call dhall with "format" argument

[justinwoo]

Set the dhall format subcommand to match the new Dhall arguments

Fix #12

[sellout]

Is it worth keeping any backward compatibility here?

I’d also like to change the type header to use dhall type instead of dhall 2>, so this question applies there as well.

[sellout]

I feel like this should explicitly (cons "format" dhall-format-options) rather than adding "format" to the customizable options.

[psibi]

@sellout Thanks for the review! It would be nice to keep backward compatibility as I myself use an older version yet.

[sellout]

The frustrating bit is that new versions require dhall version and older ones require dhall --version … so it‘s not like we can easily get the answer currently. We need to either just see which command works and dispatch on “new” vs “old” or something like

(or (run-command "dhall version") (run-command "dhall --version"))

and then we can dispatch on the actual version.

Whichever we use, should be defined on its own, so we can use it both for the formatting changes here as well as the type header changes.

[justinwoo]

I'm okay with keeping this PR open for a while or moving it to some specific branch until there's a new proper version released

[purcell]

I made a slightly different change relating to this in 8405e7b - for now, if you set dhall-format-command to nil, the code will use dhall format. This allows us to keep backwards compatibility for now. Later, when the most-used (LTS?) dhall version supports the "format" subcommand, we can flip the default.

[joneshf]

Can that be added to the documentation? It's not clear from reading the current documentation that setting the value to "dhall format" will not work, nor is it clear that setting the value to nil will work the way it's supposed to.

It took finding this issue, and then finding the above comment to understand how this variable is supposed to be used.

[purcell]

Thanks @joneshf - done!

[joneshf]

That's wonderful! Thank you so much!