Add validator for xmlFlattened + xmlName

smithy-aws-protocol-tests/model/awsQuery/xml-lists.smithy

@@ -185,8 +185,10 @@ structure XmlListsOutput {
     @xmlName("renamed")
     renamedListMembers: RenamedListMembers,
 
+    @suppress(["XmlFlattenedTrait"])
     @xmlFlattened
     // The xmlname on the targeted list is ignored, and the member name is used.
+    // The validation that flags this is suppressed so we can test this behavior.
     flattenedList: RenamedListMembers,
 
     @xmlName("customName")

smithy-aws-protocol-tests/model/ec2Query/xml-lists.smithy

@@ -183,8 +183,10 @@ structure XmlListsOutput {
     @xmlName("renamed")
     renamedListMembers: RenamedListMembers,
 
+    @suppress(["XmlFlattenedTrait"])
     @xmlFlattened
     // The xmlname on the targeted list is ignored, and the member name is used.
+    // The validation that flags this is suppressed so we can test this behavior.
     flattenedList: RenamedListMembers,
 
     @xmlName("customName")

smithy-aws-protocol-tests/model/restXml/document-lists.smithy

@@ -352,8 +352,10 @@ structure XmlListsInputOutput {
     @xmlName("renamed")
     renamedListMembers: RenamedListMembers,
 
+    @suppress(["XmlFlattenedTrait"])
     @xmlFlattened
     // The xmlname on the targeted list is ignored, and the member name is used.
+    // The validation that flags this is suppressed so we can test this behavior.
     flattenedList: RenamedListMembers,
 
     @xmlName("customName")
@@ -376,7 +378,10 @@ structure XmlListsInputOutput {
     @xmlName("myStructureList")
     structureList: StructureList,
 
+    @suppress(["XmlFlattenedTrait"])
     @xmlFlattened
+    // The xmlname on the targeted list is ignored, and the member name is used.
+    // The validation that flags this is suppressed so we can test this behavior.
     flattenedStructureList: StructureList
 }
 

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

@@ -0,0 +1,54 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.model.validation.validators;
+
+import java.util.ArrayList;
+import java.util.List;
+import software.amazon.smithy.model.Model;
+import software.amazon.smithy.model.shapes.ListShape;
+import software.amazon.smithy.model.shapes.MemberShape;
+import software.amazon.smithy.model.shapes.Shape;
+import software.amazon.smithy.model.traits.XmlFlattenedTrait;
+import software.amazon.smithy.model.traits.XmlNameTrait;
+import software.amazon.smithy.model.validation.AbstractValidator;
+import software.amazon.smithy.model.validation.ValidationEvent;
+
+/**
+ * Validates that xmlFlattened members aren't unintentionally ignoring the
+ * xmlName of their targets.
+ */
+public final class XmlFlattenedTraitValidator extends AbstractValidator {
+    @Override
+    public List<ValidationEvent> validate(Model model) {
+        List<ValidationEvent> events = new ArrayList<>();
+        for (MemberShape member : model.getMemberShapesWithTrait(XmlFlattenedTrait.class)) {
+            // Don't emit the event if they're being explicit about the xmlName on this member
+            if (member.hasTrait(XmlNameTrait.class)) {
+                continue;
+            }
+
+            Shape target = model.expectShape(member.getTarget());
+            if (target instanceof ListShape) {
+                ListShape targetList = (ListShape) target;
+                validateMemberTargetingList(member, targetList, events);
+            }
+        }
+        return events;
+    }
+
+    private void validateMemberTargetingList(MemberShape member, ListShape targetList, List<ValidationEvent> events) {
+        if (targetList.getMember().hasTrait(XmlNameTrait.class)) {
+            XmlNameTrait xmlName = targetList.getMember().expectTrait(XmlNameTrait.class);
+            if (!member.getMemberName().equals(xmlName.getValue())) {
+                events.add(warning(member, String.format(
+                        "Member is `@xmlFlattened`, so `@xmlName` of target's member (`%s`) has no effect."
+                        + " The flattened list elements will have the name of this member - `%s`. If this"
+                        + " is unintended, you can add `@xmlName(\"%s\")` to this member.",
+                        targetList.getMember().getId(), member.getMemberName(), xmlName.getValue())));
+            }
+        }
+    }
+}

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

@@ -59,3 +59,4 @@ software.amazon.smithy.model.validation.validators.UnitTypeValidator
 software.amazon.smithy.model.validation.validators.UnstableTraitValidator
 software.amazon.smithy.model.validation.validators.XmlNamespaceTraitValidator
 software.amazon.smithy.model.validation.validators.TraitValidatorsValidator
+software.amazon.smithy.model.validation.validators.XmlFlattenedTraitValidator

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/xml-flattened-and-name.errors

@@ -0,0 +1 @@
+[WARNING] smithy.example#Struct$flattenedNoXmlName: Member is `@xmlFlattened`, so `@xmlName` of target's member (`smithy.example#ListWithXmlName$member`) has no effect. The flattened list elements will have the name of this member - `flattenedNoXmlName`. If this is unintended, you can add `@xmlName("customMember")` to this member. | XmlFlattenedTrait

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/xml-flattened-and-name.smithy

@@ -0,0 +1,43 @@
+$version: "2"
+
+namespace smithy.example
+
+structure Struct {
+    // No event because not flattened
+    notFlattened: ListWithXmlName
+
+    // Event because flattened and non-matching member name
+    @xmlFlattened
+    flattenedNoXmlName: ListWithXmlName
+
+    // No event because the member name matches the xml name
+    @xmlFlattened
+    customMember: ListWithXmlName
+
+    // No event because you're being explicit about the name to use
+    @xmlFlattened
+    @xmlName("customMember")
+    flattenedMatchingXmlName: ListWithXmlName
+
+    // No event because you're being explicit about the name to use
+    @xmlFlattened
+    @xmlName("Bar")
+    flattenedNonMatchingXmlName: ListWithXmlName
+
+    // Validator doesn't apply to maps
+    @xmlFlattened
+    flattenedMap: MapWithXmlName
+}
+
+list ListWithXmlName {
+    @xmlName("customMember")
+    member: String
+}
+
+map MapWithXmlName {
+    @xmlName("customKey")
+    key: String
+
+    @xmlName("customValue")
+    value: String
+}