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configuration
Configuration

Configuration for scalafmt is defined in a plain text file .scalafmt.conf using HOCON syntax.

Here is an example .scalafmt.conf:

align.preset = more    // For pretty alignment.
maxColumn = 100 // For my wide 30" display.

Most popular

maxColumn

maxColumn
  • Keep in mind that 80 characters fit perfectly on a split laptop screen with regular resolution.
  • GitHub mobile view only shows 80 characters and sometimes you might review code on your phone.
  • Consider refactoring your code before of choosing a value above 100.

assumeStandardLibraryStripMargin

This parameter simply says the .stripMargin method was not redefined by the user to assign special meaning to indentation preceding the | character. Hence, that indentation can be modified.

assumeStandardLibraryStripMargin
align.stripMargin

If true, lines starting with the margin character | (or another if specified in the .stripMargin(...) call) will be indented differently.

If align.stripMargin is true, they will align with the opening triple-quote """ in interpolated and raw string literals. Otherwise, they will be indented relative to the start of the opening line.

assumeStandardLibraryStripMargin = true
align.stripMargin = true
---
val example1 =
  s"""Examples:
  |  * one
  |  * two
  |  * $three
  |""".stripMargin
assumeStandardLibraryStripMargin = true
align.stripMargin = false
---
val example1 =
  s"""|Examples:
      |  * one
      |  * two
      |  * $three
      |""".stripMargin

The pipe character can immediately follow the opening """

assumeStandardLibraryStripMargin = true
align.stripMargin = true
---
val example2 =
  s"""|Examples:
  |  * one
  |  * two
  |  * $three
  |""".stripMargin

Presets

Some sections provide preset values to set multiple parameters at once. These are always accessed via the preset key of the appropriate section, including top-level.

Top-level presets

  • preset=default: this preset is implicit and sets all values to their defaults.
  • preset=IntelliJ: this preset is defined as
    preset = default
    continuationIndent.defnSite = 2
    optIn.configStyleArguments = false
  • preset=defaultWithAlign: this preset is defined as
    preset = default
    align.preset = more
  • preset=Scala.js: this preset is defined as
    preset = default
    binPack.preset = true
    align.ifWhileOpenParen = false
    continuationIndent.callSite = 4
    docstrings.style = Asterisk
    importSelectors = binPack
    newlines {
      neverInResultType = true
      neverBeforeJsNative = true
      sometimesBeforeColonInMethodReturnType = false
    }
    runner.optimizer {
      forceConfigStyleOnOffset = 500
      forceConfigStyleMinArgCount = 5
    }

Indentation

continuationIndent.callSite

continuationIndent.callSite

Example:

continuationIndent.callSite = 2
---
function(
argument1, // indented by 2
""
)

continuationIndent.defnSite

continuationIndent.defnSite

Same as continuationIndent.callSite except for definition site. Example:

continuationIndent.defnSite = 4
---
def function(
argument1: Type1 // indented by 4
): ReturnType

continuationIndent.ctorSite

Since v2.5.0.

Applies to constructors. Defaults to continuationIndent.defnSite.

continuationIndent.ctorSite = 4
continuationIndent.defnSite = 2
---
class A(
 field1: Type1 // indented by 4
) {
 def function2(
  argument1: Type1 // indented by 2
 ): ReturnType = None
}

continuationIndent.extendSite

continuationIndent.extendSite
continuationIndent.withSiteRelativeToExtends
continuationIndent.extendSite = 4
# this one added in v2.5.0
continuationIndent.withSiteRelativeToExtends = 2
maxColumn = 30
---
trait Foo extends A with B with C with D with E {
  def foo: Boolean = true
}

indentOperator

Normally, the first eligible break inside a chain of infix operators is indented by 2.

This group of parameters allows overriding which infix operators are eligible and controls when indentation is omitted.

indentOperator.topLevelOnly

If true, only top-level infix operators are eligible to be exempted from the default indentation rule.

indentOperator.topLevelOnly
indentOperator.topLevelOnly = true
---
function(
  a &&
    b
)
function {
  a &&
    b
}
indentOperator.topLevelOnly = false
---
function(
  a &&
    b
)
function {
  a &&
    b
}

indentOperator.exclude

Defines a regular expression for excluded infix operators. If an eligible operator matches, it will not be indented.

indentOperator.exclude

indentOperator.include

Defines a regular expression for included infix operators. If an eligible operator matches and is not excluded explicitly by indentOperator.exclude, it be will indented.

indentOperator.include

indentOperator.preset

  • default
    • use defaults for all fields
  • spray (also akka)
    • set include = "^.*=$", exclude = "^$"

Alignment

Default: some

Align has several nested fields, which you can customize. However, it comes with four possible presets: none, some, more, & most.

align

align.preset=none

align.preset = none
---
x match { // false for case arrows
  case 2  => 22 // also comments!
  case 22 => 222 // don't align me!
}

Pro tip: Enable this setting to minimize git diffs/conflicts from renamings and other refactorings, without having to ignore whitespace changes in diffs or use --ignore-all-space to avoid conflicts when git merging or rebasing.

Starting with the introduction of align.stripMargin parameter in v2.5.0, one must explicitly enable it to get earlier behaviour of align.preset=none. See assumeStandardLibraryStripMargin.

align.preset=some

align.preset = some
---
x match { // true for case arrows
  case 2 => 22
  case 22 => 222
}

val x = 2 // false for assignment
val xx = 22

case object B extends A // false for `extends`
case object BB extends A

align.preset=more

align.preset = more
---
val x = 2 // true for assignment
val xx = 22

case object B extends A // true for `extends`
case object BB extends A

q -> 22 // true for various infix operators
qq -> 3   // and also comments!

for {
  x <- List(1) // true for alignment enumerator
  yyy <- List(2)
} yield x ** yyy

x match { // true for multiple tokens across multiple lines
  case 1 => 1 -> 2 // first
  case 11 => 11 -> 22 // second

  // A blank line separates alignment blocks.
  case `ignoreMe` => 111 -> 222
}

// Align assignments of similar type.
def name = column[String]("name")
def status = column[Int]("status")
val x = 1
val xx = 22

// Align sbt module IDs.
libraryDependencies ++= Seq(
  "org.scala-lang" % "scala-compiler" % scalaVersion.value,
  "com.lihaoyi" %% "sourcecode" % "0.1.1"
)

align.preset=most

align.preset = most
---
for {
  // align <- with =
  x <- List()
  yyy = 2
  // aligns body by arrow
  zzz <- new Integer {
    def value = 3
  }
} yield x

Note. Only for the truest vertical aligners. Feel free to open PR enabling more crazy vertical alignment here. Expect changes.

align.tokens

Default: [caseArrow]

An align token is a pair of code, which is the string literal of an operator of token, and owner, which is the kind of the closest tree node that owns that token. If no owner is provided, then all tree kinds will be matched.

align.tokens = [{code = "=>", owner = "Case"}]
---
x match {
  case 1 => 1 -> 2
  case 11 => 11 -> 22
}
align.tokens = [
  {code = "%", owner = "Term.ApplyInfix"},
  {code = "%%", owner = "Term.ApplyInfix"}
]
---
val x = List(
"org.scala-lang" %% "scala-compiler" % scalaVersion.value,
"com.lihaoyi" %% "sourcecode" % "0.1.1"
)

To find the owner part for a custom tree, depend on Scalameta and use scala.meta.Tree.productPrefix from the (for example, Ammonite) REPL.

@ import $ivy.`org.scalameta:scalameta_2.12:@SCALAMETA_VERSION@`, scala.meta._
@ val termMatch = q"x match { case 2 => foo(bar) }"
termMatch: Term.Match = x match {
 case 2 =>
   foo(bar)
}
@ termMatch.structure
res0: String = """
Term.Match(Term.Name("x"), Seq(Case(Lit.Int(2), None, Term.Apply(Term.Name("foo"), Seq(Term.Name("bar"))))))
"""

@ termMatch.productPrefix
res1: String = "Term.Match"

align.tokens.add

Usage is identical to align.tokens, but token pairs will be added to defaults rather than replacing them.

align.arrowEnumeratorGenerator

align.arrowEnumeratorGenerator
align.arrowEnumeratorGenerator = false
---
for {
  x <- new Integer {
     def value = 2
     }
} yield x
align.arrowEnumeratorGenerator = true
---
for {
  x <- new Integer {
     def value = 2
     }
} yield x

align.openParenCallSite

align.openParenCallSite

Default changed from true to false in v1.6.

align.openParenCallSite = true
---
foo(arg1, arg2)

function(arg1, // align by (
    arg2,
 arg3)

function(
  argument1,
  argument2)
align.openParenCallSite = false
---
foo(arg1, arg2)

function(arg1, // no align by (
    arg2,
 arg3)

function(
  argument1,
  argument2)

align.openParenDefnSite

align.openParenDefnSite

Default changed from true to false in v1.6.

align.openParenDefnSite = true
---
class IntString(int: Int, string: String)

class IntStringLong(int: Int,
    string: String,
  long: Long)
align.openParenDefnSite = false
---
class IntString(int: Int, string: String)

class IntStringLong(
      int: Int,
    string: String,
  long: Long
)

align.stripMargin

See assumeStandardLibraryStripMargin.

align.stripMargin

This functionality is enabled in all presets except align.preset=none where it was disabled since the parameter's introduction in v2.5.0.

align.multiline

If this flag is set, when alignment is applied, multiline statements will not be excluded from search of tokens to align.

Since v2.5.0.

align.multiline
align.preset = more
align.multiline = true
---
for {
  a <- aaa
  bbb <- bb
  cccccc <- c {
    3
  }
  dd <- ddddd
} yield ()
align.preset = more
align.multiline = false
---
for {
  a <- aaa
  bbb <- bb
  cccccc <- c {
    3
  }
  dd <- ddddd
} yield ()

Newlines

The newlines.* options are used to configure when and where scalafmt should insert newlines.

You might be interested in the Vertical Multiline section.

newlines.source

Since v2.5.0.

This parameter controls the general approach to line breaks, and whether to take into account existing newlines in the source. The default value (if the parameter is not specified) is the classic, original way. Below are the alternatives.

These alternatives are EXPERIMENTAL and might change in the future without regard to any edition settings, until fully released (and this message deleted).

newlines.source=keep

This approach attempts to preserve line breaks in the input whenever possible.

newlines.source=fold,unfold

These two approaches completely ignore existing line breaks, except around comments and blank lines (i.e., multiple consecutive newlines).

Might require increasing runner limits (runner.optimizer.maxVisitsPerToken, possibly even runner.maxStateVisits), to avoid SearchStateExploded exceptions.

fold attempts to remove line breaks whenever possible resulting in a more horizontal, or vertically compact look.

unfold, on the other hand, is intended for those who prefer a more vertical, or horizontally compact look.

Both settings attempt to play nice with other parameters, but some combinations are prohibited and will result in an error.

Config-style formatting

This formatting applies to argument lists in class definitions and method calls. It normally involves a newline after the opening parenthesis (or after the implicit keyword) and a newline before the closing parenthesis.

As part of the formatting output, arguments are output one per line (but this is not used in determining whether the source uses config-style formatting).

While this parameter is not technically under the newlines section, it logically belongs there.

optIn.configStyleArguments

If true, applies config-style formatting:

  • if single-line formatting is impossible
  • if the source uses config-style and newlines.source = classic/keep
  • if other parameters force config-style (see below)
optIn.configStyleArguments
optIn.configStyleArguments = true
maxColumn=45
---
object a {
  // keeps single line
  def method1(a: Int, b: String): Boolean

  // forces config style
  def method2(a: Int, b: String, c: String): Boolean

  // preserves config style
  def method3(
    a: Int, b: String, c: String
  ): Boolean
}

Forcing config style

Controls parameters which trigger forced config-style formatting. All conditions must be satisfied in order for this rule to apply.

runner.optimizer.forceConfigStyleOnOffset
runner.optimizer.forceConfigStyleMinArgCount
  • runner.optimizer.forceConfigStyleOnOffset: applies to method calls; if positive, specifies the minimum character distance between the matching parentheses, excluding any whitespace
  • runner.optimizer.forceConfigStyleMinArgCount applies to method calls; specifies the minimum number of arguments
optIn.configStyleArguments = true
runner.optimizer.forceConfigStyleOnOffset = 5
runner.optimizer.forceConfigStyleMinArgCount = 2
maxColumn = 60
---
object a {
  // this is a definition, not a method call
  def method(a: String, b: String = null): Boolean

  // keeps single line; min offset not satisfied
  method(a, b)

  // keeps single line; min arg not satisfied
  method(SomeVeryVeryVeryVeryLongArgument)

  // forces config style
  method(foo, bar)
}

danglingParentheses

While this parameter is not technically under the newlines section, it logically belongs there.

danglingParentheses.defnSite

danglingParentheses.defnSite
danglingParentheses.defnSite = true
danglingParentheses.callSite = false
maxColumn=25
---
object a {
  // defnSite
  def method(a: Int, b: String): Boolean

  // callSite
  method(argument1, argument2)
}

danglingParentheses.callSite

danglingParentheses.callSite
danglingParentheses.defnSite = false
danglingParentheses.callSite = true
maxColumn=25
---
object a {
  // defnSite
  def method(a: Int, b: String): Boolean

  // callSite
  method(argument1, argument2)
}

danglingParentheses.ctrlSite

Since v2.5.0.

Forces dangling on open/close parens around control structures (if, while, for) when line breaks must occur.

danglingParentheses.ctrlSite
danglingParentheses.ctrlSite = true
maxColumn=20
---
if (something) {
  // nothing
}
if (something_else) {
  // nothing
}

danglingParentheses.exclude

Since v2.5.0.

When the appropriate danglingParentheses flag (e.g., defnSite) has been set, this parameter can be used to limit contexts where dangling is applied (currently, class, trait and def are supported).

danglingParentheses.exclude
continuationIndent.defnSite = 2
danglingParentheses.defnSite = true
danglingParentheses.exclude = [def]
---
def other(a: String, b: String)(c: String, d: String) = a + b + c
other(a, b)(c, d)

newlines.topLevelStatements

Since v2.5.0.

This parameter, together with its companions below, controls whether to enforce a blank line before and/or after a top-level statement spanning a certain number of lines.

This parameter will not cause any blank lines to be removed.

newlines.topLevelStatements
newlines.topLevelStatements = []
---
import org.scalafmt
package core { // no newline added here
  class C1 {}
  object O { // nor here
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  } // nor here
  class C2 {}
}
newlines.topLevelStatements = [before]
---
import org.scalafmt
package core {
  class C1 {}
  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }
  class C2 {}
}
newlines.topLevelStatements = [after]
---
import org.scalafmt
package core {
  class C1 {}
  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }
  class C2 {}
}
newlines.topLevelStatements = [before,after]
---
import org.scalafmt
package core {
  class C1 {}
  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }
  class C2 {}
}

newlines.topLevelStatementsMinBreaks

Since v2.5.0.

This parameter sets the minimum of line breaks between the first and last line of a top-level statement (i.e., one less than the number of lines the statement spans). For instance, newlines.topLevelStatementsMinBreaks=0 will apply to all top-level statements, whereas 1 will require at least one line break (or a multi-line statement).

newlines.topLevelStatementsMinBreaks
newlines.topLevelStatements = [before,after]
newlines.topLevelStatementsMinBreaks = 0
---
package core {
  object O {
    val x1 = 1
    val x2 = 2
    def A =
      "A"
    def B = {
      "B"
    }
  }
}
newlines.topLevelStatements = [before,after]
newlines.topLevelStatementsMinBreaks = 2
---
import org.scalafmt
package core {
  object O {
    val x1 = 1
    val x2 = 2
    def A =
      "A"
    def B = {
      "B"
    }
  }
}

newlines.beforeMultiline

Since 2.7.0

This parameter controls whether to force a new line before a multi-line body of case/if/val and how to format it if the space is allowed. (For multi-line bodies of method definitions, please see newlines.beforeMultilineDef below.)

It accepts the same values as newlines.source (and defaults to that parameter's setting).

NB: for breaks before parameters of a multi-line lambda, use multiline with newlines.beforeCurlyLambdaParams.

newlines.beforeMultiline = unfold
---
a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}
newlines.beforeMultiline = fold
---
a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}
newlines.beforeMultiline = keep
---
a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}
# newlines.beforeMultiline = classic
---
a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

newlines.beforeMultilineDef

Since 2.7.0

This parameter applies to multi-line definitions only. It accepts the same values as newlines.beforeMultiline (and defaults to that parameter's setting).

It replaced deprecated boolean newlines.alwaysBeforeMultilineDef (with false mapped to fold and true to unfold).

newlines.beforeMultilineDef = unfold
---
// had space after "="
def foo: String = "123".map { x =>
  x.toUpper
}
// had newline after "="
def foo: String =
  "123".map { x =>
    x.toUpper
  }
newlines.beforeMultilineDef = fold
---
// had space after "="
def foo: String = "123".map { x =>
  x.toUpper
}
// had newline after "="
def foo: String =
  "123".map { x =>
    x.toUpper
  }
newlines.beforeMultilineDef = keep
---
// had space after "="
def foo: String = "123".map { x =>
  x.toUpper
}
// had newline after "="
def foo: String =
  "123".map { x =>
    x.toUpper
  }
# newlines.beforeMultilineDef = classic
---
// had space after "="
def foo: String = "123".map { x =>
  x.toUpper
}
// had newline after "="
def foo: String =
  "123".map { x =>
    x.toUpper
  }

newlines.alwaysBeforeElseAfterCurlyIf

newlines.alwaysBeforeElseAfterCurlyIf
newlines.alwaysBeforeElseAfterCurlyIf = true
---
if (someCond) {
  foo()
} else {
  bar()
}
newlines.alwaysBeforeElseAfterCurlyIf = false
---
if (someCond) {
  foo()
}
else {
  bar()
}

newlines.beforeCurlyLambdaParams

This parameter controls whether a newline is forced between the opening curly brace and the parameters of a lambda or partial function. Added in 2.7.0, replacing boolean alwaysBeforeCurlyBraceLambdaParams.

newlines.beforeCurlyLambdaParams
newlines.beforeCurlyLambdaParams = never
---
// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break on arrow since case doesn't fit on a line
x.zipWithIndex.map { case (c, i) => s"$c -> $i" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }
newlines.beforeCurlyLambdaParams = always
---
// should break on brace, though fits on the same line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2} (long comment)" }
newlines.beforeCurlyLambdaParams = multiline
---
// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break on brace as lambda doesn't fit on the same line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2}" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i" }
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2} (long comment)" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }
newlines.beforeCurlyLambdaParams = multilineWithCaseOnly
---
// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break after arrow as lambda doesn't fit on the same line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2}" }
x.zipWithIndex.map { x => s"${x._1} -> ${x._2} (long comment)" }
// should break on brace as lambda doesn't fit on the same line
x.zipWithIndex.map { case (c, i) => s"$c -> $i" }
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }

newlines.afterCurlyLambdaParams

This parameter controls handling of newlines after the arrow following the parameters of a curly brace lambda or partial function, and whether a space can be used for one-line formatting of the entire function body (if allowed but the body doesn't fit, a break is always forced).

This parameter was renamed in 2.7.0 from afterCurlyLambda, for clarity and consistency with beforeCurlyLambdaParams defined above.

newlines.afterCurlyLambdaParams
newlines.afterCurlyLambdaParams = squash
---
// remove all blank lines if any
// one-line formatting is allowed
something.map { x =>



  f(x)
}

something.map { x => f(x) }
newlines.afterCurlyLambdaParams = never
---
// remove all blank lines if any
// one-line formatting depends on newlines.source:
// yes for fold; no for unfold; otherwise, only if there was no break
something.map { x =>



  f(x)
}

something.map { x => f(x) }
newlines.afterCurlyLambdaParams = preserve
---
// if blank lines are present, keep only one
// one-line formatting depends on newlines.source:
// yes for fold; no for unfold; otherwise, only if there was no break
something.map { x =>



  f(x)
}

something.map { x => f(x) }
newlines.afterCurlyLambdaParams = always
---
// ensure a single blank line
// one-line formatting is not allowed
something.map { x =>



  f(x)
}

something.map { x => f(x) }

Newlines around implicit parameter list modifier

Since v2.5.0.

Newlines around using parameter and argument list modifier

Since v3.0.0

using soft keyword was introduced in Scala 3 and is supported in scalafmt. The settings newlines.implicitParamListModifierPrefer and newlines.implicitParamListModifierForce are from now on aliases for newlines.usingParamListModifierPrefer and newlines.usingParamListModifierForce. By picking one of them formatting will be applied at the same time to both implicit and using. Besides parameter lists, using can also be used with argument lists hence provided rules will then also be applied to the argument lists.

Prefer After (default)

Prefers newline after implicit. Newline will be added unless the entire implicit parameter list fits on a line, or config style is false. Newline can also be added before if the keyword itself would overflow the line.

maxColumn = 60
newlines.implicitParamListModifierPrefer = after
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Prefer Before

Prefers newline before implicit. Newline will not be added if the entire implicit parameter list fits on a line.

maxColumn = 60
newlines.implicitParamListModifierPrefer = before
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Force Before

If set, forces newline before implicit. Otherwise, newline can still be added if the keyword would overflow the line.

maxColumn = 60
newlines.implicitParamListModifierForce = [before]
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Force After

If set, forces newline after implicit. Otherwise, newline can still be added unless before is true, or the entire implicit parameter list fits on a line, or config style is false.

maxColumn = 60
newlines.implicitParamListModifierForce = [after]
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Force both before and after

maxColumn = 60
newlines.implicitParamListModifierForce = [before,after]
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Implicit with optIn.configStyleArguments

While config-style normally requires a newline after the opening parenthesis, postponing that break until after the implicit keyword is allowed if other parameters require keeping this keyword attached to the opening brace.

Therefore, any of the parameters described in this section will take precedence even when optIn.configStyleArguments = true is used.

newlines.afterInfix

Since v2.5.0.

This parameter (and its companions) controls formatting around infix expressions.

The default value depends on newlines.source (see below).

newlines.afterInfix=keep

This approach preserves line breaks in the input. This is the original behaviour, and default for newlines.source=classic,keep.

newlines.afterInfix=many,some

These approaches completely ignore existing newlines around infix, always use a space before an infix operator and occasionally break after it. some is default for newlines.source=fold, and many for newlines.source=unfold.

Might require increasing runner limits (runner.optimizer.maxVisitsPerToken, possibly even runner.maxStateVisits), to avoid SearchStateExploded exceptions.

some will introduce fewer line breaks than many. Both will attempt to break after higher-precedence operators, and both will always break before an expression enclosed in matching parentheses.

newlines.afterInfixMaxCountPerFile

newlines.afterInfixMaxCountPerFile

If the total number of infix operations in the entire file exceeds newlines.afterInfixMaxCountPerFile, the formatter automatically switches to newlines.afterInfix=keep for this file.

newlines.afterInfixMaxCountPerExprForSome

newlines.afterInfixMaxCountPerExprForSome

If newlines.afterInfix is set to some and the number of infix operations in a given expression sequence (top-level or enclosed in parens/braces) exceeds newlines.afterInfixMaxCountPerExprForSome, the formatter switches to many for that sequence only.

newlines.afterInfixBreakOnNested

newlines.afterInfixBreakOnNested

If enabled, will force line breaks around a nested parenthesized sub-expression in a multi-line infix expression.

newlines.avoidForSimpleOverflow

A list parameter (of comma-separated flags), with possible flags described below. These flags relax formatting rules to allow occasional line overflow (i.e., when line exceeds maxColumn) in simple cases instead of introducing a newline.

newlines.avoidForSimpleOverflow

newlines.avoidForSimpleOverflow=[tooLong]

Since v2.6.0.

This flag tries to avoid introducing a newline if the line would overflow even with a newline.

maxColumn = 50
danglingParentheses.callSite = false
newlines.avoidForSimpleOverflow = [tooLong]
---
object Example {
  foo_bar_baz("the quick brown fox jumps over the lazy dog") {
    println("")
  }
  foo_bar_baz("the quick brown fox jumps over a dog") {
    println("")
  }
}

newlines.avoidForSimpleOverflow=[punct]

Since v2.6.0.

This flag tries to avoid a newline if the line would overflow only because of trailing punctuation (non-alphanum symbols of length 1).

With the flag set:

maxColumn = 80
newlines.avoidForSimpleOverflow = [punct]
---
class Engine[TD, EI, PD, Q, P, A](
    val dataSourceClassMap: Map[
      String,
      Class[_ <: BaseDataSource[TD, EI, Q, A]]]) {}

newlines.avoidInResultType

If true, newlines in definition result type will only be used if formatting without them is impossible. This parameter was added in 2.7.0, replacing neverInResultType.

newlines.avoidInResultType
maxColumn = 40
newlines.avoidInResultType = true
newlines.neverBeforeJsNative = true
---
// no newlines in result type
def permissionState(a: A = js.native): js.Promise[PushPermissionState] = js.native
// no newlines in result type
val permissionState: js.Promise[PushPermissionState] = js.native
// can't format without newlines
implicit protected val td: TildeArrow {
  type Out = RouteTestResult } = TildeArrow.injectIntoRoute

Rewrite Rules

To enable a rewrite rule, add it to the config like this rewrite.rules = [SortImports].

AvoidInfix

rewrite.rules = [AvoidInfix]
---
a success b
a error (b, c)
a map { x =>
  x + 2
}
"o" % "a" % "v" c(D)
future recover {
  case e: Err => 0
} map (_.toString)

ExpandImportSelectors

rewrite.rules = [ExpandImportSelectors]
---
import a.{
    b,
    c
  }, h.{
    k, l
  }
import d.e.{f, g}
import a.{
    foo => bar,
    zzzz => _,
    _
  }

RedundantBraces

Warning. This rewrite can cause non-idempotent formatting, see #1055.

rewrite.rules = [RedundantBraces]
---
def foo = {
  List(1, 2, 3).sum
}
rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.stringInterpolation = true
---
q"Hello ${name}"
rewrite.rules = [RedundantBraces]
---
List(1, 2, 3).map { x => x + 1 }

Entire power of RedundantBraces can be accessed with newlines.afterCurlyLambdaParams=squash. It will try to squash lambda body in one line and then replace braces with parens:

rewrite.rules = [RedundantBraces]
newlines.afterCurlyLambdaParams=squash
---
List(1, 2, 3).map { x =>
  x + 1
}

List(1, 2, 3).map { x =>
  println("you can't squash me!")
  x + 1
}

Configuration options

rewrite.redundantBraces.generalExpressions
rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.generalExpressions = true
---

while (x < 10) {
  x += 1
}

str match {
  case "a" => {
    println("ok")
  }
  case _ => {
    println("not ok")
  }
}
rewrite.redundantBraces.ifElseExpressions
rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.ifElseExpressions = true
---

if (a > b) {
  doSomething()
} else {
  doAnything()
}
rewrite.redundantBraces.methodBodies
rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.methodBodies = true
---
def f() = {
  1 + 1
}
rewrite.redundantBraces.includeUnitMethods

Affects only functions with explicitly specified Unit type

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.methodBodies = true
rewrite.redundantBraces.includeUnitMethods = false
---
def f() = {
  1 + 1
}

def x(): Unit = {
  println("example")
}
rewrite.redundantBraces.stringInterpolation
rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.stringInterpolation = true
---
s"user id is ${id}"

rewrite.redundantBraces.parensForOneLineApply is true by default for edition >= 2020-01. See also newlines.afterCurlyLambdaParams = squash.

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.parensForOneLineApply = true
---
xs.map { x => x + 1 }
rewrite.redundantBraces.maxLines
rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.maxLines = 3
---
def f() = {
  collection
    .map(x => x + 1)
    .filter(_ < 10)
    .map(_ * 2)
}

def f() = {
  collection
    .map(x => x + 1)
    .filter(_ < 10)
    .map(_ * 2)
    .headOption
}

RedundantParens

rewrite.rules = [RedundantParens]
---
for {
  a <- b
  if (a.nonEmpty)
} yield a

val z = (insertData *> readDatabase(id))

SortModifiers

Modifiers are sorted based on the given order. Affects modifiers of the following definitions: trait, class, object, type, and val+var, both as fields and class parameters.

rewrite.rules = [SortModifiers]
---
final lazy private implicit val x = 42
lazy final implicit private val y = 42
rewrite.rules = [SortModifiers]
---
class Test(
    implicit
    final private val i1: Int,
    private final val i2: String
)
rewrite.rules = [SortModifiers]
---
sealed protected[X] trait ADT
final private case object A1 extends ADT
private final case class A2(a: Int)
    extends ADT

If you choose the non-default sort order then you have to specify all eight modifiers in the order you wish to see them. Hint: since some modifiers are mutually exclusive, you might want to order them next to each other.

rewrite.rules = [SortModifiers]
rewrite.sortModifiers.order = [
  "implicit", "final", "sealed", "abstract",
  "override", "private", "protected", "lazy"
]
---
override implicit final val x = 2

PreferCurlyFors

Replaces parentheses into curly braces in for comprehensions that contain multiple enumerator generators.

rewrite.rules = [PreferCurlyFors]
---
for(a <- as; b <- bs if b > 2)
 yield (a, b)

SortImports

The imports are sorted by the groups: symbols, lower-case, upper-case.

rewrite.rules = [SortImports]
---
import foo.{Zilch, bar, Random, sand}

AsciiSortImports

The imports are sorted by their Ascii codes

rewrite.rules = [AsciiSortImports]
---
import foo.{~>, `symbol`, bar, Random}

Trailing commas

See SIP

The rule handles how trailing commas are treated in case of a dangling closing delimiter (parenthesis or bracket for definitions or invocations, brace for import statements only).

Regardless of the setting, trailing commas are always removed if the closing delimiter is not dangling (i.e., follows the final argument without a line break).

This logic is not triggered via the rewrite.rules parameter, but by setting trailingCommas.

trailingCommas

Trailing commas: never

Makes sure there are no trailing commas:

trailingCommas = never
---
import a.{
  b,
  c,
}
def method1(
  a: Int,
  b: Long,
) = {}
def method2(
  a: Int,
  b: Long*,
) = {}
def method3(
  a: Int,
) = {}
method1(
  a,
  b,
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

Trailing commas: preserve

Keeps any trailing commas:

trailingCommas = preserve
---
import a.{
  b,
  c,
}
def method1(
  a: Int,
  b: Long,
) = {}
def method2(
  a: Int,
  b: Long*
) = {}
def method3(
  a: Int,
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

Trailing commas: always

Makes sure there are trailing commas:

trailingCommas = always
---
import a.{
  b,
  c
}
def method1(
  a: Int,
  b: Long
) = {}
def method2(
  a: Int,
  b: Long*
) = {}
def method3(
  a: Int
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*
)
method3(
  a
)

Trailing commas: multiple

Since v2.5.0.

Makes sure there are trailing commas for multiple-argument expressions only, except when the last argument is repeated:

trailingCommas = multiple
---
import a.{
  b,
  c
}
def method1(
  a: Int,
  b: Long
) = {}
def method2(
  a: Int,
  b: Long*,
) = {}
def method3(
  a: Int,
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

Vertical Multiline

Since: v1.6.0.

If enabled this formats methods such that parameters are on their own line indented by continuationIndent.defnSite. Separation between parameter groups are indented by two spaces less than continuationIndent.defnSite. The return type is on its own line at the end.

This formatting is only triggered if the method definition exceeds the maxColumn value in width or if the number of arguments to the method exceeds the verticalMultiline.arityThreshold.

verticalMultiline.arityThreshold

verticalMultiline.arityThreshold
verticalMultiline.atDefnSite = true
verticalMultiline.arityThreshold = 2
---
case class Foo(x: String)
case class Bar(x: String, y: String)
object A {
  def foo(x: String, y: String)
  def hello(how: String)(are: String)(you: String) = how + are + you
}

verticalMultiline.newlineAfterOpenParen

verticalMultiline.newlineAfterOpenParen
continuationIndent.defnSite = 2
verticalMultiline.atDefnSite = true
verticalMultiline.arityThreshold = 2
verticalMultiline.newlineAfterOpenParen = true
---
def other(a: String, b: String)(c: String, d: String) = a + b + c

verticalMultiline.excludeDanglingParens

This parameter has been deprecated, please use danglingParentheses.exclude. Keep in mind, though, that the new parameter is empty by default while the old one isn't, so to use empty exclude list, one must set the old verticalMultiline.excludeDanglingParens=[].

verticalMultiline.excludeDanglingParens
continuationIndent.defnSite = 2
verticalMultiline.excludeDanglingParens = [def]
verticalMultiline.atDefnSite = true
verticalMultiline.arityThreshold = 2
verticalMultiline.newlineAfterOpenParen = true
---
def other(a: String, b: String)(c: String, d: String) = a + b + c
other(a, b)(c, d)

Vertical multiline with implicit parameter lists

Also see the general section on implicit parameter lists.

Before only

maxColumn = 60
verticalMultiline.atDefnSite = true
newlines.implicitParamListModifierForce = [before]
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

After only

maxColumn = 60
verticalMultiline.atDefnSite = true
newlines.implicitParamListModifierForce = [after]
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Before and after

maxColumn = 60
verticalMultiline.atDefnSite = true
newlines.implicitParamListModifierForce = [before,after]
---
def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Comment processing

comments

comments.wrap

Since v2.6.0.

Allows wrapping comments exceeding maxColumn.

comments.wrap
comments.wrap = standalone

A standalone comment is one which is surrounded by line breaks.

maxColumn = 20
comments.wrap = standalone
---
/* long multiline comment */
// long singleline comment
val a = 1 // short
val b = 2 // long singleline comment
comments.wrap = trailing

A trailing comment is one which is followed by a line break.

maxColumn = 20
comments.wrap = trailing
---
/* long multiline comment */
// long singleline comment
val a = 1 // short
val b = 2 // long singleline comment

comments.wrapStandaloneSlcAsSlc

Since v2.6.0.

This parameter allows formatting a standalone single-line comment (i.e., //) to be wrapped using the same type, not a multi-line comment (/* ... */).

comments.wrapStandaloneSlcAsSlc
maxColumn = 20
comments.wrap = trailing
comments.wrapStandaloneSlcAsSlc = true
---
// long singleline comment
val b = 2 // long singleline comment

docstrings

docstrings.style

Since v2.6.0.

docstrings.style
docstrings.style = Preserve

Prohibits formatting of docstrings. All other docstrings parameters are ignored.

docstrings.style = Preserve
---
/**   do not touch
 * this style
  * keep the text as-is
*/
docstrings.style = Asterisk

This variant used to be called JavaDoc.

docstrings.style = Asterisk
---
/** Skip first line, format intermediate lines with an asterisk
  * below the first asterisk of the first line (aka JavaDoc)
  */
docstrings.style = SpaceAsterisk

This variant used to be called ScalaDoc.

docstrings.style = SpaceAsterisk
---
/** Format intermediate lines with a space and an asterisk,
 * both below the two asterisks of the first line
 */
docstrings.style = AsteriskSpace
docstrings.style = AsteriskSpace
---
/** Format intermediate lines with an asterisk and a space,
  * both below the two asterisks of the first line
  */

docstrings.oneline

Since v2.6.0. Ignored for docstrings.style = Preserve.

docstrings.oneline
docstrings.oneline = fold
docstrings.style = Asterisk
docstrings.oneline = fold
---
/** Scaladoc oneline */
/**
  * Scaladoc multiline
  */
val a = 1
docstrings.oneline = unfold
docstrings.style = Asterisk
docstrings.oneline = unfold
---
/** Scaladoc oneline */
/**
  * Scaladoc multiline
  */
val a = 1
docstrings.oneline = keep
docstrings.style = Asterisk
docstrings.oneline = keep
---
/** Scaladoc oneline */
/**
  * Scaladoc multiline
  */
val a = 1

docstrings.wrap

Will parse scaladoc comments and reformat them.

This functionality is generally limited to standard scaladoc elements and might lead to undesirable results in corner cases; for instance, the scaladoc parser doesn't have proper support of embedded HTML.

However, tables are supported.

Since v2.6.0. Ignored for docstrings.style = Preserve.

docstrings.wrap
docstrings.wrap = yes
maxColumn = 30
---
/**
 * @param d the Double to square, meaning multiply by itself
 * @return the result of squaring d
 *
 * Thus
 * - if [[d]] represents a negative value:
 *  a. the result will be positive
 *  a. the value will be {{{d * d}}}
 *  a. it will be the same as for `-d`
 * - however, if [[d]] is positive
 *  - the value will still be {{{d * d}}}
 *    - i.e., the same as {{{(-d) * (-d)}}}
 *
 * In other words:
 * {{{
 *    res = d * d
 *        = (-d) * (-d) }}}
 */
def pow2(d: Double): Double

docstrings.blankFirstLine

Controls whether to force the first line to be blank in a multiline docstring. Keep in mind that some combinations of parameters are prohibited (e.g., blankFirstLine=keep contradicts with style=Asterisk).

Since v2.7.5. Ignored for docstrings.style = Preserve or docstrings.wrap = no.

docstrings.blankFirstLine
# do not force a blank first line
docstrings.blankFirstLine = no
docstrings.style = SpaceAsterisk
maxColumn = 30
---
/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/**
  * Scaladoc multiline2
  */
val a = 1
# force a blank first line
docstrings.blankFirstLine = yes
docstrings.style = SpaceAsterisk
maxColumn = 30
---
/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/**
  * Scaladoc multiline2
  */
val a = 1
# preserve a blank first line
docstrings.blankFirstLine = keep
docstrings.style = SpaceAsterisk
maxColumn = 30
---
/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/**
  * Scaladoc multiline2
  */
val a = 1

Disabling or customizing formatting

For code block

There is a possibility to override scalafmt config for a specific code with // scalafmt: {} comment:

---
// scalafmt: { align.preset = most, danglingParentheses.preset = false }
libraryDependencies ++= Seq(
  "org.scalameta" %% "scalameta" % scalametaV,
  "org.scalacheck" %% "scalacheck" % scalacheckV)

// scalafmt: { align.preset = some, danglingParentheses.preset = true } (back to defaults)
libraryDependencies ++= Seq(
  "org.scalameta" %% "scalameta" % scalametaV,
  "org.scalacheck" %% "scalacheck" % scalacheckV)

// format: off

Disable formatting for specific regions of code by wrapping them in // format: off blocks:

---
// format: off
val identity = Array(1, 0, 0,
                     0, 1, 0,
                     0, 0, 1)
// format: on

Project

Configure which source files should be formatted in this project.

# Only format files tracked by git.
project.git = true
# manually exclude files to format.
project.excludeFilters = [
   regex1
   regex2
]
# manually include files to format.
project.includeFilters = [
  regex1
  regex2
]

fileOverride

Since v2.5.0.

Allows specifying an additional subset of parameters for each file matching a PathMatcher pattern. For instance,

align.preset = none
fileOverride {
  "glob:**/*.sbt" {
    align.preset = most
  }
  "glob:**/src/test/scala/**/*.scala" {
    maxColumn = 120
    binPack.unsafeCallSite = true
  }
}

uses align.preset=none for all files except .sbt for which align.preset=most will apply. It will also use different parameters for test suites.

This parameter does not modify which files are formatted.

Spaces

spaces.beforeContextBoundColon

spaces.beforeContextBoundColon
spaces.beforeContextBoundColon=Never
---
def method[A: Bound]: B
def method[A : Bound]: B
def method[A: Bound: Bound2]: B
spaces.beforeContextBoundColon=Always
---
def method[A: Bound]: B
def method[A : Bound]: B
def method[A: Bound: Bound2]: B
spaces.beforeContextBoundColon=IfMultipleBounds
---
def method[A: Bound]: B
def method[A : Bound]: B
def method[A: Bound: Bound2]: B

spaces.inImportCurlyBraces

spaces.inImportCurlyBraces
spaces.inImportCurlyBraces=true
---
import a.b.{c, d}

spaces.inParentheses

spaces.inParentheses
spaces.inParentheses=true
---
foo(a, b)

spaces.neverAroundInfixTypes

spaces.neverAroundInfixTypes
spaces.neverAroundInfixTypes=["##"]
---
def f: Foo##Repr
def g: Foo\/Repr
// usage same operator not as type
def e = a##b

spaces.afterKeywordBeforeParen

spaces.afterKeywordBeforeParen
spaces.afterKeywordBeforeParen = false
---
if (a) println("HELLO!")
while (a) println("HELLO!")

spaces.inByNameTypes

spaces.inByNameTypes
spaces.inByNameTypes = false
---
def foo(a: => A): A

spaces.afterSymbolicDefs

spaces.afterSymbolicDefs
spaces.afterSymbolicDefs=true
---
def +++(a: A): F[A]

Literals

Since v2.5.0.

Scalafmt allows flexible configuration of Integer and Floating Point literals formatting.

Default formatting:

---
123l
0XFff
0x1Abl
10E-1
10e-1D

Each literals.* setting has three available options: Upper, Lower, Unchanged.

literals.long

literals.long

Responsible for the case of Long literals suffix L

literals.long=Upper
---
123l

literals.float

literals.float

Responsible for the case of Float literals suffix F

literals.float=Lower
---
42.0F

literals.double

literals.double

Responsible for the case of Double literals suffix D

literals.double=Lower
---
42.0d

literals.hexPrefix

literals.hexPrefix

Responsible for the case of hex integer literals prefix 0x

literals.hexPrefix=Lower
---
0X123

literals.hexDigits

literals.hexDigits

Responsible for the case of hex integer literals digits

literals.hexDigits=Lower
literals.long=Upper
---
0xaAaA
0xaAaAl

literals.scientific

literals.scientific

Responsible for the case of Double literals exponent part

literals.scientific=Upper
literals.float=Lower
---
10e-1
10e-1f

XML

Controls formatting of Scala embedded within XML.

xmlLiterals.assumeFormatted

Since v2.6.0.

If set, formats embedded Scala relative to containing XML, making the assumption that XML itself is properly formatted. Otherwise, formatting is relative to the outer Scala code which contains the XML literals.

xmlLiterals.assumeFormatted
maxColumn = 40
xmlLiterals.assumeFormatted = true
---
object Example2 {
  def apply() = {
      <foo>
        <bar>{ (1 + 2 + 3).toString("some long format") }</bar>
      </foo>
  }
}
maxColumn = 40
xmlLiterals.assumeFormatted = false
---
object Example2 {
  def apply() = {
      <foo>
        <bar>{ (1 + 2 + 3).toString("some long format") }</bar>
      </foo>
  }
}

Binpacking

binPack.literalArgumentLists

binPack.literalArgumentLists
binPack.literalArgumentLists = true
---
val secret: List[Bit] = List(0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1,
  0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1)
binPack.literalArgumentLists = false
---
val secret: List[Bit] = List(0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1)
binPack.literalArgumentLists = true
binPack.literalsSingleLine = true
---
val secret: List[Bit] = List(0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1,
  0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1)

See also:

  • binPack.literalsIncludeSimpleExpr (to allow a few select methods followed by a few nested single-argument apply calls, with literals as arguments); added in v2.5.0
  • all other binPack.literalXXX parameters (see list at the bottom) are self-explanatory.

binPack.parentConstructors

Parent constructors are C and D in class A extends B with C and D. Changed from a boolean to a wider set of options in v2.6.0.

binPack.parentConstructors

Keep in mind that explicitly specifying the default value might change behaviour; other parameters, such as newlines.source, could interpret implied default differently but yield to an explicit value.

binPack.parentConstructors = Always
maxColumn = 30
---
object A {
  trait Foo
  extends Bar
  with Baz
}
binPack.parentConstructors = Never
maxColumn = 30
---
object A {
  trait Foo extends Bar with Baz
}
binPack.parentConstructors = Oneline
maxColumn = 30
---
object A {
  class Foo(a: Int)
  extends Bar
  with Baz

  class Foo(
    a: Int
  )
  extends Bar
  with Baz
}
binPack.parentConstructors = OnelineIfPrimaryOneline
maxColumn = 30
---
object A {
  class Foo(a: Int, b: Int)
  extends Bar
  with Baz

  class Foo(
    a: Int,
    b: Int
  ) extends Bar with Baz
}

Classic select chains

The parameters below control formatting of select chains when newlines.source = classic, and specifically which select expressions are included in a chain.

Generally, a chain can either be formatted on one line up to the last select, or will have a break on the first select.

includeCurlyBraceInSelectChains

Controls if select followed by curly braces can start a chain.

includeCurlyBraceInSelectChains
includeCurlyBraceInSelectChains = true
---
List(1).map { x =>
    x + 2
  }
  .filter(_ > 2)
includeCurlyBraceInSelectChains = false
---
List(1)
  .map { x =>
    x + 2
  }
  .filter(_ > 2)

includeNoParensInSelectChains

Controls if select not followed by an apply can start a chain.

includeNoParensInSelectChains
includeNoParensInSelectChains = true
---
List(1).toIterator.buffered
  .map(_ + 2)
  .filter(_ > 2)
includeNoParensInSelectChains = false
---
List(1).toIterator.buffered.map(_ + 2).filter(_ > 2)

optIn.breakChainOnFirstMethodDot

Keeps the break on the first select of the chain if the source contained one. Has no effect if there was no newline in the source.

optIn.breakChainOnFirstMethodDot
optIn.breakChainOnFirstMethodDot = false
---
// collapse into a single line
foo
  .map(_ + 1)
  .filter(_ > 2)
optIn.breakChainOnFirstMethodDot = true
---
// preserve break on first dot and break on subsequent dots
foo
  .map(_ + 1).filter(_ > 2)

optIn.breaksInsideChains

Controls whether to preserve a newline before each subsequent select when the very first one used a line break; that is, this parameter doesn't prohibit single-line formatting even if there are source breaks down the chain.

If false, each subsequent select within the chain will behave exactly like the first, that is, either the entire chain will be formatted on one line, or will contain a break on every select.

If true, preserves existence or lack of breaks on subsequent selects if the first select was formatted with a newline.

optIn.breaksInsideChains
optIn.breaksInsideChains = true
maxColumn = 35
---
foo.bar(_ + 1)
  .baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux(_ * 12)
foo.bar(_ + 1).baz(_ > 2).qux { _ * 12 }
foo.bar(_ + 1)
  .baz(_ > 2).qux(_ * 12)
optIn.breaksInsideChains = false
maxColumn = 35
---
foo.bar(_ + 1)
  .baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux(_ * 12)
foo.bar(_ + 1).baz(_ > 2).qux { _ * 12 }
foo.bar(_ + 1)
  .baz(_ > 2).qux(_ * 12)

optIn.encloseClassicChains

Controls what happens if a chain enclosed in parentheses is followed by additional selects. Those additional selects will be considered part of the enclosed chain if and only if this flag is false.

Since 2.6.2.

optIn.encloseClassicChains
optIn.encloseClassicChains = true
maxColumn = 30
---
(foo.map(_ + 1).map(_ + 1))
  .filter(_ > 2)
optIn.encloseClassicChains = false
maxColumn = 30
---
(foo.map(_ + 1).map(_ + 1))
  .filter(_ > 2)

Scala 3

Scalafmt has basic support for Scala 3 features that can be enabled by changing the dialect of the Scalafmt parser.

runner.dialect = Scala3
---
open class MyOpenClass()
val myQuote = '{ expr }
val mySplice = ${ expr }
enum class Weekday {
  case Monday, Tuesday, Wednesday, Thursday, Friday
}

Miscellaneous

optIn.forceBlankLineBeforeDocstring

If true, always insert a blank line before docstrings;
If false, preserves blank line only if one exists before.

optIn.forceBlankLineBeforeDocstring
optIn.forceBlankLineBeforeDocstring = true
---
object Stuff {
  /** Some function */
  def hello = ()
}
optIn.forceBlankLineBeforeDocstring = false
---
object Stuff {
  /** Some function */
  def hello = ()
}

rewriteTokens

Map of tokens to rewrite. For example, Map("⇒" -> "=>") will rewrite unicode arrows to regular ascii arrows.

rewriteTokens
rewriteTokens = {
  "⇒": "=>"
  "→": "->"
  "←": "<-"
}
---
val tuple = "a" → 1
val lambda = (x: Int) ⇒ x + 1
for {
  a ← Option(1)
  b ← Option(2)
} yield a + b

Edition

Removed in 2.7.0

Editions are no longer used. They were kept for backwards compatibility with old configuration files but new changes to the default Scalafmt formatting behavior will not respect the edition setting.

Other

To find all available configuration options, it's best to browse the source code of Scalafmt. A good place to start is ScalafmtConfig. Observe that this listing below is the top-level, there are more configuration options if you visited nested fields like spaces and newlines.