Formatter doesn't work with JSON, Tailwind CSS, and other language modes

[pattobrien]

Describe the bug

I'd like to use deno as the default formatter for all web-related files and languages.

However, not all languages in the formatter docs seem to be supported, and more "fringe" language modes like Post CSS don't seem to be supported either, even though the file has a supported extension (e.g. .css).

I'm not familiar with this part of the VSCode language client / protocol, but since these file extensions do seem to be supported (e.g. when running deno formatter via cli), presumably this should just be as simple as adding JSON, Post CSS and Tailwind CSS as supported formatting languages in this extension.

Steps to Reproduce

In VSCode, when a .css file is identified as either Post CSS or Tailwind CSS language modes, the following error is observed:

FormattingExtension 'Deno' is configured as formatter but it cannot format 'PostCSS'-files

All works fine if the language mode is identified as CSS instead. Similarly, running deno fmt foo.css works fine, even with @tailwind annotations in the file.

Expected behavior

Deno extension should be able to format all extensions / "languages" supported by deno fmt, including .css, .json.

Screenshots

Versions

vscode: 1.96.2 deno: 2.1.4 extension: 3.43.2

[pattobrien]

After some more investigation, when I select deno via Format Document With..., all works fine... I'm not sure if that alludes to this being a VSCode issue, or if there is some further configuration that the deno extension needs to do to register the deno formatter to the file association.

[vicary]

Maybe related to #1170. Since Deno can already format these files, it could be a matter of this extension to report the capability to VS Code.