bug#32496: 27.0.50; Strange indentation when ruby-align-chained-calls is t

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Lars Ingebrigtsen [2021-09-02 08:55:50] wrote:

> "Bozhidar Batsov" <bozhidar@batsov.dev> writes:
>
>> Ah, I finally understood the issue at hand! It's really hard to discuss
>> indentation problems in e-mail. :D
>>
>> Yeah, I can confirm there's a bug when using (setq ruby-align-chained-calls t)
>> in this example:
>>
>> some_variable.where.not(x: nil)
>>                    .where(y: 2)
>>
>> The two `where`s should be lined up, but currently the second `where` is
>> lined up with the `not`.
>
> So this is coming from:
>
>     ('(:before . ".")
>      (if (smie-rule-sibling-p)
>          (and ruby-align-chained-calls 0)
>        (smie-backward-sexp ".")
>        (cons 'column (+ (current-column)
>                         ruby-indent-level))))
>
> In the aligned case, I think we should back up to the first "." in the
> chain and use that as the column?  But my SMIE-fu is pretty much
> non-existent, so I've added Stefan to the CCs.

You could try something like

    diff --git a/lisp/progmodes/ruby-mode.el b/lisp/progmodes/ruby-mode.el
    index c09f007a5ee..c681800f6a7 100644
    --- a/lisp/progmodes/ruby-mode.el
    +++ b/lisp/progmodes/ruby-mode.el
    @@ -640,7 +640,15 @@ ruby-smie-rules
         ('(:before . "do") (ruby-smie--indent-to-stmt))
         ('(:before . ".")
          (if (smie-rule-sibling-p)
    -         (and ruby-align-chained-calls 0)
    +         (when ruby-align-chained-calls
    +           (while
    +               (let ((pos (point))
    +                     (parent (smie-backward-sexp ".")))
    +                 (if (not (equal (nth 2 parent) "."))
    +                     (progn (goto-char pos) nil)
    +                   (goto-char (nth 1 parent))
    +                   (not (smie-rule-bolp)))))
    +           (cons 'column (current-column)))
            (smie-backward-sexp ".")
            (cons 'column (+ (current-column)
                             ruby-indent-level))))
    @@ -826,13 +834,6 @@ ruby--electric-indent-p
     
     ;; FIXME: Remove this?  It's unused here, but some redefinitions of
     ;; `ruby-calculate-indent' in user init files still call it.
    -(defun ruby-current-indentation ()
    -  "Return the indentation level of current line."
    -  (save-excursion
    -    (beginning-of-line)
    -    (back-to-indentation)
    -    (current-column)))
    -
     (defun ruby-indent-line (&optional ignored)
       "Correct the indentation of the current Ruby line."
       (interactive)

But please add corresponding regression tests,


        Stefan