Error: grpc-js doesn't work with FlatBuffer message (message.copy is not a function)

Problem description

gprc (native node module) works with FlatBuffers message but pure js version seems to be buggy with it.

Reproduction steps

1. Write a .fbs schema file with RPC service, generate JS, TS definitions
2. In JS code, create a message using FlatBuffers builder, example:

    const server = new PAuthClient(ServerURL, ServerCertificate)
    const builder = new flatbuffers.Builder() // create message
    
    const email = builder.createString(this.email) // add fields to message
    const password = builder.createString(this.password)  // add fields to message
    
    const service = builder.createString('___')
    const root = PAuthRequest.createPAuthRequest(builder, email, password, service)
    builder.finish(root)
    
    const buffer = PAuthRequest.getRootAsPAuthRequest(new flatbuffers.ByteBuffer(builder.asUint8Array()))

    // below code works with grpc native, but with grpc-js, errors printed:
    // INTERNAL: message.copy is not a function
    server.Authenticate(buffer, (err, response) => {
    })

Environment

• OS name, version and architecture: Ubuntu 20.04 amd64
• Node version: v12.13.0
• Node installation method: nvm
• Package name and version: grpc-js - 1.5.10

[murgatroid99]

I think this is likely to be an error in the code generator. The object that ends up being message is the output of a serialize function, which is a function signature that returns a Buffer in both libraries. Since the Buffer class has a copy method, I can only assume that some other object made its way into that code path, and since the serialize function is provided by the code generator, that’s where the problem probably is.

My guess is that, since neither library calls every method of the Buffer class, the FlatBuffer code generator was able to get away with providing some other object that happens to implement the subset of the Buffer API that the grpc library uses. But that is just coincidental compatibility.

[manhnt9]

Yep, I should try upgrading to new FlatBuffers since I saw this line in its latest release: “Overhaul of TypeScript support.” Thanks !

Can be closed for now.