Default (and sane) configurations for Scalafmt

Installation

Add the following line to your plugins.sbt file:

addSbtPlugin("com.alejandrohdezma" % "sbt-scalafmt-defaults" % "0.9.1")

You'll also need to provide the sbt-scalafmt plugin.

Usage

The included plugin is automatically activated. It will create a .scalafmt.conf in your project's root folder with the following content:

# This file has been automatically generated and should
# not be edited nor added to source control systems.

# To edit the original configurations go to
# https://github.com/alejandrohdezma/sbt-scalafmt-defaults/edit/master/.scalafmt.conf

version = "3.8.3"

# This value is automatically set based on your current `ThisBuild / scalaVersion` setting.
# `scala212source3`/`scala213source3` will be set if `scalaVersion` is set to any of those versions
#  and `-Xsource:3` option is present under `ThisBuild / scalacOptions`.
runner.dialect = scala212

# Number of maximum characters in a column
maxColumn = 120

# Ensure newlines are added arround top level body definitions always
newlines.topLevelBodyIfMinStatements = [before,after]
newlines.topLevelBodyMinStatements = 1

# Allow line-overflow for comments and lines that would overflow even with a newline.
newlines.avoidForSimpleOverflow=[slc, tooLong]

# Ensure newlines around every statement except `case object` definitions
newlines.topLevelStatementBlankLines = [
  {
    blanks = 1,
    minBreaks = 0,
    regex = "^(?!((Term\.Apply)|(Defn\.Object)))"
  }
]

# Ensure lines starting with the margin character `|` are indented differently
assumeStandardLibraryStripMargin = true

# Align everything that can be aligned
align.preset = most
align.multiline = false
align.tokens."+" = [
  {
    code = ":=", owner = "Term.ApplyInfix"
  },
  {
    code = "+=", owner = "Term.ApplyInfix"
  },
  {
    code = "++=", owner = "Term.ApplyInfix"
  },
  {
    code = "--=", owner = "Term.ApplyInfix"
  },
  {
    code = "-=", owner = "Term.ApplyInfix"
  }
]

# Allow literal argument lists with newlines only once `maxColumn` is reached
binPack.literalArgumentLists = true
binPack.literalsIncludeSimpleExpr = true
binPack.literalsExclude = [ "Term.Name" ]

# Use ScalaDoc style and enable wrapping when reaching `maxColumn`
docstrings.style = "SpaceAsterisk"
docstrings.wrap = yes
docstrings.oneline = fold

rewrite.rules = [
  AvoidInfix, # Avoid infix calls (except for operators)
  RedundantBraces,
  RedundantParens, # Ensure redundant parentheses are removed
  SortModifiers, # Ensure modifiers like `implicit` or `final` are sorted the same
  PreferCurlyFors, # Replaces parentheses into curly braces in for comprehensions that contain multiple enumerator generators
  Imports
]

# Ensure redundant braces are removed
rewrite.redundantBraces.maxLines = 1
rewrite.redundantBraces.stringInterpolation = true

# Ensure a separate line is created for each selector within a `{...}` import.
rewrite.imports.expand = true

# Avoid ASCII tokens
rewriteTokens = {
  "⇒": "=>"
  "→": "->"
  "←": "<-"
}

# Select followed by curly braces should not start a chain
includeCurlyBraceInSelectChains = false

# Ensure code blocks inside markdown files get formated too
project.includePaths = ["glob:**.scala", "glob:**.sbt", "glob:**.sc", "glob:**.md"]
project.excludePaths = ["glob:**metals.sbt"]

You can add the .scalafmt.conf file to the repository's .gitignore, since it's going to be automatically re-created on every build.

Runner-dialect

Since v3.1.0, the Scalafmt runner.dialect option is mandatory. This plugin automatically sets this option based on your current ThisBuild / scalaVersion setting. The scala212source3/scala213source3 will be set if scalaVersion is set to those and -Xsource:3 option is present under ThisBuild / scalacOptions.

If for any reason you want to alter the generated dialect or specify the runner.dialect for a subset of files using fileOverride you can use the .scalafmt-extra.conf file.

Extra configurations

Extra configurations can be added to a file named .scalafmt-extra.conf at the root of your repository. The content of this file will be automatically appended to the auto-generated .scalafmt.conf.