KtLint configuration
Ktlint uses a limited set of .editorconfig
properties for additional configuration. A sensible default value is provided for each property when not explicitly defined. Properties can be overridden, provided they are specified under [*.{kt,kts}]
. Ktlint uses some properties defined by .editorconfig, IntelliJ IDEA and custom properties.
Danger
Unfortunately IntelliJ IDEA has an autoformat issue regarding .editorconfig
. Due to this error an additional space is added between glob statements, resulting in [*{kt, kts}]
instead of [*{kt,kts}]
. The .editorconfig
library used by ktlint
ignores sections after encountering a space in the list. As a result, the rule is not applied on all files as documented in the original ktlint issue.
Code style¶
By default, the offical
Kotlin code style is applied. Alternatively, the code style can be set to android
.
Disabled rules¶
By default, no rules are disabled. The property disabled_rules
holds a comma separated list (without spaces). Rules which are not defined in the standard
ruleset have to be prefixed. Rules defined in the standard
ruleset may optionally be prefixed.
Example:
[*.{kt,kts}]
disabled_rules = some-standard-rule,experimental:some-experimental-rule,my-custom-ruleset:my-custom-rule
Final newline¶
By default, a final newline is required at the end of the file.
This setting only takes effect when rule final-newline
is enabled.
Force multiline function signature based on number of parameters¶
By default, the number of parameters in a function signature is not relevant when rewriting the function signature. Only the maximum line length determines when a function signature should be written on a single line or with multiple lines. Setting ktlint_function_signature_rule_force_multiline_when_parameter_count_greater_or_equal_than
can be used, to force a multiline function signature in case the function contain at least a number of parameters even in case the function signature would fit on a single line. Use value -1
(default) to disable this setting.
[*.{kt,kts}]
ktlint_function_signature_rule_force_multiline_when_parameter_count_greater_or_equal_than= -1
This setting only takes effect when rule experimental:function-signature
is enabled.
Wrapping the expression body of a function¶
Setting ktlint_function_signature_body_expression_wrapping
determines if and when the expression body of a function is wrapped to a new line. This setting can be set to value default
, multiline
or always
.
When set to default
, the first line of a body expression is appended to the function signature as long as the max line length is not exceeded.
// Given that the function signature has to be written as a single line function signature
fun someFunction(a: Any, b: Any): String = "some-result"
.uppercase()
// Given that the function signature has to be written as a multiline function signature
fun someFunction(
a: Any,
b: Any
): String = "some-result"
.uppercase()
When set to multiline
, the body expression starts on a separate line in case it is a multiline expression. A single line body expression is wrapped only when it does not fit on the same line as the function signature.
// Given a single line body expression and
// a the function signature that has to be written as a single line function signature and
// it does not exceed the max line length
fun someFunction(a: Any, b: Any): String = "some-result".uppercase()
// Given a single line body expression and
// a the function signature that has to be written as a multiline function signature and
// it does not exceed the max line length
fun someFunction(
a: Any,
b: Any
): String = "some-result".uppercase()
// Given a single line body expression then always wrap it to a separate line
fun someFunction(a: Any, b: Any): String =
"some-result"
.uppercase()
fun someFunction(
a: Any,
b: Any
): String =
"some-result"
.uppercase()
When set to always
the body expression is always wrapped to a separate line.
fun someFunction(a: Any, b: Any): String =
"some-result".uppercase()
fun functionWithAVeryLongName(
a: Any,
b: Any
): String =
"some-result"
.uppercase()
This setting only takes effect when rule experimental:function-signature
is enabled.
Ignore identifiers enclosed in backticks¶
By default, the identifiers enclosed in backticks are not ignored.
According to Kotlin coding conventions it is acceptable to write method names in natural language. When using natural language, the description tends to be longer. This property allows lines containing an identifier between backticks to be longer than the maximum line length. (Since 0.41.0)
This setting only takes effect when rule max-line-length
is enabled.
Import layouts¶
By default, the same imports are allowed as in IntelliJ IDEA. The import path can be a full path, e.g. "java.util.List." as well as wildcard path, e.g. "kotlin.*".
The layout can be composed by the following symbols:
*
- wildcard. There must be at least one entry of a single wildcard to match all other imports. Matches anything after a specified symbol/import as well.|
- blank line. Supports only single blank lines between imports. No blank line is allowed in the beginning or end of the layout.^
- alias import, e.g. "^android.*" will match all android alias imports, "^" will match all other alias imports.
Examples:
ij_kotlin_imports_layout=* # alphabetical with capital letters before lower case letters (e.g. Z before a), no blank lines
ij_kotlin_imports_layout=*,java.**,javax.**,kotlin.**,^ # default IntelliJ IDEA style, same as alphabetical, but with "java", "javax", "kotlin" and alias imports in the end of the imports list
ij_kotlin_imports_layout=android.**,|,^org.junit.**,kotlin.io.Closeable.*,|,*,^ # custom imports layout
Wildcard imports can be allowed for specific import paths (Comma-separated list, use "**" as wildcard for package and all subpackages). This setting overrides the no-wildcard-imports rule. This setting is best be used for allowing wildcard imports from libraries like Ktor where extension functions are used in a way that creates a lot of imports.
This setting only takes effect when rule no-wildcard-imports
is enabled.
Indent size & style¶
By default, indenting is done with 4 spaces per indent level in official
Kotlin code style while a single tab is used by default in the android
code style.
[*.{kt,kts}]
indent_size = 4 # possible values: number (e.g. 2), "unset" (makes ktlint ignore indentation completely)
indent_style = space # or "tab"
Those settings are used by multiple rules of which rule indent
is the most important.
Max line length¶
By default, the maximum line length is not set. The android
code style sets the max line length to 100 (per Android Kotlin Style Guide).
[*.{kt,kts}]
max_line_length = -1 # Use "off" (or -1) to ignore max line length or a positive number to set max line length
This setting is used by multiple rules of which rule max-line-length
is the most important.
Trailing comma on call site¶
By default, trailing comma's on call site are not allowed. When enabling the property, the trailing comma becomes mandatory where applicable.
Example:
This setting only takes effect when rule trailing-comma-on-call-site
is enabled.
Trailing comma on declaration site¶
By default, trailing comma's on declaration site are not allowed. When enabling the property, the trailing comma becomes mandatory where applicable.
Example:
This setting only takes effect when rule trailing-comma-on-declaration-site
is enabled.
Overriding Editorconfig properties for specific directories¶
You can override properties for specific directories inside your project: