Add option to merge no expect-actual declarations

plugins/base/src/main/kotlin/DokkaBaseConfiguration.kt

@@ -8,12 +8,14 @@ data class DokkaBaseConfiguration(
     var customStyleSheets: List<File> = defaultCustomStyleSheets,
     var customAssets: List<File> = defaultCustomAssets,
     var separateInheritedMembers: Boolean = separateInheritedMembersDefault,
-    var footerMessage: String = defaultFooterMessage
+    var footerMessage: String = defaultFooterMessage,
+    var mergeNoExpectActualDeclarations: Boolean = mergeNoExpectActualDeclarationsDefault
 ) : ConfigurableBlock {
     companion object {
         val defaultFooterMessage = "© ${Year.now().value} Copyright"
         val defaultCustomStyleSheets: List<File> = emptyList()
         val defaultCustomAssets: List<File> = emptyList()
         const val separateInheritedMembersDefault: Boolean = false
+        const val mergeNoExpectActualDeclarationsDefault: Boolean = false
     }
 }

plugins/base/src/main/kotlin/transformers/pages/merger/SameMethodNamePageMergerStrategy.kt

@@ -37,9 +37,9 @@ class SameMethodNamePageMergerStrategy(val logger: DokkaLogger) : PageMergerStra
             .reduce { acc, node ->
                 acc.mapTransform<ContentDivergentGroup, ContentNode> { g ->
                     g.copy(children = (g.children +
-                            (node.dfs { it is ContentDivergentGroup && it.groupID == g.groupID } as? ContentDivergentGroup)
-                                ?.children?.single()
-                            ).filterNotNull()
+                            ((node.dfs { it is ContentDivergentGroup && it.groupID == g.groupID } as? ContentDivergentGroup)
+                                ?.children ?: emptyList())
+                            )
                     )
                 }
             }