Copy attributes back post de-serializing array

lib/serializer.ts

@@ -735,7 +735,15 @@ function deserializeCompositeType(
       // paging
       if (Array.isArray(responseBody[key]) && modelProps[key].serializedName === "") {
         propertyInstance = responseBody[key];
-        instance = serializer.deserialize(propertyMapper, propertyInstance, propertyObjectName);
+        const arrayInstance = serializer.deserialize(propertyMapper, propertyInstance, propertyObjectName);
+        // Copy over any properties that have already been added into the instance, where they do
+        // not exist on the newly de-serialized array
+        Object.entries(instance).forEach(([key, value]) => {
+          if (!arrayInstance.hasOwnProperty(key)) {
+            arrayInstance[key] = value;
+          }
+        });
+        instance = arrayInstance
       } else if (propertyInstance !== undefined || propertyMapper.defaultValue !== undefined) {
         serializedValue = serializer.deserialize(
           propertyMapper,

test/data/TestClient/lib/models/mappers.ts

@@ -473,6 +473,36 @@ internalMappers.ProductListResultNextLink = {
     },
   },
 };
+internalMappers.ProductListResultNextLinkFirst = {
+  required: false,
+  serializedName: "ProductListResultNextLinkFirst",
+  type: {
+    name: "Composite",
+    className: "ProductListResultNextLinkFirst",
+    modelProperties: {
+      nextLink: {
+        serializedName: "nextLink",
+        required: false,
+        type: {
+          name: "String",
+        },
+      },
+      value: {
+        serializedName: "",
+        required: false,
+        type: {
+          name: "Sequence",
+          element: {
+            type: {
+              name: "Composite",
+              className: "Product",
+            },
+          },
+        },
+      },
+    },
+  },
+};
 internalMappers.SawShark = {
   required: false,
   serializedName: "sawshark",

test/serializationTests.ts

@@ -1100,6 +1100,50 @@ describe("msrest", function () {
       done();
     });
 
+    it("should correctly deserialize a pageable type with nextLink first in mapper", function (done) {
+      const client = new TestClient("http://localhost:9090");
+      const mapper = Mappers.ProductListResultNextLinkFirst;
+      const responseBody = {
+        value: [
+          {
+            id: 101,
+            name: "TestProduct",
+            properties: {
+              provisioningState: "Succeeded",
+            },
+          },
+          {
+            id: 104,
+            name: "TestProduct1",
+            properties: {
+              provisioningState: "Failed",
+            },
+          },
+        ],
+        nextLink: "https://helloworld.com",
+      };
+      const deserializedProduct = client.serializer.deserialize(
+        mapper,
+        responseBody,
+        "responseBody"
+      );
+      Array.isArray(deserializedProduct).should.be.true;
+      deserializedProduct.length.should.equal(2);
+      deserializedProduct.nextLink.should.equal("https://helloworld.com");
+      for (let i = 0; i < deserializedProduct.length; i++) {
+        if (i === 0) {
+          deserializedProduct[i].id.should.equal(101);
+          deserializedProduct[i].name.should.equal("TestProduct");
+          deserializedProduct[i].provisioningState.should.equal("Succeeded");
+        } else if (i === 1) {
+          deserializedProduct[i].id.should.equal(104);
+          deserializedProduct[i].name.should.equal("TestProduct1");
+          deserializedProduct[i].provisioningState.should.equal("Failed");
+        }
+      }
+      done();
+    });
+
     it("should correctly deserialize object version of polymorphic discriminator", function (done) {
       const client = new TestClient("http://localhost:9090");
       const mapper = Mappers.Fish;