Awesome

sbt-protoc

This plugin uses protoc to generate code from proto files. This SBT plugin is meant to supersede sbt-protobuf and sbt-scalapb.

Highlights

Generates source code directly under src_managed by default (works better with IntelliJ)
Supports compiling protos in both Test and Compile configuration.
Supports JVM-based code generators. Write your own custom code generator.
Straightforward: No PB.protobufSettings, packaged as auto-plugin.

Installation

Step 1: create project/protoc.sbt with:

addSbtPlugin("com.thesamet" % "sbt-protoc" % "1.0.7")

libraryDependencies += "com.thesamet.scalapb" %% "compilerplugin" % "0.10.10"

Step 2: add to build.sbt:

If you only want to generate Java code:

Compile / PB.targets := Seq(
  PB.gens.java -> (Compile / sourceManaged).value
)

A version of protobuf-java is going to get added to the runtime dependencies. To explicitly set this version you can write:

Compile / PB.targets := Seq(
  PB.gens.java("3.7.0") -> (Compile / sourceManaged).value
)

To pass generator parameters, for example to request the Java lite runtime, use:

Compile / PB.targets := Seq(
  Target(PB.gens.java, (Compile / sourceManaged).value, Seq("lite"))
)

For ScalaPB:

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

To generate Java + Scala with Java conversions:

Compile / PB.targets := Seq(
  PB.gens.java -> (Compile / sourceManaged).value,
  scalapb.gen(javaConversions = true) -> (Compile / sourceManaged).value
)

To make standard google.protobuf types available to import:

libraryDependencies ++= Seq(
  "com.google.protobuf" % "protobuf-java" % "3.13.0" % "protobuf"
)

The following includes both standard google.protobuf types and ScalaPB:

libraryDependencies ++= Seq(
    "com.thesamet.scalapb" %% "scalapb-runtime" % scalapb.compiler.Version.scalapbVersion % "protobuf"
)

Step 3: Put some protos in src/main/protobuf and compile

Download plugins that are available on maven repository

To download an artifact and use it as a code generator plugin:

libraryDependencies += "io.grpc" % "protoc-gen-grpc-java" % "1.23.0" asProtocPlugin()

Compile / PB.targets := Seq(
  PB.gens.plugin("grpc-java") -> (Compile / sourceManaged).value,
)

Note the asProtocPlugin provided to the dependency, this is equivalent to:

libraryDependencies += "io.grpc" % "protoc-gen-grpc-java" % "1.23.0" % "protobuf" artifacts(
  Artifact("protoc-gen-grpc-java", PB.ProtocPlugin, "exe", "linux-x86_64"))

with the operating system replaced accordingly to the system you are running on. You can use the full syntax in case the code generator you are trying to download follows a different pattern.

To invoke a plugin that is already locally installed

Compile / PB.targets := Seq(
  PB.gens.plugin(name="myplugin", path="/path/to/plugin") -> (Compile / sourceManaged).value / "js"
)

If you need to pass parameters to the plugin, it can be done as follows:

val grpcWebGen = PB.gens.plugin(
  name="grpc-web",
  path="/usr/local/bin/protoc-gen-grpc-web-1.0.7-linux-x86_64"
)

Compile / PB.targets := Seq(
  (grpcWebGen, Seq("mode=grpcwebtext")) -> (Compile / sourceManaged).value / "js"
)

Migration notes

From sbt-protoc 1.0.0 to 1.0.1

Protos imported with "protobuf-src" are now compiled only once per project, in the Compile configuration. Use Test / PB.protoSources += PB.externalSourcePath.value to trigger compilation also in Test (the previous behavior).
The cacheClassLoaders setting key is now deprecated as sbt-protoc now automatically reloads the class loaders used for sandboxing if it detects that the classpath it targets has changed since the last invocation. For advanced setups with a custom PB.artifactResolver returning different files on each invocation (and only for those), consider setting cacheArtifactResolution to false.

From sbt-protoc < 1.0.0 to 1.0.0

PB.protocVersion now accepts a version in x.y.z format (for example, 3.13.0). Previously, this key accepted protoc-jar style version flags such as -v361. Version 1.0.x of ScalaPB will strip out the -v part (a behavior that will be deprecated later), however it does not take version numbers without dot seperators.
Use PB.protocExecutable to use a locally installed protoc. By default this key downloads and caches protoc from Maven.
If you previously used protoc-jar's option --include_std_types, see Installation instructions above, and look for "To make standard google.protobuf types available to import"
Use PB.protocRun to have more control on how sbt-protoc invokes protoc (By default, it run PB.protocExecutable.

See CHANGELOG.md for more details.

Additional options

The options below need to be scoped to either Compile or Test (if unsure, you probably want Compile)

Example settings:

// Force the version for the protoc binary
PB.protocVersion := "3.21.7"

// Additional directories to search for imports:
Compile / PB.includePaths ++= Seq(file("/some/other/path"))

// Make protos from some Jar available to import.
libraryDependencies ++= Seq(
  "com.google.protobuf" % "protobuf-java" % "3.13.0" % "protobuf"
)

// Compile protos from some Jar (and make them available to import). Without
// the intrasitive() directory, `protobuf-src` would also unpack and compile
// all transitive dependencies of the package. This could lead to having
// duplicate class files, if another library is already providing compiled
// classes for your dependencies.
libraryDependencies ++= Seq(
  "com.google.api.grpc" % "proto-google-common-protos" % "1.17.0" % "protobuf-src" intransitive()
)

// Changing where to look for protos to compile (default src/main/protobuf):
Compile / PB.protoSources := Seq(sourceDirectory.value / "somewhere")

// Additional options to pass to protoc:
Compile / PB.protocOptions := Seq("-xyz")

// Excluding some proto files:
PB.generate / excludeFilter := "test-*.proto"

// Rarely needed: override where proto files from library dependencies are
// extracted to:
Compile / PB.externalIncludePath := file("/tmp/foo")

// By default we generate into target/src_managed. To customize:
Compile / PB.targets := Seq(
  scalapb.gen() -> file("/some/other/dir")
)

// Use a locally provided protoc (in 1.x):
PB.protocExecutable := file("/path/to/protoc")

// For sbt-protoc < 1.0 only:
Compile / PB.runProtoc := (args => Process("/path/to/protoc", args)!)

// Prevents the plugin from adding libraryDependencies to your project
PB.additionalDependencies := Nil

// Before version 0.99.15, when compiling in Windows, Python was used to bridge
// protoc and this JVM. To set the path for Python.exe:
// Note that this must be Python2 and not Python3.
// Since version 0.99.15 this option has no effect, and will be removed in a
// future version.
PB.pythonExe := "/path/to/python.exe"

// Disables the manifest processing feature of sbt-protoc that automatically
// adds option protos as a source file to protoc when `ScalaPB-Options-Proto`
// is found in a dependency jar manifest. This setting is turned on by default,
// and disabling it can lead to generation of code that does not compile due
// to inconsistent generator settings between your project and the dependencies
// added. See also https://scalapb.github.io/docs/customizations/#publishing-package-scoped-options
Compile / PB.manifestProcessing := false

Protos in other configs

This plugin supports generating protos in the Test config. That means, that you can put protos under src/test/protobuf and have it generated and compiled under the Test configuration, so the generated code is only available to your tests, but not to your main code.

To do that, add:

Test / PB.targets := Seq(
    PB.gens.java("3.11.4") -> (Test / sourceManaged).value
)

If you want to have protos in some other configuration (not Compile or Test), for example IntegrationTest you need to manually add the plugin default settings in that configuration:

configs(IntegrationTest)

inConfig(IntegrationTest)(sbtprotoc.ProtocPlugin.protobufConfigSettings)

IntegrationTest / PB.targets := Seq(
    PB.gens.java("3.11.4") -> (IntegrationTest / sourceManaged).value
)

Debugging

Show proto files extracted and where there are coming from:

sbt> set logLevel := Level.Debug
sbt> protocUnpackDependencies

IntelliJ IDEA BSP bug

IntelliJ has a bug where it only recognizes generated sources if there is at least one Scala class in the same package - otherwise you'll see red squiggles. As a workaround, you can configure your project to add a private empty class, e.g. like this:

Compile / sourceGenerators += Def.task {
  // adapt this for your build:
  val protoPackage = "org.example.proto.foo"
  val scalaFile = (Compile/sourceManaged).value / "_ONLY_FOR_INTELLIJ.scala"
  
  IO.write(scalaFile,
    s"""package $protoPackage
      |
      |private class _ONLY_FOR_INTELLIJ
      |""".stripMargin)
  Seq(scalaFile)
}.taskValue