Functions in Navigation Tables for Power BI Custom Connector

Hi everyone,

I'm building a custom data connector for Power BI, trying to expose a navigation table with a couple of functions, following this specific code sample: https://github.com/microsoft/DataConnectors/blob/master/samples/NavigationTable/NavigationTable.pq#L13. However, even though my function does not accept any parameters, I get a "No parameter values specified" message when trying to import its data in Power BI:

Any idea why? Am I missing something in my code?

Also, I've been wondering whether I could add custom UI to the individual functions by adding the function documentation, however that doesn't seem to be working, either. Is this feature only available for the top-level function of the connector?

For reference, here's the complete implementation of `my TestConnector:

// This file contains your Data Connector logic
[Version = "1.0.0"]
section TestConnector;

TestConnector = [
    Authentication = [
        Anonymous = []
    ]
];

TestConnector.Publish = [
    Beta = true,
    Category = "Other",
    ButtonText = { Extension.LoadString("ButtonTitle"), Extension.LoadString("ButtonHelp") },
    LearnMoreUrl = "https://powerbi.microsoft.com/",
    SourceImage = TestConnector.Icons,
    SourceTypeImage = TestConnector.Icons
];

TestConnector.Icons = [
    Icon16 = { Extension.Contents("TestConnector16.png"), Extension.Contents("TestConnector20.png"), Extension.Contents("TestConnector24.png"), Extension.Contents("TestConnector32.png") },
    Icon32 = { Extension.Contents("TestConnector32.png"), Extension.Contents("TestConnector40.png"), Extension.Contents("TestConnector48.png"), Extension.Contents("TestConnector64.png") }
];

[DataSource.Kind="TestConnector", Publish="TestConnector.Publish"]
shared TestConnector.Contents = () => GetNavigationTable();

GetNavigationTable = () as table =>
    let
        _table = #table(
            { "Name", "Key", "Data", "ItemKind", "ItemName", "IsLeaf" },
            {
                { "Test Function", "func1", Value.ReplaceType(TestFunction, TestFunctionType), "Function", "Function", true },
                { "Another Function", "func2", AnotherFunction.Contents, "Function", "Function", true }
            }
        )
    in
        NavigationTable.FromTable(_table, {"Key"}, "Name", "Data", "ItemKind", "ItemName", "IsLeaf");

TestFunction = (message as text) as table =>
    let
        result = #table(
            { "Column1", "Column2" },
            {{ "Test Function A", message }}
        )
    in
        result;

TestFunctionType = type function (
    message as (type text meta [
        Documentation.FieldCaption = "Message",
        Documentation.FieldDescription = "Parameter description..."
    ])
) as table meta [
    Documentation.Name = "Test Function",
    Documentation.LongDescription = "Function description..."
];

AnotherFunction.Contents = () => "Returns a static string when invoked.";

NavigationTable.FromTable = (_table as table, keyColumns as list, nameColumn as text, dataColumn as text, itemKindColumn as text, itemNameColumn as text, isLeafColumn as text) as table =>
    let
        tableType = Value.Type(_table),
        newTableType = Type.AddTableKey(tableType, keyColumns, true) meta 
        [
            NavigationTable.NameColumn = nameColumn, 
            NavigationTable.DataColumn = dataColumn,
            NavigationTable.ItemKindColumn = itemKindColumn, 
            Preview.DelayColumn = itemNameColumn, 
            NavigationTable.IsLeafColumn = isLeafColumn
        ],
        navigationTable = Value.ReplaceType(_table, newTableType)
    in
        navigationTable;

 Thank you in advance for any suggestions!