {noformat}
> 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
> }
> {noformat}
> 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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