Set tabbing to match Elm style guide and examples (2 spaces)

[niksilver]

Problem: When I use elm-vim out of the box it defaults to tab stops of 8 spaces, but the Elm standard is 2 spaces.

Workaround: As a workaround I added the following line to my ~/.vimrc file:

autocmd FileType elm setlocal shiftwidth=2 tabstop=2

But that's a manual change.

Fix: The change submitted seems to fix this problem, and sets tab stops in .elm files to 2 spaces, regardless of the user's global settings.

[dtaskoff]

Where is this "vim standard" defined?
Anyway, such "user-preference" settings should be kept in ~/.vimrc, and elm-format enforces 4 spaces, so elm-vim setting tabstop=2 would be quite inconsistent.

[niksilver]

Regards "standard vim": Yes, "vim standard" is the wrong phrase - the title of the request is an error. I've corrected that now. Apologies for the confusion.

My personal experience suggests that the default tab spacing on most terminals is 8 spaces, and Wikipedia says tab has been "de facto standardized at every multiple of 8 characters horizontally". Therefore as it stands if the elm-vim plugin is installed with no other settings or preferences (user preferences or otherwise) the user can expect to find it defaults to 8-space tabs. This is what I found.

Regards elm-format: I did not suggest tabstop=2 based on elm-format. I suggested it based on looking at the Elm style guide and the code examples on the Elm website. In those examples new indents are 2 spaces, or 4 spaces. Thus I interpret 2 space indents as the base case - the lowest common denominator - and 4 spaces being "2 spaces twice".

Regards user preferences: Yes, user preference settings should indeed be put in ~/.vimrc. However, as the Elm style guide and the examples clearly show a preference, I thought it would be beneficial to users for the Elm plugin to use the "Elm preference" by default. The user can override that if they have a different user preference.

I offer this patch simply as a benefit to the community. The maintainers of ElmCast, of course, are free to accept or reject as they wish.

[dtaskoff]

AFAIK, Evan used two spaces indentation in the examples, since four spaces indentation would make them too wide to fit in the website, and elm-format is supposed to be following (or enforcing) the community preference (since the tool is maintained by members of elm).

I find it confusing, as well, that even the style guide, and the standard packages, are not consistent with regard to indentation (using both two and four spaces).

[andys8]

The majority of projects use elm-format with a non configurable tab width of 4

https://github.com/avh4/elm-format/blob/c14cfb9546144da3b87350944b88849a7dc65dd2/src/Box.hs#L247-L249