Experimental rules

Important

Up and until Ktlint version 0.47, experimental were located in a separate experimental rule set. As of Ktlint version 0.48, each rule set can optionally define experimental rules.

All experimental rules described below are part of the standard rule set of Ktlint. To enable all experimental rules (from all rule sets), set editorconfig property below:

[*.{kt,kts}]
ktlint_experimental=enabled

Also see enable/disable specific rules.

Call expression wrapping

In case a call expression does not fit on the line, the lambda expression, and/or the value argument list after a reference expression are wrapped.

Ktlint Disallowed

// Assume that the last allowed
// character is at the X character
// on the right                  X
val foo1 = bar() {
    "some message"
}
val foo2 = bar(
    "foobarrrrrrrrrrrr"
) { "some message" }
val foo3 = bar(
    "foobarrrrrrrrrrrr"
) {
    "some longgggggggggg message"
}

// Assume that the last allowed
// character is at the X character
// on the right                  X
val foo1 = bar() { "some message" }
val foo2 = bar("foobarrrrrrrrrrrr") { "some message" }
val foo3 = bar("foobarrrrrrrrrrrr") { "some longgggggggggg message" }

Rule id: standard:call-expression-wrapping

Suppress or disable rule (1)

1. Suppress rule in code with annotation below:

   @Suppress("ktlint:standard:call-expression-wrapping")
   

   Enable rule via .editorconfig

   ktlint_standard_call-expression-wrapping = enabled
   

   Disable rule via .editorconfig

   ktlint_standard_call-expression-wrapping = disabled
   

Expression operand wrapping

Wraps each operand in a multiline expression to a separate line.

Ktlint Disallowed

val foo1 = bar || baz
val foo2 =
    bar1 ||
        bar2 ||
        baz1 ||
        (baz2 && baz3)
val foo3 = bar + baz
val foo4 =
    bar1 -
        bar2 -
        baz1 -
        (baz2 * baz3)

val foo =
  multiLineOperand(
      "bar"
  ) || baz
if (bar1 || bar2 ||
    baz1 || (baz2 && baz3)
) {
   // do something
}

Rule id: standard:expression-operand-wrapping

Suppress or disable rule (1)

1. Suppress rule in code with annotation below:

   @Suppress("ktlint:standard:expression-operand-wrapping")
   

   Enable rule via .editorconfig

   ktlint_standard_expression-operand-wrapping = enabled
   

   Disable rule via .editorconfig

   ktlint_standard_expression-operand-wrapping = disabled
   

Lambda return

Do not use a labeled return for the last statement in a lambda.

Ktlint Disallowed

val foo1 = bar { "value" }
val foo2 = bar {
    if (baz()) return@bar "value"

    "value"
}

val foo1 = bar { return@foo "value" }
val foo2 = bar {
    if (baz()) return@bar "value" // This is OK

    return@bar "value" // This is disallowed
}

Rule id: standard:lambda-return

Suppress or disable rule (1)

1. Suppress rule in code with annotation below:

   @Suppress("ktlint:standard:lambda-return")
   

   Enable rule via .editorconfig

   ktlint_standard_lambda-return = enabled
   

   Disable rule via .editorconfig

   ktlint_standard_lambda-return = disabled
   

Package Import Spacing

Enforce one single blank line between package statement and imports

Ktlint Disallowed

package foo

import bar.*

package foo
import bar.*

Rule id: standard:package-import-spacing

Suppress or disable rule (1)

1. Suppress rule in code with annotation below:

   @Suppress("ktlint:package-import-spacing")
   

   Enable rule via .editorconfig

   ktlint_standard_package-import-spacing = enabled
   

   Disable rule via .editorconfig

   ktlint_standard_package-import-spacing = disabled