add tests for empty first page

test/azure/AcceptanceTests/asynctests/test_paging.py

@@ -224,6 +224,14 @@ async def test_get_multiple_pages_lro(self, client):
         assert items[0].properties.id == 1
         assert items[1].properties.id == 2
 
+    @pytest.mark.asyncio
+    async def test_initial_response_no_items(self, client):
+        pages = client.paging.first_response_empty()
+        items = []
+        async for item in pages:
+            items.append(item)
+        assert len(items) == 1
+
     @pytest.mark.asyncio
     async def test_item_name_with_xms_client_name(self, client):
         pages = client.paging.get_paging_model_with_item_name_with_xms_client_name()

test/azure/AcceptanceTests/test_paging.py

@@ -174,6 +174,11 @@ def test_item_name_with_xms_client_name(self, client):
         items = [i for i in pages]
         assert len(items) == 1
 
+    def test_initial_response_no_items(self, client):
+        pages = client.paging.first_response_empty()
+        items = [i for i in pages]
+        assert len(items) == 1
+
     def test_models(self):
         from paging.models import OperationResult
         if sys.version_info >= (3,5):

test/azure/Expected/AcceptanceTests/Paging/paging/aio/operations/_paging_operations.py

@@ -228,6 +228,68 @@ async def get_next(next_link=None):
         )
     get_single_pages.metadata = {'url': '/paging/single'}  # type: ignore
 
+    @distributed_trace
+    def first_response_empty(
+        self,
+        **kwargs
+    ) -> AsyncIterable["models.ProductResultValue"]:
+        """A paging operation whose first response's items list is empty, but still returns a next link.
+        Second (and final) call, will give you an items list of 1.
+
+        :keyword callable cls: A custom type or function that will be passed the direct response
+        :return: An iterator like instance of either ProductResultValue or the result of cls(response)
+        :rtype: ~azure.core.async_paging.AsyncItemPaged[~paging.models.ProductResultValue]
+        :raises: ~azure.core.exceptions.HttpResponseError
+        """
+        cls = kwargs.pop('cls', None)  # type: ClsType["models.ProductResultValue"]
+        error_map = {
+            401: ClientAuthenticationError, 404: ResourceNotFoundError, 409: ResourceExistsError
+        }
+        error_map.update(kwargs.pop('error_map', {}))
+        accept = "application/json"
+
+        def prepare_request(next_link=None):
+            # Construct headers
+            header_parameters = {}  # type: Dict[str, Any]
+            header_parameters['Accept'] = self._serialize.header("accept", accept, 'str')
+
+            if not next_link:
+                # Construct URL
+                url = self.first_response_empty.metadata['url']  # type: ignore
+                # Construct parameters
+                query_parameters = {}  # type: Dict[str, Any]
+
+                request = self._client.get(url, query_parameters, header_parameters)
+            else:
+                url = next_link
+                query_parameters = {}  # type: Dict[str, Any]
+                request = self._client.get(url, query_parameters, header_parameters)
+            return request
+
+        async def extract_data(pipeline_response):
+            deserialized = self._deserialize('ProductResultValue', pipeline_response)
+            list_of_elem = deserialized.value
+            if cls:
+                list_of_elem = cls(list_of_elem)
+            return deserialized.next_link or None, AsyncList(list_of_elem)
+
+        async def get_next(next_link=None):
+            request = prepare_request(next_link)
+
+            pipeline_response = await self._client._pipeline.run(request, stream=False, **kwargs)
+            response = pipeline_response.http_response
+
+            if response.status_code not in [200]:
+                map_error(status_code=response.status_code, response=response, error_map=error_map)
+                raise HttpResponseError(response=response, error_format=ARMErrorFormat)
+
+            return pipeline_response
+
+        return AsyncItemPaged(
+            get_next, extract_data
+        )
+    first_response_empty.metadata = {'url': '/paging/firstResponseEmpty/1'}  # type: ignore
+
     @distributed_trace
     def get_multiple_pages(
         self,

test/azure/Expected/AcceptanceTests/Paging/paging/operations/_paging_operations.py

@@ -234,6 +234,69 @@ def get_next(next_link=None):
         )
     get_single_pages.metadata = {'url': '/paging/single'}  # type: ignore
 
+    @distributed_trace
+    def first_response_empty(
+        self,
+        **kwargs  # type: Any
+    ):
+        # type: (...) -> Iterable["models.ProductResultValue"]
+        """A paging operation whose first response's items list is empty, but still returns a next link.
+        Second (and final) call, will give you an items list of 1.
+
+        :keyword callable cls: A custom type or function that will be passed the direct response
+        :return: An iterator like instance of either ProductResultValue or the result of cls(response)
+        :rtype: ~azure.core.paging.ItemPaged[~paging.models.ProductResultValue]
+        :raises: ~azure.core.exceptions.HttpResponseError
+        """
+        cls = kwargs.pop('cls', None)  # type: ClsType["models.ProductResultValue"]
+        error_map = {
+            401: ClientAuthenticationError, 404: ResourceNotFoundError, 409: ResourceExistsError
+        }
+        error_map.update(kwargs.pop('error_map', {}))
+        accept = "application/json"
+
+        def prepare_request(next_link=None):
+            # Construct headers
+            header_parameters = {}  # type: Dict[str, Any]
+            header_parameters['Accept'] = self._serialize.header("accept", accept, 'str')
+
+            if not next_link:
+                # Construct URL
+                url = self.first_response_empty.metadata['url']  # type: ignore
+                # Construct parameters
+                query_parameters = {}  # type: Dict[str, Any]
+
+                request = self._client.get(url, query_parameters, header_parameters)
+            else:
+                url = next_link
+                query_parameters = {}  # type: Dict[str, Any]
+                request = self._client.get(url, query_parameters, header_parameters)
+            return request
+
+        def extract_data(pipeline_response):
+            deserialized = self._deserialize('ProductResultValue', pipeline_response)
+            list_of_elem = deserialized.value
+            if cls:
+                list_of_elem = cls(list_of_elem)
+            return deserialized.next_link or None, iter(list_of_elem)
+
+        def get_next(next_link=None):
+            request = prepare_request(next_link)
+
+            pipeline_response = self._client._pipeline.run(request, stream=False, **kwargs)
+            response = pipeline_response.http_response
+
+            if response.status_code not in [200]:
+                map_error(status_code=response.status_code, response=response, error_map=error_map)
+                raise HttpResponseError(response=response, error_format=ARMErrorFormat)
+
+            return pipeline_response
+
+        return ItemPaged(
+            get_next, extract_data
+        )
+    first_response_empty.metadata = {'url': '/paging/firstResponseEmpty/1'}  # type: ignore
+
     @distributed_trace
     def get_multiple_pages(
         self,