Suppress useless companion for Kotlin-As-Java (#2681)

1 files changed, 70 insertions, 0 deletions

diff --git a/plugins/kotlin-as-java/src/main/kotlin/converters/KotlinCompanion.kt b/plugins/kotlin-as-java/src/main/kotlin/converters/KotlinCompanion.kt
new file mode 100644
index 00000000..dec1591a
--- /dev/null
+++ b/plugins/kotlin-as-java/src/main/kotlin/converters/KotlinCompanion.kt
@@ -0,0 +1,70 @@
+package org.jetbrains.dokka.kotlinAsJava.converters
+
+import org.jetbrains.dokka.links.Callable
+import org.jetbrains.dokka.model.*
+import org.jetbrains.dokka.model.properties.PropertyContainer
+
+private const val DEFAULT_COMPANION_NAME = "Companion"
+
+internal fun DObject?.staticFunctionsForJava(): List<DFunction> {
+    if (this == null) return emptyList()
+    return functions.filter { it.isJvmStatic }
+}
+
+/**
+ * @return properties that will be visible as static for java.
+ * See [Static fields](https://kotlinlang.org/docs/java-to-kotlin-interop.html#static-fields)
+ */
+internal fun DObject?.staticPropertiesForJava(): List<DProperty> {
+    if (this == null) return emptyList()
+    return properties.filter { it.isJvmField || it.isConst || it.isLateInit }
+}
+
+internal fun DObject.companionInstancePropertyForJava(): DProperty? {
+    if (hasNothingToRender()) return null // do not show if companion not rendered
+
+    return DProperty(
+        name = name ?: DEFAULT_COMPANION_NAME,
+        modifier = sourceSets.associateWith { JavaModifier.Final },
+        dri = dri.copy(callable = Callable(name ?: DEFAULT_COMPANION_NAME, null, emptyList())),
+        documentation = emptyMap(),
+        sources = emptyMap(),
+        visibility = sourceSets.associateWith {
+            JavaVisibility.Public
+        },
+        type = GenericTypeConstructor(dri, emptyList()),
+        setter = null,
+        getter = null,
+        sourceSets = sourceSets,
+        receiver = null,
+        generics = emptyList(),
+        expectPresentInSet = expectPresentInSet,
+        isExpectActual = false,
+        extra = PropertyContainer.withAll(sourceSets.map {
+            mapOf(it to setOf(ExtraModifiers.JavaOnlyModifiers.Static)).toAdditionalModifiers()
+        })
+    )
+}
+
+internal fun DObject.companionAsJava(): DObject? {
+    if (hasNothingToRender()) return null
+
+    return asJava(
+        excludedProps = staticPropertiesForJava(),
+        excludedFunctions = staticFunctionsForJava()
+    )
+}
+
+/**
+ * Hide companion object if there isn't members of parents.
+ * Properties and functions that are moved to outer class are not counted as members.
+ */
+private fun DObject.hasNothingToRender(): Boolean {
+    val nonStaticPropsCount = properties.size - staticPropertiesForJava().size
+    val nonStaticFunctionsCount = functions.size - staticFunctionsForJava().size
+    val classLikesCount = classlikes.size
+    val superTypesCount = supertypes.values.firstOrNull()?.size ?: 0
+
+    return nonStaticFunctionsCount + nonStaticPropsCount +
+            classLikesCount + superTypesCount == 0
+}