Memoize default values in Schema, not Field

Author: kubukoz

modules/core/src/smithy4s/schema/Field.scala

@@ -41,7 +41,7 @@ final case class Field[S, A](
   @deprecated("use .schema instead", since = "0.18.0")
   final def instance: Schema[A] = schema
 
-  lazy val getDefaultValue: Option[A] =
+  def getDefaultValue: Option[A] =
     schema.getDefaultValue
 
   def isDefaultValue(a: A): Boolean = getDefaultValue.contains(a)

modules/core/src/smithy4s/schema/Schema.scala

@@ -104,14 +104,15 @@ sealed trait Schema[A]{
   final def getDefault: Option[Document] =
     this.hints.get(smithy.api.Default).map(_.value)
 
-  final def getDefaultValue: Option[A] = {
+  private final lazy val defaultValue: Option[A] = {
     val maybeDefault = getDefault.flatMap[A] {
       case Document.DNull => this.compile(DefaultValueSchemaVisitor)
       case document => Document.Decoder.fromSchema(this).decode(document).toOption
     }
     maybeDefault.orElse(this.compile(OptionDefaultVisitor))
   }
 
+  final def getDefaultValue: Option[A] = defaultValue
 
   /**
     * When applied on a structure schema, creates a schema that, when compiled into