haskell-cabal-subsection-arrange-lines should take in account comments

[geraldus]

This is a tricky case I want to discuss. Consider following dependencies list of scaffolded Yesod application with three extra dependencies I've added manually at the end:

    build-depends: base                          >= 4          && < 5
                 , yesod                         >= 1.4.1      && < 1.5
                 …
                 , classy-prelude                >= 0.10.2
                 …
                 , template-haskell
                 …
                 , unordered-containers
                 , containers
                 , vector
                 , time
                 -- extra
                 , lambdacms-core
                 , blaze-html
                 , wai

Now if I run haskell-cabal-subsection-arrange-lines it becomes:

    build-depends: aeson                         >= 0.6        && < 0.10
                 , base                          >= 4          && < 5
                 …
                 , yesod-static                  >= 1.4.0.3    && < 1.6
                 -- extra
                 , lambdacms-core
                 , blaze-html
                 , wai

So, as you can see, everything till comment is rearranged as expected, but lines after comment leaved untouched. It is not matter where the point stands when re-arrange command is executed, the result is the same. In my current case I used comment to split dependency list into sections, but others can place comments for other needs. So, in my current case I expect the second section would be sorted independently of first one leaving comment as section separator (there is an easy way — wrap second section by region and call sort-lines).

Definitely it would be better if haskell-cabal-subsection-arrange-lines to sort whole list, but it's not clear how to deal with comments. I can think of few scenarios:

• leave current behaviour: sort list until first comment
• sort everything, move comments at the end of the list
• sort comment lines with dependencies, there are at least two options:
  • assume comments are related to previous lines
  • assume comments are related to following lines
• sort whole list by subsecions, where comment are assumed as subsection delimiters

I think all this scenarios could be covered by some optional parameter, defaulting to current behaviour.

What do you think?

[gracjan]

This is relevant:

https://github.com/haskell/cabal/issues/2681

[gracjan]

@geraldus: Your example is better formatted like this:

    -- standard dependencies
    build-depends: base                          >= 4          && < 5
                 , yesod                         >= 1.4.1      && < 1.5
                 …
                 , classy-prelude                >= 0.10.2
                 …
                 , template-haskell
                 …
                 , unordered-containers
                 , containers
                 , vector
                 , time

    -- extra dependencies
    build-depends: lambdacms-core
                 , blaze-html
                 , wai

Then C-c C-s can format whole value as is.

[geraldus]

@gracjan indeed! I didn't know it is allowed to have several build-depends sections, thanks! Ok, let's discuss "comments as comments" cases in this case.

[bergey]

My preference would be:

• comments starting a line are section separators
• comments after other text are kept with that line

I think that captures the styles I see most often. But obviously we can't support all possible styles, so I'm fine with whatever you decide to implement. If you decide not to treat comments as section separators, I have a slight preference for comments describing the following line.