[Reopened] Incorrect json serialization of empty StringValue

[serhiikushch]

What version of protobuf and what language are you using?
Version: v3.9.1.
Language: PHP 7.3

What operating system (Linux, Windows, ...) and version?
Linux

What did you do?
I have a message defined as following:

syntax = "proto3";
package generated;

import "google/protobuf/wrappers.proto";

message Foo {
    Bar bar = 1;
}

message Bar {
    google.protobuf.StringValue field = 1;
}

What did you expect to see
When converting this message to json string like:

$message = new Foo(['bar' => new Bar(['field' => ''])])
echo $message->serializeToJsonString();

should return:

{"bar":{"field":""}}

What did you see instead?

{"bar":{"field":}}

that results in Syntax error after applying json_decode

Anything else we should know about your project / environment
I'm using c extension, however php package does not have this issue.
Detailed example with tests and docker file https://github.com/serhiikushch/protobuf-issue

[Sixuan]

Anyone can take a look at this issue? We've heard aa bunch of people that are having the same issue and had to switch to a different library.

Thanks!

[TeBoring]

testSerialize(string $expected, \Google\Protobuf\Internal\Message $message)

Does changing \Google\Protobuf\Internal\Message to the actual type solve the problem?

[TeBoring]

Seems the problem is because the array constructor with StringValue has some problems.
For now, could you use setter to set value?

[serhiikushch]

testSerialize(string $expected, \Google\Protobuf\Internal\Message $message)

Does changing \Google\Protobuf\Internal\Message to the actual type solve the problem?

No it's just type checking and changing it does not have any impact on functionality

Seems the problem is because the array constructor with StringValue has some problems.
For now, could you use setter to set value?

unfortunately not. we faced this issue on serializing GRPC service response(message structure is similar to my example)

[TeBoring]

Fixed in #6713