Map fields generated by protoc fail with google-protobuf v4

[andreagasparin]

When generating JavaScript files from .proto using protoc (tested with version 32.1), the code for map fields calls serializeBinary() on jspb.Map instances. In google-protobuf@4.0.0, jspb.Map.prototype.serializeBinary no longer exists, causing runtime errors: "TypeError: f.serializeBinary is not a function".

I have a proto file that contains an element of type "map":
message TemplateEntity {
....
map<string, TemplateProperty> properties = 10;

message TemplateProperty {
...
}

In the generated file "..._pb.js" I see this code which seems incompatible with version 4:
...
f = message.getPropertiesMap(true);
if (f && f.getLength() > 0) {
f.serializeBinary(10, writer, jspb.BinaryWriter.prototype.writeString, jspb.BinaryWriter.prototype.writeMessage, proto.template.metadata.TemplateProperty.serializeBinaryToWriter);
}
...

[dibenede]

Have you regenerated your protobuf gen code since updating? When I inspect a _pb.js file generated by protoc-gen-js under 4.0.0 I see something different:

 // For a field map<string,string> map_string_string = ...;

  f = message.getMapStringStringMap(true);
  if (f && f.getLength() > 0) {
jspb.internal.public_for_gencode.serializeMapToBinary(
    message.getMapStringStringMap(true),
    69,
    writer,
    jspb.BinaryWriter.prototype.writeString,
    jspb.BinaryWriter.prototype.writeString);
  }

To be precise, when I say protoc-gen-js I mean the literal binary produced by building this package from source OR one of builds we provide on this github project.

We do not own https://www.npmjs.com/package/protoc-gen-js , which seems to still be using 3.21.4.

[andreagasparin]

Hi @dibenede,
Thanks for the quick response.
I can confirm that using version 4 of protoc-gen-js works.
I was fooled by the latest version at https://www.npmjs.com/package/protoc-gen-js, which isn't compatible with the one at https://www.npmjs.com/package/google-protobuf