@bitboxer I use VSCode and switched a few months ago from using GitHub - JakeBecker/vscode-elixir-ls: Elixir language support and debugger for VS Code, powered by ElixirLS. · GitHub to using GitHub - elixir-lsp/vscode-elixir-ls: Elixir language support and debugger for VS Code, powered by ElixirLS. · GitHub

Both of them though enable mix.format on save, if you set this config in your settings.json:

"[elixir]": {
    "editor.formatOnSave": true,
    "editor.defaultFormatter": "elixir-lsp.elixir-ls"
}

I do have persistent odd breakage in formatting though, where at irregular intervals I notice it’s no longer formatting on save, but if I quit VSCode and restart it works again. If anyone has a fix/diagnosis on that I’d love it, mostly because I don’t always notice for a while and occasionally commit unformatted code as a result. It also seems to take a minute or so after restarting to respect the rules for .formatter.exs re: locals_without_parens which often leads to a bunch of changes that I don’t want.