Scala Linters

Some notes on installing a formatter and code linters for Scala.

[The following are in alphabetical order.]

1. scalafix
2. scalafmt
3. scalastyle
4. wartremover

[I had good success with scalastyle and wartremover but could not get scalafix to work.]

scalafix

Instructions copied from:

https://scalacenter.github.io/scalafix/docs/users/installation

Setup

Add the following to project/plugins.sbt:

addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.5.10")

Add the following to build.sbt:

// These settings must appear after scalacOptions and libraryDependencies.
scalafixSettings
scalafixConfigure(Compile, Test, IntegrationTest)

Verify Setup

To verify the installation, check that scalacOptions and libraryDependencies contain the values below.

[Note that these commands must be typed INSIDE sbt.]

> show scalacOptions
[info] * -Yrangepos                   // required
[info] * -Xplugin-require:semanticdb  // recommended
[info] * -P:semanticdb:sourceroot:/x  // recommended
> show libraryDependencies
[info] * org.scalameta:semanticdb-scalac:2.1.7:plugin->default(compile)

Usage

Just use sbt normally, the run command will trigger scalafix if everything compiles.

scalafmt

[This is a formatter rather than a linter, but still useful.]

Instructions copied from:

http://scalameta.org/scalafmt/#sbt-scalafmt

Setup

Add the following to project/plugins.sbt:

addSbtPlugin("com.geirsson" % "sbt-scalafmt" % "1.4.0")

Usage

Creating a configuration file is optional (the defaults seem fine).

At the command line:

$ sbt scalafmt

Once it completes it will report on the number of files reformatted:

...
[info] Reformatted 3 Scala sources
[success] Total time: 1 s, completed 20-Mar-2018 5:37:27 PM
$

scalastyle

Instructions copied from:

http://www.scalastyle.org/sbt.html

Setup

Add the following to project/plugins.sbt:

addSbtPlugin("org.scalastyle" %% "scalastyle-sbt-plugin" % "1.0.0")

Usage

You will need a configuration file. The easiest way to get one is to use the scalastyleGenerateConfig command (at the command line, NOT inside sbt):

$ sbt scalastyleGenerateConfig

This will create a scalastyle-config.xml in the current directory, with the default settings.

Then you can check your code with the scalastyle command.

At the command line:

$ sbt scalastyle

Or inside sbt:

> scalastyle

This produces a list of errors - broken down by source file - on the console, as well as an XML result file target/scalastyle-result.xml (CheckStyle compatible format).

Some of the warnings may not serve a purpose in a development environment, in which case they can easily be set to false.

wartremover

Instructions copied from:

http://www.wartremover.org/doc/install-setup.html

Setup

Add the following to project/plugins.sbt:

addSbtPlugin("org.wartremover" % "sbt-wartremover" % "2.2.1")

Add the following to build.sbt (at the end seems to work):

wartremoverErrors ++= Warts.unsafe

Usage

Just use sbt normally, the run command will trigger wartremover if everything compiles.

Versions

All versions current as of March, 2018.

To Do

• Add a formatter
• Investigate why scalastyle generates stack traces