Standalone compiler

[Marcus-Rosti]

Short description

There should be a way to run the compiler in some standalone fashion. I've been trying to move our services to a monorepo built with bazel but there doesn't appear to be a way to standalone compile the protos to the akka-grpc style code.

Details

Build an executable jar and CLI for the akka-grpc scalapb compiler

[raboof]

Thanks for the feature request!

We might be pretty close to this, since we're already packaging up the code generation into jars with a main class to be used from the Gradle plugin:

• the akka-grpc-codegen module for our custom generators
• the akka-grpc-scalapb-protoc-plugin for the scala model classes

So it might be that all that's needed is to package those up a bit nicer and provide documentation on how to use them.

I'd be interested to hear how this goes!

[Marcus-Rosti]

I tried a good deal today to get the gradle plugin to be more executable friendly. But I nobly failed. I may just have to table this (my) project until y'all can do that! I'll keep watching the PRs!

[raboof]

Is there anything in particular you were having a hard time with? I'd be happy to try and give some more pointers.

[raboof]

I think both akka-grpc-codegen and akka-grpc-scalapb-protoc-plugin expect a CodeGeneratorRequest object on stdin (serialized with protobuf).

I'm not too familiar with Bazel, but I could imagine you could try:

• constructing such an object in the Bazel build
• using protoc in the Bazel build to construct and pass in this object
• adding options to our executable jars so we can build the CodeGeneratorRequest ourselves based on those

[Marcus-Rosti]

SO looks like it's pretty hard to get protoc to generate that intermediate form CodeGeneratorRequest just via the command line. It's does that via the plugin field for protoc a la scalapb: https://scalapb.github.io/scalapbc.html#using-scalapb-as-a-proper-protoc-plugin and https://github.com/scalapb/ScalaPB/blob/master/build.sbt#L302-L336

I think I'll have to package the codegen package here similarly.

[raboof]

I think I'll have to package the codegen package here similarly.

You should be able to use the codegen assembly jar (e.g. https://repo1.maven.org/maven2/com/lightbend/akka/grpc/akka-grpc-codegen_2.12/0.7.1/akka-grpc-codegen_2.12-0.7.1-assembly.jar) in this way I think.

[Marcus-Rosti]

I got this all to work! Thanks

[jsbrucker]

@ Marcus-Rosti I'm just starting to investigate using Bazel would it be possible for you to post a link to a repo that shows an example of what you did?

Update: https://github.com/akka/akka-grpc/issues/744#issuecomment-566580088