Indent multiline expression

CHANGELOG.md

@@ -232,6 +232,7 @@ Previously the default value for `.editorconfig` property `max_line_length` was
 * Wrap the type or value of a property in case the maximum line length is exceeded `property-wrapping` ([#1846](https://github.com/pinterest/ktlint/pull/1846))
 * Recognize Kotlin Script when linting and formatting code from `stdin` with KtLint CLI ([#1832](https://github.com/pinterest/ktlint/issues/1832))
 * Add new experimental rule `no-blank-line-in-list` for `ktlint_official` code style. This rule disallows blank lines to be used in super type lists, type argument lists, type constraint lists, type parameter lists, value argument lists, and value parameter lists. This rule can also be run for other code styles but then its needs to be explicitly enabled. ([#1224](https://github.com/pinterest/ktlint/issues/1224))
+* Add new experimental rule `multiline-expression-wrapping` for `ktlint_official` code style. This forces a multiline expression as value in an assignment to start on a separate line. This rule can also be run for other code styles but then its needs to be explicitly enabled. ([#1217](https://github.com/pinterest/ktlint/issues/1217))
 
 ### Removed
 
@@ -260,6 +261,7 @@ Previously the default value for `.editorconfig` property `max_line_length` was
 * When negate-patterns only are specified in Ktlint CLI then automatically add the default include patterns (`**/*.kt` and `**/*.kts`) so that all Kotlin files excluding the files matching the negate-patterns will be processed ([#1847](https://github.com/pinterest/ktlint/issues/1847))
 * Do not remove newlines from multiline type parameter lists `type-parameter-list-spacing` ([#1867](https://github.com/pinterest/ktlint/issues/1867))
 * Wrap each type parameter in a multiline type parameter list `wrapping` ([#1867](https://github.com/pinterest/ktlint/issues/1867))
+* Allow value arguments with a multiline expression to be indented on a separate line `indent` ([#1217](https://github.com/pinterest/ktlint/issues/1217))
 
 ### Changed
 * Wrap the parameters of a function literal containing a multiline parameter list (only in `ktlint_official` code style) `parameter-list-wrapping` ([#1681](https://github.com/pinterest/ktlint/issues/1681)).

docs/rules/experimental.md

@@ -482,3 +482,34 @@ Rule id: `context-receiver-wrapping`
 A KDoc comment should start and end on a line that does not contain any other element.
 
 Rule id: `kdoc-wrapping`
+
+### Multiline expression wrapping
+
+Multiline expression on the right hand side of an expression are forced to start on a separate line. Expressions in return statement are excluded as that would result in a compilation error. 
+
+=== "[:material-heart:](#) Ktlint"
+
+    ```kotlin
+    val foo =
+        foo(
+            parameterName =
+                "The quick brown fox "
+                    .plus("jumps ")
+                    .plus("over the lazy dog"),
+        )
+    ```
+
+=== "[:material-heart-off-outline:](#) Disallowed"
+
+    ```kotlin
+    val foo = foo(
+        parameterName = "The quick brown fox "
+            .plus("jumps ")
+            .plus("over the lazy dog"),
+    )
+    ```
+
+Rule id: `multiline-expression-wrapping`
+
+!!! Note
+    This rule is only run when `ktlint_code_style` is set to `ktlint_official` or when the rule is enabled explicitly.

ktlint-api-consumer/src/main/kotlin/com/example/ktlint/api/consumer/KtlintApiConsumer.kt

@@ -11,17 +11,19 @@ private val LOGGER = KotlinLogging.logger {}.initKtLintKLogger()
 
 public class KtlintApiConsumer {
     // The KtLint RuleEngine only needs to be instantiated once and can be reused in multiple invocations
-    private val ktLintRuleEngine = KtLintRuleEngine(
-        ruleProviders = KTLINT_API_CONSUMER_RULE_PROVIDERS,
-    )
+    private val ktLintRuleEngine =
+        KtLintRuleEngine(
+            ruleProviders = KTLINT_API_CONSUMER_RULE_PROVIDERS,
+        )
 
     public fun run(
         command: String,
         fileName: String,
     ) {
-        val codeFile = Code.fromFile(
-            File(fileName),
-        )
+        val codeFile =
+            Code.fromFile(
+                File(fileName),
+            )
 
         when (command) {
             "lint" -> {

ktlint-api-consumer/src/main/kotlin/com/example/ktlint/api/consumer/rules/CustomRuleSetProvider.kt

@@ -5,9 +5,10 @@ import com.pinterest.ktlint.ruleset.standard.rules.IndentationRule
 
 internal val CUSTOM_RULE_SET_ID = "custom-rule-set-id"
 
-internal val KTLINT_API_CONSUMER_RULE_PROVIDERS = setOf(
-    // Can provide custom rules
-    RuleProvider { NoVarRule() },
-    // but also reuse rules from KtLint rulesets
-    RuleProvider { IndentationRule() },
-)
+internal val KTLINT_API_CONSUMER_RULE_PROVIDERS =
+    setOf(
+        // Can provide custom rules
+        RuleProvider { NoVarRule() },
+        // but also reuse rules from KtLint rulesets
+        RuleProvider { IndentationRule() },
+    )