Warn when update operations use default values

smithy-model/src/main/java/software/amazon/smithy/model/validation/validators/DefaultValueInUpdateValidator.java

@@ -0,0 +1,76 @@
+package software.amazon.smithy.model.validation.validators;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Locale;
+import java.util.Set;
+import java.util.TreeSet;
+import software.amazon.smithy.model.Model;
+import software.amazon.smithy.model.shapes.MemberShape;
+import software.amazon.smithy.model.shapes.OperationShape;
+import software.amazon.smithy.model.shapes.ResourceShape;
+import software.amazon.smithy.model.shapes.StructureShape;
+import software.amazon.smithy.model.traits.DefaultTrait;
+import software.amazon.smithy.model.validation.AbstractValidator;
+import software.amazon.smithy.model.validation.ValidationEvent;
+import software.amazon.smithy.utils.SetUtils;
+
+/**
+ * Finds operations that are meant to partially update a resource, but that use
+ * members with default values in their input shapes, making it impossible
+ * to know if the member was provided explicitly or defaulted.
+ */
+public final class DefaultValueInUpdateValidator extends AbstractValidator {
+
+    // Look for operation names that start with update or patch.
+    private static final Set<String> OPERATION_NAMES_TO_CHECK = SetUtils.of("update", "patch");
+
+    @Override
+    public List<ValidationEvent> validate(Model model) {
+        List<ValidationEvent> events = new ArrayList<>();
+        Set<String> defaultedMembers = new TreeSet<>();
+
+        for (OperationShape operation : identifyOperations(model)) {
+            StructureShape input = model.expectShape(operation.getInputShape(), StructureShape.class);
+
+            for (MemberShape member : input.getAllMembers().values()) {
+                if (member.hasTrait(DefaultTrait.class)) {
+                    defaultedMembers.add(member.getMemberName());
+                }
+            }
+
+            if (!defaultedMembers.isEmpty()) {
+                events.add(warning(operation, "This update style operation has top-level input members marked with "
+                                              + "the @default trait. It will be impossible to tell if the member was "
+                                              + "omitted or explicitly provided. Affected members: "
+                                              + defaultedMembers));
+                defaultedMembers.clear();
+            }
+        }
+
+        return events;
+    }
+
+    private Set<OperationShape> identifyOperations(Model model) {
+        Set<OperationShape> operationsToCheck = new HashSet<>();
+
+        // Look for operations that have an update lifecycle.
+        for (ResourceShape resource : model.getResourceShapes()) {
+            resource.getUpdate().ifPresent(id -> operationsToCheck.add(model.expectShape(id, OperationShape.class)));
+        }
+
+        // Look for operations based on their names.
+        for (OperationShape operation : model.getOperationShapes()) {
+            String name = operation.getId().getName().toLowerCase(Locale.ENGLISH);
+            for (String prefix : OPERATION_NAMES_TO_CHECK) {
+                if (name.startsWith(prefix)) {
+                    operationsToCheck.add(operation);
+                    break;
+                }
+            }
+        }
+
+        return operationsToCheck;
+    }
+}

smithy-model/src/main/resources/META-INF/services/software.amazon.smithy.model.validation.Validator

@@ -1,4 +1,5 @@
 software.amazon.smithy.model.validation.validators.AuthTraitValidator
+software.amazon.smithy.model.validation.validators.DefaultValueInUpdateValidator
 software.amazon.smithy.model.validation.validators.DeprecatedTraitValidator
 software.amazon.smithy.model.validation.validators.EnumTraitValidator
 software.amazon.smithy.model.validation.validators.EventPayloadTraitValidator

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/default-value-in-update/finds-patch-by-name-with-default.errors

@@ -0,0 +1 @@
+[WARNING] smithy.example#PatchFoo: This update style operation has top-level input members marked with the @default trait. It will be impossible to tell if the member was omitted or explicitly provided. Affected members: [description] | DefaultValueInUpdate

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/default-value-in-update/finds-patch-by-name-with-default.smithy

@@ -0,0 +1,14 @@
+$version: "2.0"
+
+namespace smithy.example
+
+operation PatchFoo {
+    input := {
+        @required
+        id: String
+
+        @default
+        description: String
+    }
+    output := {}
+}

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/default-value-in-update/finds-resource-update-with-default.errors

@@ -0,0 +1 @@
+[WARNING] smithy.example#UpdateFoo: This update style operation has top-level input members marked with the @default trait. It will be impossible to tell if the member was omitted or explicitly provided. Affected members: [description] | DefaultValueInUpdate

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/default-value-in-update/finds-resource-update-with-default.smithy

@@ -0,0 +1,21 @@
+$version: "2.0"
+
+namespace smithy.example
+
+resource Foo {
+    identifiers: {
+        id: String
+    }
+    update: UpdateFoo
+}
+
+operation UpdateFoo {
+    input := {
+        @required
+        id: String
+
+        @default
+        description: String
+    }
+    output := {}
+}

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/default-value-in-update/finds-update-by-name-with-default.errors

@@ -0,0 +1 @@
+[WARNING] smithy.example#UpdateFoo: This update style operation has top-level input members marked with the @default trait. It will be impossible to tell if the member was omitted or explicitly provided. Affected members: [description] | DefaultValueInUpdate

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/default-value-in-update/finds-update-by-name-with-default.smithy

@@ -0,0 +1,14 @@
+$version: "2.0"
+
+namespace smithy.example
+
+operation UpdateFoo {
+    input := {
+        @required
+        id: String
+
+        @default
+        description: String
+    }
+    output := {}
+}