AskForProgramName command did not work

[A2va]

If the try to edit the launch.json file and select Mock Debug: Launch completion. The AskForProgramName dit not fired even, if it's set in the package.json file.

"configurationSnippets": [
  {
    "label": "Mock Debug: Launch",
    "description": "A new configuration for 'debugging' a user selected markdown file.",
    "body": {
      "type": "mock",
      "request": "launch",
      "name": "Ask for file name",
      "program": "${command:AskForProgramName}",
      "stopOnEntry": true
    }
  }
],
"variables": {
  "AskForProgramName": "extension.mock-debug.getProgramName"
}

Or I am missing something ?