Edit

Gradle

Gradle is a build tool that can be used easily with a large number of programming languages including Scala. With it you can easily define your builds for Groovy or Kotlin, which enables for a high degree of customization. You can look up all the possible features on the Gradle website.

Automatic installation

The first time you open Metals in a new workspace it prompts you to import the build. Select "Import build" to start automatic installation. After it's finished you should be able edit and compile your code.

Manual installation

In a highly customized workspaces it might not be possible to use automatic import. In such cases there is a number of steps required to generate the needed Bloop config.

First we need to add the Bloop plugin dependency to the project, it should be included in the buildscript section:

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'ch.epfl.scala:gradle-bloop_2.12:1.3.3'
    }
}

Secondly, we need to enable the plugin for all the projects we want to include, it's easiest to define it for allprojects:

allprojects {
   apply plugin: bloop.integrations.gradle.BloopPlugin
}

Now we can run gradle bloopInstall, which will create a Bloop configuration files.

This will enable us to work with Metals and all features should work.

However, for all versions before and including 0.7.6 we need a couple more steps.

First, we need to add the SemanticDB plugin. This can be done by adding a couple of options to the Scala compiler:

allprojects {
    afterEvaluate {
        configurations {
            scalaCompilerPlugin
        }
        dependencies {
            scalaCompilerPlugin "org.scalameta:semanticdb-scalac_$scalaVersion:4.2.3"
        }
        def pluginFile = project.configurations.scalaCompilerPlugin.find {
            it.name.contains("semanticdb")
        }
        if (!pluginFile) {
            throw new RuntimeException("SemanticDB plugin not found!")
        }
        tasks.withType(ScalaCompile) {
            def params = [
                '-Xplugin:' + pluginFile.absolutePath,
                '-P:semanticdb:synthetics:on',
                '-P:semanticdb:failures:warning',
                '-P:semanticdb:sourceroot:' + project.rootProject.projectDir,
                '-Yrangepos',
                '-Xplugin-require:semanticdb'
            ]
            if (scalaCompileOptions.additionalParameters)
                scalaCompileOptions.additionalParameters += params
            else
                scalaCompileOptions.additionalParameters = params
        }
    }
}

You need to also define scalaVersion which corresponds to the scala version in your project. We also use afterEvaluate here so that we have scala dependency and all build specific scala compiler options defined before adding the SemanticDB plugin. It might be not needed in your project depending on the specifics.

Now you can rerun gradle bloopInstall to have a properly configured SemanticDB plugin in Bloop config.

This is much more complex than in case of the automatic installation, so it is recommended to only do manual installation when having problems with the automatic one. You can also always try to reach us on the Metals gitter channel in case of any problems.

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