Add validator for xmlFlattened + xmlName

smithy-aws-protocol-tests/model/awsQuery/main.smithy

@@ -1,5 +1,15 @@
 $version: "2.0"
 
+metadata suppressions = [
+    {
+        id: "XmlFlattenedTrait"
+        namespace: "aws.protocoltests.query"
+        reason: """
+            Some tests are for asserting the correct behavior in the case that
+            xmlFlattened is wrong and trips this validator."""
+    }
+]
+
 namespace aws.protocoltests.query
 
 use aws.api#service

smithy-aws-protocol-tests/model/ec2Query/main.smithy

@@ -26,6 +26,16 @@
 
 $version: "2.0"
 
+metadata suppressions = [
+    {
+        id: "XmlFlattenedTrait"
+        namespace: "aws.protocoltests.ec2"
+        reason: """
+            Some tests are for asserting the correct behavior in the case that
+            xmlFlattened is wrong and trips this validator."""
+    }
+]
+
 namespace aws.protocoltests.ec2
 
 use aws.api#service

smithy-aws-protocol-tests/model/restXml/main.smithy

@@ -1,5 +1,15 @@
 $version: "2.0"
 
+metadata suppressions = [
+    {
+        id: "XmlFlattenedTrait"
+        namespace: "aws.protocoltests.restxml"
+        reason: """
+            Some tests are for asserting the correct behavior in the case that
+            xmlFlattened is wrong and trips this validator."""
+    }
+]
+
 namespace aws.protocoltests.restxml
 
 use aws.api#service

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

@@ -0,0 +1,51 @@
+/*
+ * 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 java.util.Optional;
+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;
+            }
+
+            model.getShape(member.getTarget())
+                    .flatMap(Shape::asListShape)
+                    .flatMap(listShape -> validateMemberTargetingList(member, listShape))
+                    .ifPresent(events::add);
+        }
+        return events;
+    }
+
+    private Optional<ValidationEvent> validateMemberTargetingList(MemberShape member, ListShape targetList) {
+        return targetList.getMember().getTrait(XmlNameTrait.class)
+                .filter(xmlName -> !member.getMemberName().equals(xmlName.getValue()))
+                .map(xmlName -> 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
+}