2 files changed, 121 insertions, 0 deletions
diff --git a/plugins/base/src/main/kotlin/DokkaBase.kt b/plugins/base/src/main/kotlin/DokkaBase.kt
index 648acfbb..b18e2ad5 100644
--- a/plugins/base/src/main/kotlin/DokkaBase.kt
+++ b/plugins/base/src/main/kotlin/DokkaBase.kt
@@ -2,10 +2,15 @@ package org.jetbrains.dokka.base
 
 import org.jetbrains.dokka.CoreExtensions
 import org.jetbrains.dokka.base.transformers.descriptors.DefaultDescriptorToDocumentationTranslator
+import org.jetbrains.dokka.base.transformers.documentables.DefaultDocumentableMerger
 import org.jetbrains.dokka.plugability.DokkaPlugin
 
 class DokkaBase: DokkaPlugin() {
     val defaultDescriptorToDocumentationTranslator by extending(isFallback = true) {
         CoreExtensions.descriptorToDocumentationTranslator providing ::DefaultDescriptorToDocumentationTranslator
     }
+
+    val defaultDocumentableMerger by extending(isFallback = true) {
+        CoreExtensions.documentableMerger with DefaultDocumentableMerger
+    }
 }
 \ No newline at end of file
diff --git a/plugins/base/src/main/kotlin/transformers/documentables/DefaultDocumentableMerger.kt b/plugins/base/src/main/kotlin/transformers/documentables/DefaultDocumentableMerger.kt
new file mode 100644
index 00000000..f2e6f177
--- /dev/null
+++ b/plugins/base/src/main/kotlin/transformers/documentables/DefaultDocumentableMerger.kt
@@ -0,0 +1,116 @@
+package org.jetbrains.dokka.base.transformers.documentables
+
+import org.jetbrains.dokka.model.*
+import org.jetbrains.dokka.model.Enum
+import org.jetbrains.dokka.model.Function
+import org.jetbrains.dokka.plugability.DokkaContext
+import org.jetbrains.dokka.transformers.documentation.DocumentableMerger
+import org.jetbrains.dokka.utilities.pullOutNull
+
+internal object DefaultDocumentableMerger : DocumentableMerger {
+    override fun invoke(modules: Collection<Module>, context: DokkaContext): Module {
+        if (!modules.all { it.name == modules.first().name })
+            context.logger.error("All module names need to be the same")
+        return Module(
+            modules.first().name,
+            merge(
+                modules.flatMap { it.packages },
+                Package::mergeWith
+            )
+        )
+    }
+}
+
+private fun <T : Documentable> merge(elements: List<T>, reducer: (T, T) -> T): List<T> =
+    elements.groupingBy { it.dri }
+        .reduce { _, left, right -> reducer(left, right) }
+        .values.toList()
+
+fun PlatformInfo.mergeWith(other: PlatformInfo?) = BasePlatformInfo(
+    documentationNode,
+    (platformData + (other?.platformData ?: emptyList())).distinct()
+)
+
+fun ClassPlatformInfo.mergeWith(other: ClassPlatformInfo?) = ClassPlatformInfo(
+    info.mergeWith(other?.info),
+    (inherited + (other?.inherited ?: emptyList())).distinct()
+)
+
+fun List<ClassPlatformInfo>.mergeClassPlatformInfo(): List<ClassPlatformInfo> =
+    groupingBy { it.documentationNode.children + it.inherited }.reduce { _, left, right ->
+        left.mergeWith(right)
+    }.values.toList()
+
+fun List<PlatformInfo>.merge(): List<PlatformInfo> =
+    groupingBy { it.documentationNode }.reduce { _, left, right ->
+        left.mergeWith(right)
+    }.values.toList()
+
+fun Function.mergeWith(other: Function): Function = Function(
+    dri,
+    name,
+    returnType,
+    isConstructor,
+    (receiver to other.receiver).pullOutNull()?.let { (f, s) -> f.mergeWith(s) },
+    merge(parameters + other.parameters, Parameter::mergeWith),
+    expected?.mergeWith(other.expected),
+    (actual + other.actual).merge(),
+    visibility = (visibility + other.visibility)
+)
+
+fun Property.mergeWith(other: Property) = Property(
+    dri,
+    name,
+    (receiver to other.receiver).pullOutNull()?.let { (f, s) -> f.mergeWith(s) },
+    expected?.mergeWith(other.expected),
+    (actual + other.actual).merge(),
+    accessors = (this.accessors + other.accessors).distinct(),
+    visibility = (visibility + other.visibility)
+)
+
+fun Classlike.mergeWith(other: Classlike): Classlike = when {
+    this is Class && other is Class -> mergeWith(other)
+    this is Enum && other is Enum -> mergeWith(other)
+    else -> throw IllegalStateException("${this::class.qualifiedName} ${this.name} cannot be merged with ${other::class.qualifiedName} ${other.name}")
+}
+
+fun Class.mergeWith(other: Class) = Class(
+    dri = dri,
+    name = name,
+    kind = kind,
+    constructors = merge(constructors + other.constructors, Function::mergeWith),
+    functions = merge(functions + other.functions, Function::mergeWith),
+    properties = merge(properties + other.properties, Property::mergeWith),
+    classlikes = merge(classlikes + other.classlikes, Classlike::mergeWith),
+    expected = expected?.mergeWith(other.expected),
+    actual = (actual + other.actual).mergeClassPlatformInfo(),
+    visibility = (visibility + other.visibility)
+)
+
+fun Enum.mergeWith(other: Enum) = Enum(
+    dri = dri,
+    name = name,
+    functions = merge(functions + other.functions, Function::mergeWith),
+    properties = merge(properties + other.properties, Property::mergeWith),
+    classlikes = merge(classlikes + other.classlikes, Classlike::mergeWith),
+    expected = expected?.mergeWith(other.expected),
+    actual = (actual + other.actual).mergeClassPlatformInfo(),
+    entries = (this.entries + other.entries.distinctBy { it.dri }.toList()),
+    constructors = merge(constructors + other.constructors, Function::mergeWith),
+    visibility = visibility
+)
+
+fun Parameter.mergeWith(other: Parameter) = Parameter(
+    dri,
+    name,
+    type,
+    expected?.mergeWith(other.expected),
+    (actual + other.actual).merge()
+)
+
+fun Package.mergeWith(other: Package): Package = Package(
+    dri,
+    merge(functions + other.functions, Function::mergeWith),
+    merge(properties + other.properties, Property::mergeWith),
+    merge(classlikes + other.classlikes, Classlike::mergeWith)
+)
+\ No newline at end of file