Fix Null Reference for ScaledObject without Extensions (#2793)

* Fix possible null reference

* Refactor tests

Author: wsugarman

src/Azure.Functions.Cli/Kubernetes/KEDA/V2/KedaV2Resource.cs

@@ -56,7 +56,7 @@ private static bool IsDurable(JToken trigger) =>
         private static IEnumerable<ScaledObjectTriggerV1Alpha1> GetDurableScalar(JObject hostJson)
         {
             // Reference: https://docs.microsoft.com/azure/azure-functions/durable/durable-functions-bindings#durable-functions-2-0-host-json
-            DurableTaskConfig durableTaskConfig = hostJson.SelectToken("extensions.durableTask").ToObject<DurableTaskConfig>();
+            DurableTaskConfig durableTaskConfig = hostJson.SelectToken("extensions.durableTask")?.ToObject<DurableTaskConfig>();
             string storageType = durableTaskConfig?.StorageProvider?["type"]?.ToString();
 
             // Custom storage types are supported starting in Durable Functions v2.4.2

test/Azure.Functions.Cli.Tests/KedaV2ResourceTests.cs

@@ -35,6 +35,20 @@ public KedaV2ResourceTests()
 "));
         }
 
+        [Theory]
+        [InlineData("{ }")]
+        [InlineData("{ \"extensions\": null }")]
+        [InlineData("{ \"extensions\": { } }")]
+        [InlineData("{ \"extensions\": { \"durableTask\": null } }")]
+        public void GetDurableScalarNoExtension(string hostSnippet)
+        {
+            JObject hostConfig = JObject.Parse(hostSnippet);
+            ScaledObjectKedaV2 scaledObject = GetKubernetesResource(hostConfig);
+
+            Assert.NotNull(scaledObject);
+            Assert.Empty(scaledObject.Spec.Triggers);
+        }
+
         [Theory]
         [InlineData(null)]
         [InlineData("{ }")]
@@ -58,16 +72,7 @@ public void GetUnsupportedDurableScalar(string providerJson)
             if (providerJson != null)
                 durableTaskConfig.Add("storageProvider", JObject.Parse(providerJson));
 
-            KedaV2Resource resource = new KedaV2Resource();
-            ScaledObjectKedaV2 scaledObject = resource.GetKubernetesResource(
-                "HelloWorld",
-                "default",
-                new TriggersPayload { HostJson = hostConfig, FunctionsJson = _functions },
-                new DeploymentV1Apps { Metadata = new ObjectMetadataV1 { Name = "HelloDeployment" } },
-                30,
-                300,
-                1,
-                8) as ScaledObjectKedaV2;
+            ScaledObjectKedaV2 scaledObject = GetKubernetesResource(hostConfig);
 
             Assert.NotNull(scaledObject);
             Assert.Empty(scaledObject.Spec.Triggers);
@@ -106,19 +111,24 @@ public void GetMsSqlDurableScalar(
             if (configuredMaxActivities.HasValue)
                 durableTaskConfig.Add("maxConcurrentActivityFunctions", configuredMaxActivities);
 
+            ScaledObjectKedaV2 scaledObject = GetKubernetesResource(hostConfig);
+
+            Assert.NotNull(scaledObject);
+            AssertMsSqlDurableScalar(scaledObject.Spec.Triggers.Single(), expectedMaxOrchestrations, expectedMaxActivities, "MySqlConnection");
+        }
+
+        private ScaledObjectKedaV2 GetKubernetesResource(JObject hostJson)
+        {
             KedaV2Resource resource = new KedaV2Resource();
-            ScaledObjectKedaV2 scaledObject = resource.GetKubernetesResource(
+            return resource.GetKubernetesResource(
                 "HelloWorld",
                 "default",
-                new TriggersPayload { HostJson = hostConfig, FunctionsJson = _functions },
+                new TriggersPayload { HostJson = hostJson, FunctionsJson = _functions },
                 new DeploymentV1Apps { Metadata = new ObjectMetadataV1 { Name = "HelloDeployment" } },
                 30,
                 300,
                 1,
                 8) as ScaledObjectKedaV2;
-
-            Assert.NotNull(scaledObject);
-            AssertMsSqlDurableScalar(scaledObject.Spec.Triggers.Single(), expectedMaxOrchestrations, expectedMaxActivities, "MySqlConnection");
         }
 
         private static void AssertMsSqlDurableScalar(ScaledObjectTriggerV1Alpha1 actual, int maxOrchestrations, int maxActivities, string connectionString)