Fix merging of explicit expect/actual with a single callable declaration

dokka-subprojects/plugin-base/src/main/kotlin/org/jetbrains/dokka/base/translators/documentables/DefaultPageCreator.kt

@@ -172,6 +172,13 @@ public open class DefaultPageCreator(
 
     private fun <T : Documentable> List<T>.renameClashingDocumentable(): List<T> =
         groupBy { it.dri }.values.flatMap { elements ->
+            //special case: property and function with the same DRI
+            if(elements.any { it is DProperty } && elements.any { it is DFunction }) {
+                // do not rename [elements] if there is an explicit expect-actual
+                // they should be merged by [SameMethodNamePageMergerStrategy]
+                if(elements.any { it is WithIsExpectActual && it.isExpectActual }) return elements
+            }
+
             if (elements.size == 1) elements else elements.mapNotNull { element ->
                 element.renameClashingDocumentable()
             }

dokka-subprojects/plugin-base/src/test/kotlin/expectActuals/ExpectActualsTest.kt

@@ -509,6 +509,113 @@ class ExpectActualsTest : BaseAbstractTest() {
         }
     }
 
+    @Test
+    fun `should merge an explicit-expectActual property with a single function #3685`() = testInline(
+        """
+        /src/common/test.kt
+        expect class Skiko {
+            val isShowing
+        }
+
+        /src/jvm/test.kt
+        actual class Skiko actual constructor() {
+             actual val isShowing = false
+             fun isShowing(): Boolean {
+                return false
+            }
+        }
+
+        /src/native/test.kt
+        actual class Skiko actual constructor(){
+            actual val isShowing = false
+        }
+        """.trimMargin(),
+        multiplatformConfiguration
+    ) {
+        pagesGenerationStage = { root ->
+            val cl = root.dfs { it.name == "Skiko" && it is ClasslikePageNode } ?: throw IllegalStateException()
+            // before page merging
+            assertEquals(2, cl.children.count { it.name == "isShowing" })
+        }
+       renderingStage = { root, _ ->
+            val documentables = (root.dfs { it.name == "isShowing" } as MemberPageNode).documentables
+           // after page merging
+           assertEquals(listOf(DFunction::class, DProperty::class), documentables.map { it::class })
+        }
+    }
+
+    @Test
+    fun `should merge an explicit-expectActual function with a single property #3685`() = testInline(
+        """
+        /src/common/test.kt
+        expect class Skiko {
+            fun isShowing(): Boolean
+        }
+
+        /src/jvm/test.kt
+        actual class Skiko actual constructor() {
+             val isShowing = false
+             actual fun isShowing(): Boolean {
+                return false
+            }
+        }
+
+        /src/native/test.kt
+        actual class Skiko actual constructor(){
+            actual fun isShowing(): Boolean
+        }
+        """.trimMargin(),
+        multiplatformConfiguration
+    ) {
+        pagesGenerationStage = { root ->
+            val cl = root.dfs { it.name == "Skiko" && it is ClasslikePageNode } ?: throw IllegalStateException()
+            // before page merging
+            assertEquals(2, cl.children.count { it.name == "isShowing" })
+        }
+        renderingStage = { root, _ ->
+            val documentables = (root.dfs { it.name == "isShowing" } as MemberPageNode).documentables
+            // after page merging
+            assertEquals(listOf(DFunction::class, DProperty::class), documentables.map { it::class })
+        }
+    }
+
+    @Test
+    fun `should merge an explicit-expectActual function with a single function #3685`() = testInline(
+        """
+        /src/common/test.kt
+        expect class Skiko {
+            fun isShowing(): Boolean
+        }
+
+        /src/jvm/test.kt
+        actual class Skiko actual constructor() {
+             fun isShowing(b: Boolean): Boolean {
+                return b
+            }
+             actual fun isShowing(): Boolean {
+                return false
+            }
+        }
+
+        /src/native/test.kt
+        actual class Skiko actual constructor(){
+            actual fun isShowing(): Boolean
+        }
+        """.trimMargin(),
+        multiplatformConfiguration
+    ) {
+        pagesGenerationStage = { root ->
+            val cl = root.dfs { it.name == "Skiko" && it is ClasslikePageNode } ?: throw IllegalStateException()
+            // before page merging
+            assertEquals(2, cl.children.count { it.name == "isShowing" })
+        }
+        renderingStage = { root, _ ->
+            val documentables = (root.dfs { it.name == "isShowing" } as MemberPageNode).documentables
+            // after page merging
+            assertEquals(listOf(DFunction::class, DFunction::class), documentables.map { it::class })
+        }
+    }
+
     @Test
     @OnlySymbols("context parameters")
     @OptIn(ExperimentalDokkaApi::class)