Format width option

[cknitt]

Please add an option for configuring the format width (like Reason Language Server had with reason_language_server.format_width).

[amiralies]

what about having this on bsconfig so it's stable across editors / CI scripts.

cc/ @bobzhang @IwanKaramazow

[cknitt]

Yes, that would be even better!

[bobzhang]

@IwanKaramazow does our engine support this under the hood?
If so, what's the primary use case to have such option?

[cknitt]

@bobzhang sorry for answering in place of @IwanKaramazow. 😉

Primary use case - well, different companies/projects/coding conventions use different line widths.
For example, we at CCA have set the line width to 120 in all our JavaScript and Reason projects.

Looking in the syntax repo, it seems to be supported already, see e.g. https://github.com/rescript-lang/syntax/blob/58e1fc9f6c962829ae4934590facc81cb5c9ed58/src/res_printer.mli#L16

[IwanKaramazow]

@bobzhang some more context, the printer uses an algorithm that breaks the layout based on the line width:

// imagine having a line width of 20

// here the total length stays under 20:
apply(arg1, arg2)

// here the total length of 20 is exceeded, so the printer breaks the code over multiple lines
apply(
  arg1,
  arg2,
  arg3,
)

Our engine already supports this under the hood and now defaults to 100.
Different companies use different line widths, e.g. CCA warrants width 120, other companies prefer a width of 80 characters. It makes sense to expose this configuration option longer term, I think. It's hard to pick one line length that is "correct" for everyone…

[cknitt]

@bobzhang As the printer already supports this option, it would be really great if it could be exposed in the next bs-platform release. 🙏

[bobzhang]

The common practice seems to be adding a file like .prettierrc and the formatter respect the config from that file, this looks good to me

[amiralies]

Rescript's formatter is not as customizeable as something like prettier. the only option it has is print width so I'm not sure about introducing a new file like .rescriptfmt. on the other hand if you meant reusing prettier config, this might introduce another ambiguity since prettier is a different tool. my suggestion is putting the option in bsconfig.json or even package.json alongside with a command line flag (bsc -format -width 80 foo.res). what do you think?

[bobzhang]

we may add such -width after we migrate into subcommand mode which will take a while.
bsconfig.json is for build stuff.
Something like .prettierrc seems more future proof since you can add more configurations later

[TheSpyder]

I'm fine with adding a config file that only supports one option initially. Rather than .prettierrc, which might come with expectations the formatter doesn't implement, how about .editorconfig (https://editorconfig.org)? It has a max line length rule that quite a few editors support already.

[amiralies]

editorconfig has a different purpose. My point about not having a separate config file is that personally I don't like rescript's formatter to be much customizable in order to keep a consistent codestyle in community, this is really valuable IMO. If this is a goal of rescript's formatter, chance of having more configs is low. anyway, maybe Iwan is the best person who can answer this.

[TheSpyder]

I don't think it's that different, especially not when editorconfig already has a line length option.

Even if it's a dedicated .resfmt config file with a single option, that would still be better than a command line argument. It has been so difficult over the years to apply a consistent customised refmt to a codebase worked on by multiple people.

personally I don't like rescript's formatter to be much customizable in order to keep a consistent codestyle in community, this is really valuable IMO

I completely agree. I don't think any options other than width should exist. But there was a lot of pressure to add more to refmt so never say never.

[amiralies]

Having a command line option makes it possible to use this option outside of a project. So in an ideal situation both should exist, a command line option and a config file option.

I completely agree. I don't think any options other than width should exist. But there was a lot of pressure to add more to refmt so never say never.

You're right. This might not be valuable for all people.

[imjoshellis]

Are there any updates on this? Anything we can do to help this move forward?

I'd love to be able to configure the break width as I've encountered more than a handful of pipes that are wrapping when I'd prefer them to reformat into multiple lines.