Add xmlName trait docs

Author: JordonPhillips

smithy-docgen-core/src/main/java/software/amazon/smithy/docgen/core/integrations/BuiltinsIntegration.java

@@ -33,6 +33,7 @@
 import software.amazon.smithy.docgen.core.interceptors.SparseInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.UniqueItemsInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.UnstableInterceptor;
+import software.amazon.smithy.docgen.core.interceptors.XmlNameInterceptor;
 import software.amazon.smithy.docgen.core.writers.DocWriter;
 import software.amazon.smithy.docgen.core.writers.MarkdownWriter;
 import software.amazon.smithy.utils.CodeInterceptor;
@@ -77,6 +78,7 @@ public List<? extends CodeInterceptor<? extends CodeSection, DocWriter>> interce
                 new OperationAuthInterceptor(),
                 new ApiKeyAuthInterceptor(),
                 new JsonNameInterceptor(),
+                new XmlNameInterceptor(),
                 new PaginationInterceptor(),
                 new RequestCompressionInterceptor(),
                 new NoReplaceBindingInterceptor(),

smithy-docgen-core/src/main/java/software/amazon/smithy/docgen/core/interceptors/XmlNameInterceptor.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.docgen.core.interceptors;
+
+import software.amazon.smithy.docgen.core.sections.ProtocolSection;
+import software.amazon.smithy.docgen.core.writers.DocWriter;
+import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.traits.XmlNameTrait;
+import software.amazon.smithy.utils.SmithyInternalApi;
+
+/**
+ * Adds a member's <a href="https://smithy.io/2.0/spec/protocol-traits.html#xmlname-trait">
+ * xmlName</a> to the {@link ProtocolSection} if the protocol supports it.
+ */
+@SmithyInternalApi
+public final class XmlNameInterceptor extends ProtocolTraitInterceptor<XmlNameTrait> {
+    @Override
+    protected Class<XmlNameTrait> getTraitClass() {
+        return XmlNameTrait.class;
+    }
+
+    @Override
+    protected ShapeId getTraitId() {
+        return XmlNameTrait.ID;
+    }
+
+    @Override
+    public boolean isIntercepted(ProtocolSection section) {
+        // The xmlName trait uniquely doesn't inherit values from the target as a member.
+        return super.isIntercepted(section) && section.shape().hasTrait(XmlNameTrait.class);
+    }
+
+    @Override
+    void write(DocWriter writer, String previousText, ProtocolSection section, XmlNameTrait trait) {
+        writer.putContext("xmlTagName", "XML tag name:");
+        writer.write("""
+                ${xmlTagName:B} $`
+
+                $L""", trait.getValue(), previousText);
+    }
+}