Disable proto2

[fdymylja]

Based on the discussion, since protov3 does not support extensions, which makes protoreflect fast paths implementation a lot more easier, we shoudl either disable proto2 support or fallback to the original codegen (and maybe output a warning?)

[aaronc]

How would the fallback look like?

[fdymylja]

How would the fallback look like?

Most likely I'd fall back to this function from protoc-gen-go -> https://github.com/protocolbuffers/protobuf-go/blob/v1.27.1/cmd/protoc-gen-go/internal_gengo/main.go#L68

[aaronc]

Basically anytime a message declares extensions ... to ... it would fallback? I also think it's fine to just fail.

[fdymylja]

Basically anytime a message declares extensions ... to ... it would fallback? I also think it's fine to just fail.

the fall back would be like -> if fileDescriptor.Syntax == "proto2" -> google-gen-go.GenerateFile.

Protobuf does not allow extensions unless you declare at top level this:

syntax="proto2";
...

Also for me failing is fine.

[aaronc]

Maybe an error is better for now since it's unintended usage?

[aaronc]

The only exception would be if we had to codegen for third-party files, but then you should just generate those separately

[fdymylja]

Maybe an error is better for now since it's unintended usage?

for me its fine to throw an error and say we don't generate files defined with proto2 syntax