Feature Request: make protocol buffer AST/parser SDK

[Gerardo Mora]

Hello everyone, I would like to create an application that analyzes a .proto file and dynamically creates GraphQL queries, I don't want to parse the .proto files because it will outdated and probably buggy at some point, but I was reading the source code and the only available thing is create a plugin that ouputs a file after the processing which is not idea.

Is there an API/SDK available for it?  

[Marc Gravell]

You can use protoc to output the compiled schema (one of the command-line-options - something "file descriptor set"), and deserialize the resultant binary file as a FileDescriptorSet instance, deserializing via your choice of language via descriptor.proto - any use?

As an aside, I also have a separate implementation of a .proto parser, implemented in C#/.NET (so it can be used in 100% managed .NET code). Not sure if that is any use to you, but if so: let me know.

On Wed, 17 Feb 2021, 00:12 Gerardo Mora, <gmoras...@gmail.com> wrote:

Hello everyone, I would like to create an application that analyzes a .proto file and dynamically creates GraphQL queries, I don't want to parse the .proto files because it will outdated and probably buggy at some point, but I was reading the source code and the only available thing is create a plugin that ouputs a file after the processing which is not idea.

Is there an API/SDK available for it?  

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[Derek Perez]

It sounds like you may wanna build a protoc plugin like so:

https://expobrain.net/2015/09/13/create-a-plugin-for-google-protocol-buffer/

The AST for protobuf is actually in protobuf itself! It's very easy to work with, and is the backbone of all the code generators.

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[Gerardo Mora]

I'm gonna use golang for my project, and will be open source, so eventually I will show you the software if you guys are interested!

I would like that the parser will run in the same thread of the request, when a microservice registers itself.

I'm gonna read all approaches and see, thanks guys!

PS 

if there are more ideas all are welcomed.

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May the source be with you!!!

[Josh Humphries]

If you are using Go, you can use this protoparse package to parse proto source:
https://pkg.go.dev/github.com/jhump/protoreflect/desc/protoparse

It provides functions for parsing and linking into descriptors. But it also provides an option to parse into a richer AST. The descriptor format is not a particularly good AST because it is lossy. So if you wanted to write a formatter, for example, the descriptor loses a lot of token position and comment information, which may prevent you from perfectly reconstructing the original source text. The ast sub-package of protoparse is not lossy and includes position information, including whitespace and comments, for everything lexed token.
https://pkg.go.dev/github.com/jhump/protoreflect/desc/protoparse/ast

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Josh Humphries
jh...@bluegosling.com

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[Gerardo Mora]

excellent option, I will use it!

[Lim Afriyadi]

I've created a PoC to automate GraphQL API creation (code first approach) from protobuf using protobuf extension to define graphql query / mutation name. I'm using protogen package to iterate protobuf file definition. Maybe you would like to take a look https://github.com/ncrypthic/graphql-grpc-edge.