Cell formatting doesn't respect dependencieslocals_without_parens

[sabiwara]

Environment

• Elixir & Erlang/OTP versions (elixir --version): 1.13.4 / OTP 25
• Operating system: MacOS
• How have you started Livebook (mix phx.server, livebook CLI, Docker, etc): escript
• Livebook version (use git rev-parse HEAD if running with mix): 0.6.1
• Browsers that reproduce this bug (the more the merrier): Firefox
• Include what is logged in the browser console: -
• Include what is logged to the server console: -

Current behavior

Adding ecto and input the following query:

from f in "foo", select: f.name

Run the formatter:

It added parentheses despite locals_without_parens.

Expected behavior

Do not add parentheses for macros specified in locals_without_parens.

I'm happy to have a look and try to open a PR if this is something we want to address.

[josevalim]

I think this is hard because we would need to list somewhere the dependencies we want to include on the formatting. @jonatanklosko who does the formatting? Livebook or the runtime? If Livebook, then it is not possible at all and we should close this as not possible. :(

[jonatanklosko]

@josevalim it's the runtime, is there an easy way for us to get all dependency formatting rules, without specifying them explicitly?

[sabiwara]

It seems currently this is done in the Mix.Tasks.Format, but it doesn't seem to be a public API to retrieve this?
https://github.com/elixir-lang/elixir/blob/main/lib/mix/lib/mix/tasks/format.ex#L357-L365=

[jonatanklosko]

Unfortunately it's not trivial, when using Mix.install there's currently no easy way to locate dependencies, because Mix.Project.deps_paths() doesn't work. This would most likely require changes to Elixir, so we can wait until there's a stronger indicator we need this :)

[zachdaniel]

We're using Livebook for things like Ash tutorials, and for Ash.Resource and friends, locals_without_parens is a pretty important aspect in keeping the code readable. Basically all of our tutorials can't be edited in the Livebook directly because saving it will overwrite the formatting, which takes a few minutes of work to address, and is very easy to accidentally do since it of course feels natural to edit the livebook.

I wouldn't mind if special config needs to be set in the setup to make this work, like
Application.put_env(:livebook, :formatter, import_deps: [:ash, ...])

[jonatanklosko]

@josevalim perhaps if we made Mix.in_install_dir public (or another specific function), we could get the formatter config from all deps. I will experiment with this later!

[jonatanklosko]

@zachdaniel we decided to disable formatting on-save altogether (#2605).