breakfix: convert public access block config fields to nilable like s3

.changelog/08c84fb2c6644d8b983c9986c770cfda.json

@@ -0,0 +1,8 @@
+{
+    "id": "08c84fb2-c664-4d8b-983c-9986c770cfda",
+    "type": "feature",
+    "description": "**BREAK FIX**: Convert S3Control PublicAccessBlock field types to nilable. See #2384, #2162.",
+    "modules": [
+        "service/s3control"
+    ]
+}

codegen/smithy-aws-go-codegen/src/main/java/software/amazon/smithy/aws/go/codegen/customization/RemoveDefaults.java

@@ -0,0 +1,53 @@
+package software.amazon.smithy.aws.go.codegen.customization;
+
+import software.amazon.smithy.go.codegen.GoSettings;
+import software.amazon.smithy.go.codegen.integration.GoIntegration;
+import software.amazon.smithy.model.Model;
+import software.amazon.smithy.model.shapes.Shape;
+import software.amazon.smithy.model.shapes.AbstractShapeBuilder;
+import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.traits.DefaultTrait;
+import software.amazon.smithy.model.transform.ModelTransformer;
+import software.amazon.smithy.utils.MapUtils;
+import software.amazon.smithy.utils.SetUtils;
+import software.amazon.smithy.utils.ToSmithyBuilder;
+
+import java.util.Map;
+import java.util.Set;
+
+public class RemoveDefaults implements GoIntegration {
+    private static final Map<ShapeId, Set<ShapeId>> toRemove = MapUtils.of(
+            ShapeId.from("com.amazonaws.s3control#AWSS3ControlServiceV20180820"), SetUtils.of(
+                    ShapeId.from("com.amazonaws.s3control#PublicAccessBlockConfiguration$BlockPublicAcls"),
+                    ShapeId.from("com.amazonaws.s3control#PublicAccessBlockConfiguration$IgnorePublicAcls"),
+                    ShapeId.from("com.amazonaws.s3control#PublicAccessBlockConfiguration$BlockPublicPolicy"),
+                    ShapeId.from("com.amazonaws.s3control#PublicAccessBlockConfiguration$RestrictPublicBuckets")
+            )
+    );
+
+    private boolean mustPreprocess(ShapeId service) {
+        return toRemove.containsKey(service);
+    }
+
+    @Override
+    public Model preprocessModel(Model model, GoSettings settings) {
+        var serviceId = settings.getService();
+        return mustPreprocess(serviceId)
+                ? removeDefaults(model, toRemove.get(serviceId))
+                : model;
+    }
+
+    private Model removeDefaults(Model model, Set<ShapeId> fromShapes) {
+        return ModelTransformer.create().mapShapes(model, it ->
+                fromShapes.contains(it.getId())
+                        ? withoutDefault(it)
+                        : it
+        );
+    }
+
+    private Shape withoutDefault(Shape shape) {
+        return Shape.shapeToBuilder(shape)
+                .removeTrait(DefaultTrait.ID)
+                .build();
+    }
+}

codegen/smithy-aws-go-codegen/src/main/resources/META-INF/services/software.amazon.smithy.go.codegen.integration.GoIntegration

@@ -68,3 +68,4 @@ software.amazon.smithy.aws.go.codegen.customization.auth.EndpointAuthResolution
 software.amazon.smithy.aws.go.codegen.customization.auth.AwsSigV4aAuthScheme
 software.amazon.smithy.aws.go.codegen.customization.auth.LegacyAuthContextOverride
 software.amazon.smithy.aws.go.codegen.customization.auth.IgnoreAnonymousCredentials
+software.amazon.smithy.aws.go.codegen.customization.RemoveDefaults