How can I setup auto-formatting on save with Helix?

[elijahblackmore]

I am on Helix version 23.10, and I have installed the CLI via brew install biome. I have also ran biome init in the project directory, so I should have a valid biome.json file in-case that is required.

As per these instructions, I have copied these lines into my languages.toml file:

[language-server]
biome = { command = "biome", args = ["lsp-proxy"] }

[[language]]
name = "jsx"
language-servers = [ { name = "typescript-language-server", except-features = [ "format" ] }, "biome" ]
auto-format = true

[[language]]
name = "js"
language-servers = [ { name = "typescript-language-server", except-features = [ "format" ] }, "biome" ]
auto-format = true

Linting appears to be working correctly, but there isn't any formatting on save. I can run the command biome format --write <file> to format, and perhaps there is a way to integrate this command using the formatter key, but I haven't figured out a working solution yet.

typescript-language-server seems to have its own formatter, which I'm assuming is the case with Biome, and I shouldn't need to add something like formatter = { command = "prettier", args = ["--parser", "typescript"] } which is what I used for Prettier.

Am I doing something horribly wrong here? This is my first time using this, and I'm not well versed in configuring languages for Helix. Any pointers would be greatly appreciated!

[elijahblackmore]

Adding the following line solved this:

formatter = { command = "biome", args = ["format", "--stdin-file-path", "test.js"] }

[janos-r]

Not clear why a file name is needed, but yes, I also got it working thanks to this explanation. The docs should definitely be updated. I found this thread through an old post on the discord.

the relevant lines in my config:

[language-server]
biome = { command = "biome", args = ["lsp-proxy"] }

[[language]]
name = "typescript"
auto-format = true
language-servers = [
  { name = "typescript-language-server", except-features = [
    "format",
  ] },
  "biome",
]
formatter = { command = "biome", args = [
  "format",
  "--stdin-file-path=prd.js", # no idea why a file name is needed
  "--indent-style=space",
  "--indent-width=4",
] }

[ematipico]

Not clear why a file name is needed

It's needed because Biome needs to know what language you're passing, which is something isn't possible to infer from content only. Biome will use the file name extension to infer the file type, and apply the correct formatting. This becomes even more crucial with a formatter that supports multiple languages

This is what Prettier does too.