Handle union of string values

Author: epabst

src/converter/typeUtils.kt

@@ -115,12 +115,19 @@ private fun ObjectTypeToKotlinTypeMapper.mapUnionType(type: UnionOrIntersectionT
 
     val mappedTypes = notNullTypes.map { mapType(it, null) }
     return KtTypeUnion(when {
-        !nullable -> mappedTypes.distinct()
+        !nullable -> mappedTypes.merge()
         notNullTypes.size == 1 -> mappedTypes.map { it.copy(isNullable = true) }
         else -> (mappedTypes + KtType(NOTHING, isNullable = true)).distinct()
     })
 }
 
+private fun List<KtType>.merge(): List<KtType> {
+    return groupBy { it.copy(comment = null) }.map { entry ->
+        val comments = entry.value.map { it.comment }.filterNotNull()
+        entry.key.copy(comment = if (comments.isEmpty()) null else comments.joinToString(" | "))
+    }
+}
+
 private inline val UnionOrIntersectionType.containsUndefined: Boolean
     get() {
         val array = types.asDynamic()

testData/unionType/stringValues.d.kt

@@ -0,0 +1,5 @@
+package stringValues
+
+external interface MapGenerator {
+    fun generate(scope: String /* "city" | "state" | "country" | "world" */)
+}

testData/unionType/stringValues.d.ts

@@ -0,0 +1,5 @@
+export type GeographicScope = 'city' | 'state' | 'country' | 'world';
+
+export interface MapGenerator {
+    generate(scope: GeographicScope)
+}