Fix missing-x-ms-identifier rule not checking base class for properti…

…es (Azure#1537)

fix [Azure#1358](Azure#1358)

.chronus/changes/fix-x-ms-identifier-inheritance-2024-8-13-21-41-26.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-azure-resource-manager"
+---
+
+Fix missing-x-ms-identifier rule not checking base class for properties

packages/typespec-azure-resource-manager/src/rules/missing-x-ms-identifiers.ts

@@ -60,7 +60,7 @@ export const missingXmsIdentifiersRule = createRule({
       if (Array.isArray(xmsIdentifiers)) {
         for (const prop of xmsIdentifiers) {
           if (typeof prop === "string") {
-            if (!elementType.properties.has(prop)) {
+            if (getProperty(elementType, prop) === undefined) {
               context.reportDiagnostic({
                 messageId: "missingProperty",
                 format: { propertyName: prop, targetModelName: elementType.name },

packages/typespec-azure-resource-manager/test/rules/missing-x-ms-identifiers.test.ts

@@ -95,6 +95,26 @@ describe("typespec-azure-core: no-enum rule", () => {
       )
       .toBeValid();
   });
+
+  it(`doesn't emit diagnostic if x-ms-identifiers property is defined in a base class`, async () => {
+    await tester
+      .expect(
+        `
+        model Foo {
+          @OpenAPI.extension("x-ms-identifiers", ["name"])
+          bar: Child[];
+        }
+
+        model Child extends Base {
+          other: string;
+        }
+
+        model Base { name: string;}
+        `,
+      )
+      .toBeValid();
+  });
+
   it(`doesn't emit diagnostic if element is a primitive type`, async () => {
     await tester
       .expect(