JSON transcoding has backwards incompatible change in 1.27.0, due to json_name field always populated by protoc

[C0mbatwombat]

Hi,

In #5193 functionality was added so that if a user sets the json_name field in the .proto file explicitly, it is used to resolve the path & query params when doing transcoding. This makes perfect sense, if it weren't for a bug in protoc: the proto compiler always populates the json_name field since 3.1.0.

This means that to retain our existing behaviour (using the original field which might contain underscores) we have to add json_name = <field_name> to all our proto definitions.

The Protobuf code base also acknowledges it as a bug and has a workaround to deal with it.

I suppose Armeria needs to use the same workaround as the protobuf codebase: if the json_name that is set is the same as the default calculated one, assume it was not set explicitly by the user.

Thanks!

[mbgit2]

Any update on this? I'm currently stuck on 1.26.4 due to this.

[ikhoon]

I suppose Armeria needs to use the same workaround as the protobuf codebase: if the json_name that is set is the same as the default calculated one, assume it was not set explicitly by the user.

It makes sense. We may provide a new option to ignore json_name. Let us handle it in the next version.

[ikhoon]

I've compiled a proto file with protoc 3.25.1 and json_name was empty if it is not set.

armeria/dependencies.toml

Line 119 in 683bd74

protobuf = "3.25.1"

Was that bug fixed in recent versions or am I missing something to reproduce the problem?

[mbgit2]

For us it doesn't seem fixed. We have a custom interceptor, but this now gets a complete empty (ReqT message) argument when using transcoding.

[berendjan]

Hi @ikhoon,
we're also encountering the problem but only when using plugins. As noted in the code base:
"json_name option is not allowed on extension fields. Note that the json_name field in FieldDescriptorProto is always populated by protoc when it sends descriptor data to plugins"

If you add a plugin you will see the filled in json_name.
In our setup we use https://github.com/bufbuild/protoc-gen-validate leading to the same problem

Thanks!

[ikhoon]

I failed to reproduce the problem by configuring https://github.com/bufbuild/protoc-gen-validate. Would you provide a minimal reproducible example? The example should be useful for preventing regression and ensuring compatibility.