Fix the ArgumentNull exception (#537)

* Fix the ArgumentNull exception



Co-authored-by: Sander Molenkamp <a.molenkamp@gmail.com>
Co-authored-by: Ryan Nowak <nowakra@gmail.com>

src/Dapr.AspNetCore/StateEntryModelBinder.cs

@@ -69,15 +69,26 @@ namespace Dapr.AspNetCore
                 bindingContext.ModelState.TryAddModelError(bindingContext.ModelName, message);
                 return;
             }
-
+ 
             var obj = await this.thunk(daprClient, this.storeName, key);
-            bindingContext.Result = ModelBindingResult.Success(obj);
 
-            bindingContext.ValidationState.Add(bindingContext.Result.Model, new ValidationStateEntry()
+            // When the state isn't found in the state store:
+            // - If the StateEntryModelBinder is associated with a value of type StateEntry<T>, then the above call returns an object of type
+            //   StateEntry<T> which is non-null, but StateEntry<T>.Value is null
+            // - If the StateEntryModelBinder is associated with a value of type T, then the above call returns a null value.
+            if (obj == null)
             {
-                // Don't do validation since the data came from a trusted source.
-                SuppressValidation = true,
-            });
+                bindingContext.Result = ModelBindingResult.Failed();
+            }
+            else
+            {
+                bindingContext.Result = ModelBindingResult.Success(obj);
+                bindingContext.ValidationState.Add(bindingContext.Result.Model, new ValidationStateEntry()
+                {
+                    // Don't do validation since the data came from a trusted source.
+                    SuppressValidation = true,
+                });
+            }
         }
 
         private static async Task<object> GetStateEntryAsync<T>(DaprClient daprClient, string storeName, string key)

test/Dapr.AspNetCore.IntegrationTest.App/DaprController.cs

@@ -5,6 +5,7 @@
 
 namespace Dapr.AspNetCore.IntegrationTest.App
 {
+    using System;
     using System.Threading.Tasks;
     using Dapr;
     using Dapr.Client;
@@ -53,5 +54,18 @@ namespace Dapr.AspNetCore.IntegrationTest.App
             // To simulate an action where there's no Dapr attribute, yet MVC still checks the list of available model binder providers.
             return user;
         }
+
+        [HttpGet("controllerwithoutstateentry/{widget}")]
+        public ActionResult<Widget> Get([FromState("testStore")] Widget widget)
+        {
+            return widget;
+        }
+
+        [HttpGet("controllerwithstateentry/{widgetStateEntry}")]
+        public ActionResult<Widget> Get([FromState("testStore")] StateEntry<Widget> widgetStateEntry)
+        {
+            return widgetStateEntry.Value;
+        }
+
     }
 }

test/Dapr.AspNetCore.IntegrationTest/ControllerIntegrationTest.cs

@@ -5,10 +5,12 @@
 
 namespace Dapr.AspNetCore.IntegrationTest
 {
+    using System;
     using System.Net.Http;
     using System.Threading.Tasks;
     using Dapr.AspNetCore.IntegrationTest.App;
     using FluentAssertions;
+    using Newtonsoft.Json;
     using Xunit;
 
     public class ControllerIntegrationTest
@@ -32,6 +34,43 @@ namespace Dapr.AspNetCore.IntegrationTest
             }
         }
 
+        [Fact]
+        public async Task ModelBinder_GetFromStateEntryWithKeyPresentInStateStore_ReturnsStateValue()
+        {
+            using (var factory = new AppWebApplicationFactory())
+            {
+                var httpClient = factory.CreateClient();
+                var daprClient = factory.DaprClient;
+
+                var widget = new Widget() { Size = "small", Count = 17, };
+                await daprClient.SaveStateAsync("testStore", "test", widget);
+                var request = new HttpRequestMessage(HttpMethod.Get, "http://localhost/controllerwithoutstateentry/test");
+                var response = await httpClient.SendAsync(request);
+                response.EnsureSuccessStatusCode();
+                var responseContent = await response.Content.ReadAsStringAsync();
+                var responseWidget = JsonConvert.DeserializeObject<Widget>(responseContent);
+                responseWidget.Size.Should().Be(widget.Size);
+                responseWidget.Count.Should().Be(widget.Count);
+            }
+        }
+
+        [Fact]
+        public async Task ModelBinder_GetFromStateEntryWithKeyNotInStateStore_ReturnsNull()
+        {
+            using (var factory = new AppWebApplicationFactory())
+            {
+                var httpClient = factory.CreateClient();
+                var daprClient = factory.DaprClient;
+
+                var request = new HttpRequestMessage(HttpMethod.Get, "http://localhost/controllerwithoutstateentry/test");
+                var response = await httpClient.SendAsync(request);
+                response.EnsureSuccessStatusCode();
+                var responseContent = await response.Content.ReadAsStringAsync();
+                var responseWidget = JsonConvert.DeserializeObject<Widget>(responseContent);
+                Assert.Null(responseWidget);
+            }
+        }
+
         [Fact]
         public async Task ModelBinder_CanBindFromState_WithStateEntry()
         {
@@ -70,6 +109,43 @@ namespace Dapr.AspNetCore.IntegrationTest
             }
         }
 
+        [Fact]
+        public async Task ModelBinder_GetFromStateEntryWithStateEntry_WithKeyPresentInStateStore()
+        {
+            using (var factory = new AppWebApplicationFactory())
+            {
+                var httpClient = factory.CreateClient();
+                var daprClient = factory.DaprClient;
+
+                var widget = new Widget() { Size = "small", Count = 17, };
+                await daprClient.SaveStateAsync("testStore", "test", widget);
+                var request = new HttpRequestMessage(HttpMethod.Get, "http://localhost/controllerwithstateentry/test");
+                var response = await httpClient.SendAsync(request);
+                response.EnsureSuccessStatusCode();
+                var responseContent = await response.Content.ReadAsStringAsync();
+                var responseWidget = JsonConvert.DeserializeObject<Widget>(responseContent);
+                responseWidget.Size.Should().Be(widget.Size);
+                responseWidget.Count.Should().Be(widget.Count);
+            }
+        }
+
+        [Fact]
+        public async Task ModelBinder_GetFromStateEntryWithStateEntry_WithKeyNotInStateStore()
+        {
+            using (var factory = new AppWebApplicationFactory())
+            {
+                var httpClient = factory.CreateClient();
+                var daprClient = factory.DaprClient;
+
+                var request = new HttpRequestMessage(HttpMethod.Get, "http://localhost/controllerwithstateentry/test");
+                var response = await httpClient.SendAsync(request);
+                response.EnsureSuccessStatusCode();
+                var responseContent = await response.Content.ReadAsStringAsync();
+                var responseWidget = JsonConvert.DeserializeObject<Widget>(responseContent);
+                Assert.Null(responseWidget);
+            }
+        }
+
         [Fact]
         public async Task ModelBinder_CanGetOutOfTheWayWhenTheresNoBinding()
         {

test/Dapr.AspNetCore.Test/StateEntryModelBinderTest.cs

@@ -90,6 +90,46 @@ namespace Dapr.AspNetCore.Test
             context.ValidationState[context.Result.Model].SuppressValidation.Should().BeTrue();
         }
 
+        [Fact]
+        public async Task BindAsync_ReturnsNullForNonExistentStateEntry()
+        {
+            var binder = new StateEntryModelBinder("testStore", "id", isStateEntry: false, typeof(Widget));
+
+            // Configure Client
+            var httpClient = new TestHttpClient();
+            var context = CreateContext(CreateServices(httpClient));
+            context.HttpContext.Request.RouteValues["id"] = "test";
+            var task = binder.BindModelAsync(context);
+
+            httpClient.Requests.TryDequeue(out var entry).Should().BeTrue();
+            await SendResponseWithState<string>(null, entry);
+
+            await task;
+            context.ModelState.IsValid.Should().BeTrue();
+            context.Result.IsModelSet.Should().BeFalse();
+            context.Result.Should().Be(ModelBindingResult.Failed());
+        }
+
+        [Fact]
+        public async Task BindAsync_WithStateEntry_ForNonExistentStateEntry()
+        {
+            var binder = new StateEntryModelBinder("testStore", "id", isStateEntry: true, typeof(Widget));
+
+            // Configure Client
+            var httpClient = new TestHttpClient();
+            var context = CreateContext(CreateServices(httpClient));
+            context.HttpContext.Request.RouteValues["id"] = "test";
+            var task = binder.BindModelAsync(context);
+
+            httpClient.Requests.TryDequeue(out var entry).Should().BeTrue();
+            await SendResponseWithState<string>(null, entry);
+
+            await task;
+            context.ModelState.IsValid.Should().BeTrue();
+            context.Result.IsModelSet.Should().BeTrue();
+            ((StateEntry<Widget>)context.Result.Model).Value.Should().BeNull();
+        }
+
         private static ModelBindingContext CreateContext(IServiceProvider services)
         {
             return new DefaultModelBindingContext()