Power BI自定义连接器导航表函数报错及UI定制问题咨询

报错“未指定参数值”的核心原因是导航表中的无参数函数未绑定正确的类型元数据，Power BI无法识别它是无参数函数，因此默认弹出参数输入框。

你的代码中，AnotherFunction.Contents是无参数函数，但在导航表的Data列直接传入了函数本身，没有像TestFunction那样通过Value.ReplaceType绑定明确的函数类型。Power BI需要通过类型元数据判断函数的参数数量和类型。

解决步骤： #

1. 为无参数函数定义明确的类型（可同时添加文档元数据）：

AnotherFunctionType = type function () as text meta [
    Documentation.Name = "Another Function",
    Documentation.LongDescription = "Returns a static string when invoked."
];

2. 在导航表的Data列，用Value.ReplaceType绑定该类型：

{ "Another Function", "func2", Value.ReplaceType(AnotherFunction.Contents, AnotherFunctionType), "Function", "Function", true }

函数文档并非仅适用于顶级函数，导航表中的函数也能生效，你的问题是未给所有函数绑定带文档元数据的类型。

TestFunction虽然绑定了类型，但需要确保类型定义的元数据正确；而AnotherFunction之前没有绑定任何类型，自然无法显示文档。只要给导航表中的函数都绑定包含Documentation元数据的类型，就能触发自定义UI和文档展示。

// 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", Value.ReplaceType(AnotherFunction.Contents, AnotherFunctionType), "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.";

AnotherFunctionType = type function () as text meta [
    Documentation.Name = "Another Function",
    Documentation.LongDescription = "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, 
            NavigationTable.ItemNameColumn = itemNameColumn, 
            NavigationTable.IsLeafColumn = isLeafColumn
        ],
        navigationTable = Value.ReplaceType(_table, newTableType)
    in
        navigationTable;

注：修正了NavigationTable.FromTable中的元数据配置，将原Preview.DelayColumn改为标准的NavigationTable.ItemNameColumn，避免潜在的预览异常。

内容的提问来源于stack exchange，提问作者Petr Broz