protostub

protostub

A tool for generating Mypy type stubs from a Protocol Buffer definition.

Usage

You can download a binary from the releases page, or you can use Docker.

Assuming that you have a .proto file called foo.proto and you want to generate a .pyi file from it, usage is as such:

protostub generate --proto foo.proto

In this case, protostub assumes you want to call your stub foo_pb2.pyi. If this is not the case, or perhaps you want to specify a different directory, the output can be specified like so:

protostub generate --proto foo.proto --mypy bar.pyi

Help is included in the tool:

Generate Mypy type stubs from Protobuf definitions

Usage:
  protostub [command]

Available Commands:
  generate    Generate a stub from a given proto file
  help        Help about any command

Flags:
  -h, --help   help for protostub

Use "protostub [command] --help" for more information about a command.

Using the stubs

If you've tried using mypy in your project, you've probably noticed that it does not do anything for protobuf types. This is because the generated python contains nothing that Mypy can use - classes are not defined in the "normal" way.

We currently use a script to generate a list of files for Mypy to check. If the .py file has a corresponding .pyi file, then the .py is ignored. Otherwise it is used. This allows us to override any Python with a type stub, meaning we can override Python generated by protoc with something generated by protostub, and get functioning type checks!

An alternative would be to invoke Mypy on a module rather than on files, and provide the stubs in MYPYPATH. However, I have not tested this, so I don't know how well it works.

Docker

A docker image is also provided! The easiest way for you to use this is as follows (assuming there is a file called foo.proto in the current directory):

docker run -v $(pwd):/protostub protostub:latest generate -p foo.proto

After doing this, you should see the help text.

Building

Requirements

• Go
• make (optional)

With go get

If you already have Go all setup in your PATH, then it is as simple as:

go get github.com/arachnys/protostub/cmd/protostub

With Make

This approach might be best if you're less familiar with Go, and want it to just work. It requires no messing with $GOPATH.

git clone https://github.com/arachnys/protostub
cd protostub
make

The protostub binary should be in the bin folder.

License

The MIT License (MIT)
Copyright © 2018 Arachnys Information Services Ltd and individual contributors.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.