Force blank line before object declaration

CHANGELOG.md

@@ -18,6 +18,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 * Do not force blank line before function in right hand side of assignment `blank-line-before-declaration` [#2260](https://github.com/pinterest/ktlint/issue/2260)
 * Ignore override of function in rule `function-naming` [#2271](https://github.com/pinterest/ktlint/issue/2271)
 * Do not replace function body having a return statement only in case the return statement contains an intermediate exit point 'function-expression-body' [#2269](https://github.com/pinterest/ktlint/issue/2269)
+* Force blank line before object declaration if preceded by another declaration `blank-line-before-declaration` [#2284](https://github.com/pinterest/ktlint/issues/2284)
 
 ### Changed
 

ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/BlankLineBeforeDeclarationRule.kt

@@ -8,6 +8,8 @@ import com.pinterest.ktlint.rule.engine.core.api.ElementType.EQ
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.FUN
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.FUNCTION_LITERAL
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.LBRACE
+import com.pinterest.ktlint.rule.engine.core.api.ElementType.OBJECT_DECLARATION
+import com.pinterest.ktlint.rule.engine.core.api.ElementType.OBJECT_LITERAL
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.PROPERTY
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.PROPERTY_ACCESSOR
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.WHEN
@@ -48,6 +50,7 @@ public class BlankLineBeforeDeclarationRule :
             CLASS,
             CLASS_INITIALIZER,
             FUN,
+            OBJECT_DECLARATION,
             PROPERTY,
             PROPERTY_ACCESSOR,
             ->
@@ -126,6 +129,15 @@ public class BlankLineBeforeDeclarationRule :
             return
         }
 
+        if (node.elementType == OBJECT_DECLARATION && node.treeParent.elementType == OBJECT_LITERAL) {
+            // Allow:
+            //   fun foo() =
+            //      object : Foo() {
+            //          // some declarations
+            //      }
+            return
+        }
+
         node
             .takeIf { it.psi is KtDeclaration }
             ?.takeIf {

ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/BlankLineBeforeDeclarationRuleTest.kt

@@ -3,6 +3,7 @@ package com.pinterest.ktlint.ruleset.standard.rules
 import com.pinterest.ktlint.rule.engine.core.api.editorconfig.CODE_STYLE_PROPERTY
 import com.pinterest.ktlint.rule.engine.core.api.editorconfig.CodeStyleValue
 import com.pinterest.ktlint.test.KtLintAssertThat
+import com.pinterest.ktlint.test.KtlintDocumentationTest
 import com.pinterest.ktlint.test.LintViolation
 import org.junit.jupiter.api.Nested
 import org.junit.jupiter.api.Test
@@ -459,4 +460,43 @@ class BlankLineBeforeDeclarationRuleTest {
             """.trimIndent()
         blankLineBeforeDeclarationRuleAssertThat(code).hasNoLintViolations()
     }
+
+    @KtlintDocumentationTest
+    fun `Issue 2284 - Given an object declaration preceded by another declaration`() {
+        val code =
+            """
+            class C
+            data class DC(val v: Any)
+            interface I
+            object O
+            """.trimIndent()
+        val formattedCode =
+            """
+            class C
+
+            data class DC(val v: Any)
+
+            interface I
+
+            object O
+            """.trimIndent()
+        blankLineBeforeDeclarationRuleAssertThat(code)
+            .hasLintViolations(
+                LintViolation(2, 1, "Expected a blank line for this declaration"),
+                LintViolation(3, 1, "Expected a blank line for this declaration"),
+                LintViolation(4, 1, "Expected a blank line for this declaration"),
+            ).isFormattedAs(formattedCode)
+    }
+
+    @Test
+    fun `Issue 2284 - Given an object declaration wrapped in object literal`() {
+        val code =
+            """
+            fun foo() =
+                object : Foo() {
+                    // some declarations
+                }
+            """.trimIndent()
+        blankLineBeforeDeclarationRuleAssertThat(code).hasNoLintViolations()
+    }
 }