Include also null entries as empty when building InvocationRequest payload for OOP workers (#8989)

* Include also null entries as empty when building InvocationRequest payload for OOP workers

* Better comment on explaining the ?? string.Empty

Co-authored-by: Wessel Kranenborg <[email protected]>

Author: kshyju

src/WebJobs.Script.Grpc/MessageExtensions/GrpcMessageConversionExtensions.cs

@@ -301,19 +301,14 @@ internal static TypedData ToRpcStringArray(this string[] arrString, bool include
             CollectionString collectionString = new CollectionString();
             foreach (string element in arrString)
             {
-                // Don't add null entries.("Add" method below will throw)
-                if (element is null)
+                // Empty string/null entries are okay to add based on includeEmptyEntries param value.
+                if (string.IsNullOrEmpty(element) && !includeEmptyEntries)
                 {
                     continue;
                 }
 
-                // Empty string entries are okay to add based on includeEmptyEntries param value.
-                if (element == string.Empty && !includeEmptyEntries)
-                {
-                    continue;
-                }
-
-                collectionString.String.Add(element);
+                // Convert null entries to emptyEntry because "Add" method doesn't support null (will throw)
+                collectionString.String.Add(element ?? string.Empty);
             }
             typedData.CollectionString = collectionString;
 

test/WebJobs.Script.Tests/Workers/Rpc/GrpcMessageConversionExtensionsTests.cs

@@ -503,7 +503,7 @@ public async Task ToRpc_Collection_String_IgnoreEmptyEntries_When_Capability_Is_
         }
 
         [Fact]
-        public async Task ToRpc_Collection_String_IncludeEmptyEntries_When_Capability_Is_Present()
+        public async Task ToRpc_Collection_String_IncludeEmptyAndNullEntries_When_Capability_Is_Present()
         {
             var logger = MockNullLoggerFactory.CreateLogger();
             var capabilities = new GrpcCapabilities(logger);
@@ -516,7 +516,7 @@ public async Task ToRpc_Collection_String_IncludeEmptyEntries_When_Capability_Is
             string[] arrString = { "element1", string.Empty, "element_2", null };
             TypedData actual = await arrString.ToRpc(logger, capabilities);
 
-            var expected = new RepeatedField<string> { "element1", string.Empty, "element_2" }; // null entry should be still skipped
+            var expected = new RepeatedField<string> { "element1", string.Empty, "element_2", string.Empty }; // null entry should be converted to string.Empty because collection doesn't support null's
             Assert.Equal(expected, actual.CollectionString.String);
         }