Navigator window not displaying function input parameters. Custom Connector for Power BI

[storm-nhaab]

Hi,

I am trying to create a custom connector for Power BI. I have followed the documentation on how to set up

a Navigation Table. The table will navigate to three different functions.

I have set up the code accordingly. However, the UI for the function inputs is not generated in the Navigator window. Rather I am seeing this:

I see the UI just fine in the Power Query Editor. Here is my implementation of some test code:

[DataSource.Kind="PQExtension1", Publish="PQExtension1.Publish"]
shared PQExtension1.Contents = () as table =>
    let
        objects = #table(
            {"Name", "Key", "Data",  "ItemKind", "ItemName", "IsLeaf"},{
            {"Item1", "item1", PQExtension1.GetSeries, "Function", "Function", true}
        }),
        NavTable = Table.ToNavigationTable(objects, {"Key"}, "Name", "Data", "ItemKind", "ItemName", "IsLeaf")
    in
        NavTable;

[DataSource.Kind = "PQExtension1"]
shared PQExtension1.GetSeries = () => Value.ReplaceType(HelloWorldImpl, HelloWorldType)
        

HelloWorldType = type function (
    message as (type text meta [
        Documentation.FieldCaption = "Message",
        Documentation.FieldDescription = "Text to display",
        Documentation.SampleValues = {"Hello world", "Hola mundo"}
    ]),
    optional count as (type number meta [
        Documentation.FieldCaption = "Count",
        Documentation.FieldDescription = "Number of times to repeat the message",
        Documentation.AllowedValues = { 1, 2, 3 }
    ]))
    as table meta [
        Documentation.Name = "Hello - Name",
        Documentation.LongDescription = "Hello - Long Description",
        Documentation.Examples = {[
            Description = "Returns a table with 'Hello world' repeated 2 times",
            Code = "HelloWorldWithDocs.Contents(""Hello world"", 2)",
            Result = "#table({""Column1""}, {{""Hello world""}, {""Hello world""}})"
        ],[
            Description = "Another example, new message, new count!",
            Code = "HelloWorldWithDocs.Contents(""Goodbye"", 1)",
            Result = "#table({""Column1""}, {{""Goodbye""}})"
        ]}
    ];

HelloWorldImpl = (message as text, optional count as number) as table =>
    let
        _count = if (count <> null) then count else 5,
        listOfMessages = List.Repeat({message}, _count),
        table = Table.FromList(listOfMessages, Splitter.SplitByNothing())
    in
        table;

 
I appreciate any help on this. I have seen similar posts here in the Power BI forum but clear solutions have not been given.

[storm-nhaab · Accepted solution]

So I found a solution from the PowerBI REST API connector project. Basically you need a special implementation of the Table.ToNavigationTable function. It seems that you need to delete the "Preview.DelayColumn = itemNameColumn" from Table.ToNavigationTable .

This implementation of the navigation table works:

Table.ForceToNavigationTable = (
    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, 
            NavigationTable.IsLeafColumn = isLeafColumn
        ],
        navigationTable = Value.ReplaceType(table, newTableType)
    in
        navigationTable;

The only problem I have now is that the documentation is not shown in the Navigator window:

In the Power Query Editor it looks like this:

[trello]

Hi, I have a similar problem.

My function has a record type parameter like this

but in the navigation table it looks like this

[v-yiruan-msft]

Hi @storm-nhaab ,

It's glad to hear that your problem has been resolved. And thanks for sharing your solution here. Thank you.

Best Regards

[storm-nhaab]

Hi,

The examples you have given are with functions that does not implement parameters. I have implemented the NavigationTable function from Handling navigation for Power Query connectors | Microsoft Docs. For instance, if I add a parameter to FunctionCallThatReturnATable then I get the same "No Paramters Specified"-Window in the Navigator. Why does the Preview window not allow me to generate the function UI. In the Power Query editor it works just fine.

shared NavigationTable.Simple = () =>
    let
        objects = #table(
            {"Name",       "Key",        "Data",                           "ItemKind", "ItemName", "IsLeaf"},{
            {"Item1",      "item1",      #table({"Column1"}, {{"Item1"}}), "Table",    "Table",    true},
            {"Item2",      "item2",      #table({"Column1"}, {{"Item2"}}), "Table",    "Table",    true},
            {"Item3",      "item3",     (t as text) => FunctionCallThatReturnsATable(t),  "Table",    "Table",    true},            
            {"MyFunction", "myfunction", AnotherFunction.Contents,       "Function", "Function", true}
            }),
        NavTable = Table.ToNavigationTable(objects, {"Key"}, "Name", "Data", "ItemKind", "ItemName", "IsLeaf")
    in
        NavTable;

shared FunctionCallThatReturnsATable = (t as text) =>
    #table({"DynamicColumn"}, {{t}});

[v-yiruan-msft]

Hi @storm-nhaab ,

Please review the following link, hope it can help you.

PowerBIRESTAPI

Best Regards

[storm-nhaab]

Thank you, really appreciate the help! I will check it out.

[v-yiruan-msft]

Hi @storm-nhaab ,

Please refer the following links to get it:

Handling navigation for Power Query connectors | Microsoft Docs

shared NavigationTable.Simple = () =>
    let
        objects = #table(
            {"Name",       "Key",        "Data",                           "ItemKind", "ItemName", "IsLeaf"},{
            {"Item1",      "item1",      #table({"Column1"}, {{"Item1"}}), "Table",    "Table",    true},
            {"Item2",      "item2",      #table({"Column1"}, {{"Item2"}}), "Table",    "Table",    true},
            {"Item3",      "item3",      FunctionCallThatReturnsATable(),  "Table",    "Table",    true},            
            {"MyFunction", "myfunction", AnotherFunction.Contents,       "Function", "Function", true}
            }),
        NavTable = Table.ToNavigationTable(objects, {"Key"}, "Name", "Data", "ItemKind", "ItemName", "IsLeaf")
    in
        NavTable;

shared FunctionCallThatReturnsATable = () =>
    #table({"DynamicColumn"}, {{"Dynamic Value"}});

Custom Connector and Navigation Tables

 GetRows = () => if (state <> null) then state else
                    let
                        list = listFunction(),
                        withName = Table.FromRecords(list, {"Name", "ItemKind", "Parameters"}, MissingField.UseNull),
                        withData = Table.AddColumn(withName, "Data", each dataFunction([Name], [Parameters])),
                        withItemName = Table.AddColumn(withData, "ItemName", each if [Parameters] = null or Record.FieldCount([Parameters]) = 0 then "Table" else null),
                        withoutParameters = Table.RemoveColumns(withItemName, {"Parameters"}),
                        withIsLeaf = Table.AddColumn(withoutParameters, "IsLeaf", each isLeaf),
                        navTable = Table.ToNavigationTable(withIsLeaf, {"Name"}, "Name", "Data", "ItemKind", "ItemName", "IsLeaf")
                    in
                        navTable

Best Regards