我在文件夹内部创建了一个非常简单的.r文件，并希望使用VSCode调试此文件。
以下是采取的步骤：
1.在桌面中创建新文件夹;
1.在新文件夹中创建一个.r文件，并添加简单的R代码;
1.将新文件夹加载到VSCode中并打开.r文件;
1.点击VSCode中的调试图标，创建一个launch.json文件，保存到新建文件夹下的.vscode文件夹中;
1.单击“开始调试”，将显示调试浮动控制窗格，但单步执行/单步执行图标将灰显。
下面是launch.json文件：

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "type": "R-Debugger",
            "name": "Launch R-Workspace",
            "request": "launch",
            "debugMode": "workspace",
            "workingDirectory": "${workspaceFolder}"
        },
        {
            "type": "R-Debugger",
            "name": "Debug R-File",
            "request": "launch",
            "debugMode": "file",
            "workingDirectory": "${workspaceFolder}",
            "file": "${file}"
        },
        {
            "type": "R-Debugger",
            "name": "Debug R-Function",
            "request": "launch",
            "debugMode": "function",
            "workingDirectory": "${workspaceFolder}",
            "file": "${file}",
            "mainFunction": "main",
            "allowGlobalDebugging": false
        },
        {
            "type": "R-Debugger",
            "name": "Debug R-Package",
            "request": "launch",
            "debugMode": "workspace",
            "workingDirectory": "${workspaceFolder}",
            "includePackageScopes": true,
            "loadPackages": [
                "."
            ]
        },
        {
            "type": "R-Debugger",
            "request": "attach",
            "name": "Attach to R process",
            "splitOverwrittenOutput": true
        }
    ]
}

以下是屏幕截图：

为什么单步执行/单步执行图标是灰色的？我无法在当前状态下调试VSCode中的R文件。谢谢。