[notification-hubs] fix TypeError when parsing AppleTemplateRegistrationDescription (#36114)

Currently `getHeadersOrUndefined` incorrectly assumes that the
`ApnsHeaders` parsed from XML is always an array. However, for single
XML element the XML parser gives back an object instead. This change
ensures we are iterating over an array.

One alternative approach is to add an option to `core-xml` specifying
whether to treat certain single xml elements as an object or the single
item of an array. Our underlying XML parser `fast-xml-parser` allows
passing in a `isArray: (name, jpath, isLeafNode, isAttribute) =>
boolean` predicate but it is specific to `fast-xml-parser` and it needs
more discussion on how to properly expose it in `core-xml`. For this
targeted scenario, it is good enough to check whether the parsed result
is an array. This package uses same pattern in other places too, for
example,
https://github.com/Azure/azure-sdk-for-js/blob/953fcf9f84b/sdk/notificationhubs/notification-hubs/src/serializers/notificationHubJobSerializer.ts#L61

Author: jeremymeng

sdk/notificationhubs/notification-hubs/CHANGELOG.md

@@ -1,14 +1,10 @@
 # Release History
 
-## 2.0.2 (Unreleased)
-
-### Features Added
-
-### Breaking Changes
+## 2.0.2 (2025-10-07)
 
 ### Bugs Fixed
 
-### Other Changes
+- Properly handle single-element headers of template registrations [PR #36114](https://github.com/Azure/azure-sdk-for-js/pull/36114).
 
 ## 2.0.0 (2024-10-14)
 

sdk/notificationhubs/notification-hubs/src/serializers/registrationSerializer.ts

@@ -502,14 +502,14 @@ export const registrationDescriptionParser: RegistrationDescriptionParser = {
 };
 
 function getHeadersOrUndefined(
-  value?: { Header: string; Value: string }[],
+  value?: { Header: string; Value: string }[] | { Header: string; Value: string },
 ): Record<string, string> | undefined {
   if (!isDefined(value)) {
     return undefined;
   }
 
   const headerObj: Record<string, string> = {};
-  for (const { Header, Value } of value) {
+  for (const { Header, Value } of Array.isArray(value) ? value : [value]) {
     headerObj[Header] = Value;
   }
 

sdk/notificationhubs/notification-hubs/test/internal/unit/registrationSerializer.spec.ts

@@ -101,6 +101,24 @@ const APPLE_TEMPLATE_REGISTRATION = `<?xml version="1.0" encoding="utf-8"?>
     </content>
 </entry>`;
 
+const APPLE_TEMPLATE_REGISTRATION_SINGLE_APNSHEADER = `<?xml version="1.0" encoding="utf-8"?>
+<entry xmlns="http://www.w3.org/2005/Atom">
+    <content type="application/xml">
+        <AppleTemplateRegistrationDescription xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/netservices/2010/10/servicebus/connect">
+            <Tags>myTag,myOtherTag</Tags>
+            <RegistrationId>{Registration Id}</RegistrationId> 
+            <DeviceToken>{DeviceToken}</DeviceToken> 
+            <BodyTemplate><![CDATA[{Template for the body}]]></BodyTemplate>
+            <ApnsHeaders>
+                <ApnsHeader>
+                    <Header>apns-priority</Header>
+                    <Value>10</Value>
+                </ApnsHeader>
+            </ApnsHeaders>
+        </AppleTemplateRegistrationDescription>
+    </content>
+</entry>`;
+
 const BAIDU_REGISTRATION = `<?xml version="1.0" encoding="utf-8"?>
 <entry xmlns="http://www.w3.org/2005/Atom">
     <content type="application/xml">
@@ -337,6 +355,19 @@ describe("parseRegistrationEntry", () => {
     assert.equal(registration.apnsHeaders!["apns-expiration"], "0");
   });
 
+  it("should parse an apple template registration description with single apns header", async () => {
+    const registration = (await registrationDescriptionParser.parseRegistrationEntry(
+      APPLE_TEMPLATE_REGISTRATION_SINGLE_APNSHEADER,
+    )) as AppleTemplateRegistrationDescription;
+
+    assert.equal(registration.kind, "AppleTemplate");
+    assert.equal(registration.registrationId, "{Registration Id}");
+    assert.equal(registration.deviceToken, "{DeviceToken}");
+    assert.deepEqual(registration.tags, ["myTag", "myOtherTag"]);
+    assert.equal(registration.bodyTemplate, "{Template for the body}");
+    assert.equal(registration.apnsHeaders!["apns-priority"], "10");
+  });
+
   it("should parse an Baidu registration description", async () => {
     const registration = (await registrationDescriptionParser.parseRegistrationEntry(
       BAIDU_REGISTRATION,