Registering a default custom editor, but **not** while in diff mode

[jonathanyeung]

I have an extension that provides a custom editor and registers it as the default editor for markdown files. However, when viewing markdown files in diff mode (such as in the Source Control panel), I want to fall back to using the built-in editor. Two questions:

1. Is it possible for an extension that registers as the default editor for an extension type to not be the default while in diff mode?
2. In case 1 is not possible, is there any UI that allows a user to open a diff view with a particular editor? Something akin to the context menu command Open with... but Open diff with....

package.json:

    "customEditors": [
      {
        "viewType": "my-custom-editor",
        "selector": [
          {
            "filenamePattern": "*.md"
          }
        ],
        "priority": "default"
      }
    ],

Thank you!

[theReynald]

Hi @jonathanyeung.

Here are my thoughts...

1. Different Editor in Diff Mode:

   When you register a custom editor with a priority of default for a specific file type, it will be used in all contexts, including in diff views. From what I know, the VS Code API did not provide an explicit way for a custom editor to specify that it should only be used as the default in certain contexts (like outside of diff views).

2. Open Diff with a Specific Editor:

   VS Code has the "Open with..." context menu which lets users choose a specific editor to open a file. However, there isn't a direct "Open diff with..." counterpart. If a user wants to see the diff in the built-in editor after a custom editor has taken over as the default, they'd have to manually switch the editor after opening the diff view. They can do this by clicking on the ellipsis (...) in the upper right corner of the editor pane and choosing "Switch Editor" to switch back to the built-in markdown viewer. It's a bit cumbersome, but it's a way to get the built-in diff view back.

What you can consider:

1. Educate Users: If you're developing an extension, consider adding notes in your documentation or README to guide users on how to switch between editors, especially if they want to view diffs in the built-in editor.

2. Feature Request: Given your valid use case, it might be a good idea to raise a feature request on the VS Code GitHub repository. The VS Code team is quite responsive, and if they see value and demand for a feature, they often consider implementing it or at least discussing potential solutions.

Hope this helps.

[jonathanyeung]

I found a way that this can be achieved through user settings:

"workbench.editorAssociations": {
    "{git}:/**/*.{md}": "default",
    "*.md": "msharp.customEditor"
},

By adding that line "{git}:/**/*.{md}": "default" - you can get precisely the behavior of using your own custom editor as the default when viewing files, but getting the vs code built-in diff view when viewing the diff from the Source Control tab.

[siegenthalerroger]

Is there a similar way to achieve this for the AI/chat/copilot diff viewer?