Fix Upgrade1to2Command for Set shape

smithy-cli/src/main/java/software/amazon/smithy/cli/commands/Upgrade1to2Command.java

@@ -45,7 +45,9 @@
 import software.amazon.smithy.model.SourceLocation;
 import software.amazon.smithy.model.loader.ModelAssembler;
 import software.amazon.smithy.model.loader.Prelude;
+import software.amazon.smithy.model.shapes.ListShape;
 import software.amazon.smithy.model.shapes.MemberShape;
+import software.amazon.smithy.model.shapes.SetShape;
 import software.amazon.smithy.model.shapes.Shape;
 import software.amazon.smithy.model.shapes.ShapeType;
 import software.amazon.smithy.model.shapes.ShapeVisitor;
@@ -321,6 +323,19 @@ public Void stringShape(StringShape shape) {
             return null;
         }
 
+        @Override
+        public Void listShape(ListShape shape) {
+            getDefault(shape);
+            if (shape instanceof SetShape) {
+                int lineNumber = shape.getSourceLocation().getLine();
+                writer.eraseLine(lineNumber);
+                writer.insertLine(lineNumber, "list " + shape.toShapeId().getName() + " {");
+                writer.insertLine(lineNumber, "@uniqueItems");
+            }
+
+            return null;
+        }
+
         private String serializeEnum(StringShape shape) {
             // Strip all the traits from the shape except the enum trait.
             // We're leaving the other traits where they are in the model

smithy-cli/src/test/resources/software/amazon/smithy/cli/commands/upgrade/cases/box.v2.smithy

@@ -24,7 +24,8 @@ list BadSparseList {
     member: NonBoxedInteger,
 }
 
-set BadSparseSet {
+@uniqueItems
+list BadSparseSet {
     member: NonBoxedInteger,
 }