some changes to expand the usage of custom IFunctionProviders

Author: brettsam

src/WebJobs.Script/Extensions/FunctionMetadataExtensions.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using Microsoft.Azure.WebJobs.Script.Description;
 
 namespace Microsoft.Azure.WebJobs.Script
@@ -62,6 +61,9 @@ public static bool IsDisabled(this FunctionMetadata metadata) =>
         public static bool IsCodeless(this FunctionMetadata metadata) =>
             GetBoolProperty(metadata.Properties, IsCodelessKey);
 
+        public static bool IsCodelessSet(this FunctionMetadata metadata) =>
+            metadata.Properties.ContainsKey(IsCodelessKey);
+
         /// <summary>
         /// Sets a property indicating whether that this function is a direct invoke.
         /// </summary>

src/WebJobs.Script/Host/FunctionMetadataManager.cs

@@ -214,8 +214,11 @@ private void AddMetadataFromCustomProviders(IEnumerable<IFunctionProvider> funct
                             throw new InvalidOperationException($"Found duplicate {nameof(FunctionMetadata)} with the name {metadata.Name}");
                         }
 
-                        // All custom provided functions are considered codeless functions
-                        metadata.SetIsCodeless(true);
+                        // If not explicitly set, consider the function codeless.
+                        if (!metadata.IsCodelessSet())
+                        {
+                            metadata.SetIsCodeless(true);
+                        }
 
                         distinctFunctionNames.Add(metadata.Name);
                         functionMetadataList.Add(metadata);

src/WebJobs.Script/runtimeassemblies.json

@@ -724,15 +724,15 @@
     },
     {
       "name": "System.Collections",
-      "resolutionPolicy": "minorMatchOrLower"
+      "resolutionPolicy": "runtimeVersion"
     },
     {
       "name": "System.Collections.Concurrent",
       "resolutionPolicy": "minorMatchOrLower"
     },
     {
       "name": "System.Collections.Immutable",
-      "resolutionPolicy": "minorMatchOrLower"
+      "resolutionPolicy": "runtimeVersion"
     },
     {
       "name": "System.Collections.NonGeneric",
@@ -1136,7 +1136,7 @@
     },
     {
       "name": "System.Runtime",
-      "resolutionPolicy": "minorMatchOrLower"
+      "resolutionPolicy": "runtimeVersion"
     },
     {
       "name": "System.Runtime.CompilerServices.VisualC",