Change default formatter for any language

[lebakasable]

Idea

Adding an option like this:

[[lang]]
name="yeah"
formatter="youhou" // command to execute when formatting instead of the lsp' default 

Why ?

Because, for example, whe CAN'T format any Zig code with ZLS (just an example 😡)

[the-mikedavis]

This needs a bit of design because currently auto-formatting is only done through the language server. We can't just add a configuration for a formatter binary because it would fight with the language server for any language that has a formatter binary and LSP format.

This probably depends on #1125

[kirawi]

Could we disable the formatting request if a binary is defined for formatting?

[lebakasable]

Yes I think

[slinlee]

This would be great for using prettier which I use for most languages it supports. As @David-Else mentioned in #2182 the commands are like prettier --parser json (the parser needs to be manually set when piping the input vs reading from a file)

[thomas-profitt]

As a workaround, to manually run an external program to reformat the currently-open file in Helix:

1. % to select everything (or only the part you want to reformat)
2. | to pipe the selection to an external program's stdin and replace it with the program's stdout,
3. mix format - (if it's an elixir file, for example)

[kirawi]

I think that what we can do is:

• Add a config option in languages.toml to define a formatter command, and disable LSP formatting requests in Document::format() if a formatter is defined.
• Send the contents of the buffer to the formatter, and use helix-core::diff::compare_ropes() so we can avoid a problem like Auto-format selects entire document #2404.