Please document language formatting capabilities

[Xernisfy]

Today I noticed, that deno fmt was automatically formatting my XML files. (and beautifully at that!)
By default - mind you - not hidden behind a feature/unstable flag.

However, this is not mentioned in deno fmt --help or https://docs.deno.com/runtime/reference/cli/fmt/
Also, the denoland.vscode-deno VSCode extension is not registered as an XML formatter.
I would love to drop my YAML and XML formatter extensions in favor of Deno.

I wonder which other languages/syntaxes are also silently available?
Is this list of feature flags possibly outdated too?

      --unstable-component               Enable formatting Svelte, Vue, Astro and Angular files
      --unstable-css                     Enable formatting CSS, SCSS, Sass and Less files
      --unstable-html                    Enable formatting HTML files
      --unstable-sql                     Enable formatting SQL files.
      --unstable-yaml                    Enable formatting YAML files

I quickly made up some YAML, HTML and CSS files and they were instantly formatted just by deno fmt .

[bartlomieju]

There's https://docs.deno.com/runtime/reference/cli/fmt/#supported-file-types with a table of all supported types and flags required.

[Xernisfy]

True, this table is more up-to-date. HTML, CSS and YAML don't have an unstable flag there.
But XML is not even mentioned but is clearly supported and working.

I guess since XML is not a format often used in Deno, it is not really important to document out-of-scope capabilities.

[bartlomieju]

Thanks for the report. Two things here, and both are now addressed:

1. The stale --unstable-html / --unstable-css / --unstable-yaml flags in --help. These formatters have since been stabilized. In current releases deno fmt --help no longer lists them (only --unstable-component and --unstable-sql remain unstable), and the flags are kept hidden purely for back-compat. So the help text is no longer misleading.

2. XML/SVG formatted by default but undocumented. Confirmed: deno fmt formats .xml and .svg by default (they go through the same markup formatter as HTML, no flag required). I've added them to the supported file types table: docs(fmt): document XML and SVG support in deno fmt docs#3189.

Closing as both the CLI confusion and the documentation gap are resolved. Thanks again!