[Authoring] Links support only HTTP links

Target Application

Microsoft Teams

Application Operating System

Windows

Schema Version

1.2

Problem Description

When using a uri like file://my/path/to/file or \\my\link\to\fileshare those links are not working. Neither with markdown links nor with url actions.

Expected Outcome

I expect the file share links to open when clicking on them.

Actual Outcome

Nothing happens.

Card JSON

{
"type":"message",
"attachments":[
{
"contentType":"application/vnd.microsoft.card.adaptive",
"contentUrl":null,
"content":{
  "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
  "type": "AdaptiveCard",
  "msteams": { "width":"Full"},
  "version": "1.2",
   "body": [
    {
      {
        "type": "TextBlock",
        "text": "[Open file](\\\\some.fileshare.link\\and\\the\\file\\path.txt)"
      }
    }
  ],
  "actions": [
    {
      "type": "Action.OpenUrl",
      "title": "Open file",
      "url": "file://some.fileshare.link/and/the/file/path.txt"
    }
  ]
}}]}

Repro Steps

Send the card via MS Teams workflow.

Start by locating the Adaptive Cards link-handling entry points for Microsoft Teams and compare markdown links with Action.OpenUrl using the supplied card. Reproduce the file:// and UNC-path cases on Windows; done means both link forms open the referenced file share in Teams, or the unsupported behavior is documented.