Add nanopb plugin

[scootermon]

Closes #683

This PR is marked as a draft because of the following open points:

1. still need to successfully run the tests (ran into issues with my devcontainer setup)
2. nanopb has a runtime dependency on a few c files. Since there isn't really an established library ecosystem for C (and especially not in embedded circles where you would use nanopb) we need to find an alternative like copying the files to the output. Does buf already have a way to deal with this?

[CLAassistant]

All committers have signed the CLA.

[pkwarren]

Looks great - just a few suggestions on the Dockerfile.

[pkwarren]

nanopb has a runtime dependency on a few c files. Since there isn't really an established library ecosystem for C (and especially not in embedded circles where you would use nanopb) we need to find an alternative like copying the files to the output. Does buf already have a way to deal with this?

Are you talking about using this plugin as a Generated SDK? If so you are correct and there isn't support for C programs today. This plugin would be available initially only as a Remote Plugin.

If you wish for the plugin itself to include additional C files in the output, it would need to ship them in the nanopg generator plugin itself using the file field on CodeGeneratorResponse: https://github.com/protocolbuffers/protobuf/blob/396d6617674622bf9be4b73088f2f17e9f6eb374/src/google/protobuf/compiler/plugin.proto#L179.

[scootermon]

Are you talking about using this plugin as a Generated SDK? If so you are correct and there isn't support for C programs today. This plugin would be available initially only as a Remote Plugin.

That's fine then, I just wanted to make sure I would add it as well in case it's already supported by nanopb.

If you wish for the plugin itself to include additional C files in the output, it would need to ship them in the nanopg generator plugin itself using the file field on CodeGeneratorResponse

Makes sense, that's something that would have to be implemented in nanopb itself then.

---

I went ahead and applied your suggestions, updated the PR, and marked it as ready.

[mfridman]

lgtm, thanks for taking the time to contribute 🥳.

[scootermon]

Thanks guys!
You both made this a great contributing experience and I really appreciate that!

[mfridman]

Awesome, the plugin has been published via the automation in this repository to https://buf.build/community/nanopb

Took it for a spin

# buf.gen.yaml
version: v1
managed:
  enabled: true
plugins:
  - plugin: buf.build/community/nanopb:v0.4.8
    out: gen

And then generated some code

buf generate buf.build/acme/petapis --include-imports

output

gen
├── google
│   └── type
│       ├── datetime.pb.c
│       ├── datetime.pb.h
│       ├── money.pb.c
│       └── money.pb.h
├── payment
│   └── v1alpha1
│       ├── payment.pb.c
│       └── payment.pb.h
└── pet
    └── v1
        ├── pet.pb.c
        └── pet.pb.h