Add support for generic map value types

Author: jhaber

src/main/kotlin/com/coxautodev/graphql/tools/GenericType.kt

@@ -1,5 +1,6 @@
 package com.coxautodev.graphql.tools
 
+import com.fasterxml.classmate.ResolvedType
 import com.google.common.primitives.Primitives
 import org.apache.commons.lang3.reflect.TypeUtils
 import sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl
@@ -131,6 +132,14 @@ internal open class GenericType(protected val mostSpecificType: JavaType, protec
                     val actualTypeArguments = type.actualTypeArguments.map { replaceTypeVariable(it) }.toTypedArray()
                     ParameterizedTypeImpl.make(type.rawType as Class<*>?, actualTypeArguments, type.ownerType)
                 }
+                is ResolvedType -> {
+                    if (type.typeParameters.isEmpty()) {
+                        type.erasedType
+                    } else {
+                        val actualTypeArguments = type.typeParameters.map { replaceTypeVariable(it) }.toTypedArray()
+                        ParameterizedTypeImpl.make(type.erasedType, actualTypeArguments, null)
+                    }
+                }
                 is TypeVariable<*> -> {
                     if (declaringType is ParameterizedType) {
                         TypeUtils.getRawType(type, declaringType)

src/main/kotlin/com/coxautodev/graphql/tools/PropertyMapResolver.kt

@@ -14,25 +14,10 @@ internal class PropertyMapResolver(field: FieldDefinition, search: FieldResolver
 
     var mapGenericValue : JavaType = getMapGenericType(relativeTo)
 
-    /**
-     * this impl still has some problems:
-     * - mapClass lost its generics somewhere along the way, so if you had
-     *   something like {@code class Resolver<V> implements Map<String, V>}
-     *   then we won't be able to infer the value type
-     * - this doesn't handle the case of the map value type being generic,
-     *   for example {@code class Resolver implements Map<String, MyType<MyTypeArg>>}
-     */
     fun getMapGenericType(mapClass : JavaType) : JavaType {
         val resolvedType = TypeResolver().resolve(mapClass)
 
-        val mapValueType = resolvedType.typeParametersFor(Map::class.java)[1]
-        if (mapValueType.typeParameters.isEmpty()) {
-            // no type params should mean regular class
-            return mapValueType.erasedType
-        } else {
-            // TODO raise an error? try to handle this case?
-            return Object::class.java
-        }
+        return resolvedType.typeParametersFor(Map::class.java)[1]
     }
 
     override fun createDataFetcher(): DataFetcher<*> {