Update haskell-indentation-indent-line

[fice-t]

Two changes:

1. Some Evil commands are now treated differently to achieve expected
   behaviour.
2. Pressing TAB at the final indent location now starts to move to the
   previous indent position instead of relying on the reindent function to
   start this process.

Fixes #896

[gracjan]

Hmm, I have bad feelings about this. I'm unable to follow the logic neither in the code nor in the test.

1. Hardcoding evil commands is super fragile. Can't we have logic that works properly without this?
2. Can the test be more declarative? I would like to see more tests written in a more declarative manner, for example as a list of tuples: (COMMAND-TO-EXECUTE WHERE-SHOULD-INDENT-END), like this:

    '((indent-right 7)
      (indent-left 12) 
       ...)

That way it would be easier to create more than one scenario.

[fice-t]

The cycle logic is that haskell-indentation-indent-line, on the last tab indent position, moves to the 2nd last indent position (if it exists) on the very first invocation. Before, it only moved on the 2nd call as then it passes control to haskell-indentation-indent-line-repeat.

1. Certainly it's fragile (the this-command part), but I don't really see an obvious better way. We could just set indent-line-function to a new function that does it how Evil commands expect and then bind TAB directly to the old haskell-indentation-indent-line. Might not be the best thing to do though.
2. I suppose. Actually, I think all the test needs is a way to vary the input. So just the source text would be provided.

[geraldus]

Will electric-indent-functions hook be helpful in our case? Looks like haskell-mode totally ignores this.

electric-indent-functions is a variable defined in ‘electric.el’.
Its value is nil

This variable may be risky if used as a file-local variable.

Documentation:
Special hook run to decide whether to auto-indent.
Each function is called with one argument (the inserted char), with
point right after that char, and it should return t to cause indentation,
‘no-indent’ to prevent indentation or nil to let other functions decide.

---

electric-indent-mode is an interactive compiled Lisp function in ‘electric.el’.

(electric-indent-mode &optional ARG)

Toggle on-the-fly reindentation (Electric Indent mode).
With a prefix argument ARG, enable Electric Indent mode if ARG is
positive, and disable it otherwise. If called from Lisp, enable
the mode if ARG is omitted or nil.

When enabled, this reindents whenever the hook ‘electric-indent-functions’
returns non-nil, or if you insert a character from ‘electric-indent-chars’.

This is a global minor mode. To toggle the mode in a single buffer,
use ‘electric-indent-local-mode’.

[gracjan]

O! Nice find!

Maybe we will be able to pacify electric-indent-mode so it works when RET is pressed (or evil-open-below).

[gracjan]

@geraldus: Your comment is priceless for #1133.

[geraldus]

Glad to be helpful! ☀️

[gracjan]

I'm closing this without merging because I think that #1265 is fundamentally better idea.

Thanks for trying, this pr really helped to get the thinking going.