ScalaPB

ScalaPB is a protocol buffer compiler (protoc) plugin for Scala. It will generate Scala case classes, parsers and serializers for your protocol buffers.

ScalaPB generates case classes that can co-exist in the same project alongside the Java-generated code for ProtocolBuffer. This makes it easy to gradually migrate an existing project from the Java version of protocol buffers to Scala. This is achieved by having the ScalaPB generated code use the proto file as part of the package name (in contrast to Java which uses the file name in CamelCase as an outer class)

Each top-level message and enum is written to a separate Scala file. This results in a significant improvement in incremental compilations.

Another cool feature of ScalaPB is that it can optionally generate methods that convert a Java protocol buffer to a Scala protocol buffer and vice versa. This is useful if you are gradually migrating a large code base from Java protocol buffers to Scala. The optional Java conversion is required if you want to use fromAscii (parsing ASCII representation of a protocol buffer). The current implementation delegates to the Java version.

Highlights

• Supports proto2 and proto3

• Easily update nested structure in functional way using lenses

• Scala.js integration

• GRPC integration

• Compatible with SparkSQL (through a helper library)

• Conversion to and from JSON

• Support user-defined options (since 0.5.29)

• Support extensions (since 0.6.0)

Versions

Version	Description
0.6.x	Stable. Supports Protobuf 2.6.x to 3.5.x
0.5.x	Supports Protobuf 2.6.x and Protobuf 3.1.x.
0.4.x	Stable, unsupported. Works with Protobuf 2.6.x

Installing

To automatically generate Scala case classes for your messages add ScalaPB's sbt plugin to your project. Create a file named project/protoc.sbt containing the following line:

addSbtPlugin("com.thesamet" % "sbt-protoc" % "0.99.18")

libraryDependencies += "com.thesamet.scalapb" %% "compilerplugin" % "0.7.1"

Add the following line to your build.sbt:

PB.targets in Compile := Seq(
  scalapb.gen() -> (sourceManaged in Compile).value
)

For additional configuration options, see ScalaPB SBT Settings documentation

Using ScalaPB

Documentation is available at ScalaPB website.

Testing

ScalaPB uses ScalaCheck to aggressively test the generated code. The test generates many different sets of proto files. The sets are growing in complexity: number of files, references to messages from other protos, message nesting and so on. Then, test data is generated to populate this protocol schema, then we check that the ScalaPB generated code behaves exactly like the reference implementation in Java.

Running the tests:

$ sbt test

The tests take a few minutes to run. There is a smaller test suite called e2e that uses the sbt plugin to compile the protos and runs a series of ScalaChecks on the outputs. To run it:

$ ./e2e.sh