Need to disable lazy loading by default since it regresses the IBinder imperative binding scenario.

Fix for: Azure/azure-webjobs-sdk#1295

Author: MikeStall

src/WebJobs.Script/Config/ScriptHostConfiguration.cs

@@ -105,6 +105,13 @@ public ScriptHostConfiguration()
         /// </summary>
         public bool IsSelfHost { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether we can lazy load the extensions.
+        /// If true, only load extensions that are explicitly referenced from function.json or method signatures.
+        /// Default to false
+        /// </summary>
+        public bool LazyLoadExtensions { get; set; }
+
         /// <summary>
         /// Gets or sets the <see cref="LogCategoryFilter"/> to use when constructing providers for the
         /// registered <see cref="ILoggerFactory"/>.

src/WebJobs.Script/Host/ScriptHost.cs

@@ -470,6 +470,11 @@ protected virtual void Initialize()
                 var functionMetadata = ReadFunctionMetadata(ScriptConfig, TraceWriter, _startupLogger, FunctionErrors, _settingsManager);
                 var usedBindingTypes = DiscoverBindingTypes(functionMetadata);
 
+                if (!ScriptConfig.LazyLoadExtensions)
+                {
+                    usedBindingTypes = _builtinBindingTypes.Keys.Concat(_builtinScriptBindingTypes.Keys).ToArray();
+                }
+
                 var bindingProviders = LoadBindingProviders(ScriptConfig, hostConfigObject, TraceWriter, _startupLogger, usedBindingTypes);
                 ScriptConfig.BindingProviders = bindingProviders;
 
@@ -1483,6 +1488,14 @@ internal static void ApplyConfiguration(JObject config, ScriptHostConfiguration
                 }
             }
 
+            if (config.TryGetValue("lazyLoadExtensions", out value))
+            {
+                if (value.Type == JTokenType.Boolean)
+                {
+                    scriptConfig.LazyLoadExtensions = (bool)value;
+                }
+            }
+
             if (config.TryGetValue("functionTimeout", out value))
             {
                 TimeSpan requestedTimeout = TimeSpan.Parse((string)value, CultureInfo.InvariantCulture);