bug#35254: 27.0.50; cc-mode/electric-pair-mode/electric-layout-mode: bad trailing whitespace behavior in cc-mode

["João Távora" <joaotavora@gmail.com>]

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On Wed, May 15, 2019 at 2:19 PM Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

> > I've just come across the bug myself, and it is indeed annoying.
> > Can you check if this patch, which seems the simplest, serves
> > all purposes?
>
> FWIW, I find it rather ugly (makes the two minor modes too tightly
> intertwined).
>

It's no work of art. But the modes are already intertwined.
(And the code within a mode ain't no work of art, too :-))

> It also adds a test to prevent future regressions
>
> Another approach might be to do the whitespace erasure in
> electric-indent without paying any attention to electric-layout/pair,
> and then in electric-pair to explicitly cause (re)indentation
> after moving point to between the opened pair?
>

Maybe, I don't have time to implement that, and it looks like it
could hold surprises.  But if you do it and it passes the existing
tests and the new one, nothing against


> Yet another option is to tell electric-indent about the final position
> of point and have it refrain from deleting whitespace before that final
> position, as in the patch below.  WDYT?
>

It looks a little like an elaboration of a third abstraction to basically
create another intertwining between e-p-m and e-i-m. Sure it's the
best? Anyway, if it passes all  tests, new and old, great, push it!

(but why are you deleting plainer-c-mode in test/lisp/electric-tests.el?)

João




>
>
>         Stefan
>
>
> diff --git a/lisp/elec-pair.el b/lisp/elec-pair.el
> index 3be09d87b4..a14efff241 100644
> --- a/lisp/elec-pair.el
> +++ b/lisp/elec-pair.el
> @@ -551,7 +551,8 @@ electric-pair-post-self-insert-function
>                           (goto-char pos)
>                           (funcall electric-pair-inhibit-predicate
>                                    last-command-event)))))
> -         (save-excursion (electric-pair--insert pair)))))
> +         (let ((electric-indent--destination (point-marker)))
> +           (save-excursion (electric-pair--insert pair))))))
>        (_
>         (when (and (if (functionp electric-pair-open-newline-between-pairs)
>                        (funcall electric-pair-open-newline-between-pairs)
> diff --git a/lisp/electric.el b/lisp/electric.el
> index 07da2f1d9e..71ebb9cf45 100644
> --- a/lisp/electric.el
> +++ b/lisp/electric.el
> @@ -231,6 +231,14 @@ electric-indent-functions-without-reindent
>  not try to reindent lines.  It is normally better to make the major
>  mode set `electric-indent-inhibit', but this can be used as a
> workaround.")
>
> +(defun electric-indent--inhibited-p ()
> +  (or electric-indent-inhibit
> +      (memq indent-line-function
> +            electric-indent-functions-without-reindent)))
> +
> +(defvar electric-indent--destination nil
> +  "If non-nil, position to which point will be later restored.")
> +
>  (defun electric-indent-post-self-insert-function ()
>    "Function that `electric-indent-mode' adds to `post-self-insert-hook'.
>  This indents if the hook `electric-indent-functions' returns non-nil,
> @@ -272,26 +280,26 @@ electric-indent-post-self-insert-function
>            (when at-newline
>              (let ((before (copy-marker (1- pos) t)))
>                (save-excursion
> -                (unless
> -                    (or (memq indent-line-function
> -                              electric-indent-functions-without-reindent)
> -                        electric-indent-inhibit)
> +                (unless (electric-indent--inhibited-p)
>                    ;; Don't reindent the previous line if the
>                    ;; indentation function is not a real one.
>                    (goto-char before)
>                    (condition-case-unless-debug ()
>                        (indent-according-to-mode)
> -                    (error (throw 'indent-error nil)))
> -                  ;; The goal here will be to remove the trailing
> -                  ;; whitespace after reindentation of the previous line
> -                  ;; because that may have (re)introduced it.
> -                  (goto-char before)
> -                  ;; We were at EOL in marker `before' before the call
> -                  ;; to `indent-according-to-mode' but after we may
> -                  ;; not be (Bug#15767).
> -                  (when (and (eolp))
> -                    (delete-horizontal-space t))))))
> -          (unless (and electric-indent-inhibit
> +                    (error (throw 'indent-error nil))))
> +                ;; The goal here will be to remove the trailing
> +                ;; whitespace after reindentation of the previous line
> +                ;; because that may have (re)introduced it.
> +                (goto-char before)
> +                ;; We were at EOL in marker `before' before the call
> +                ;; to `indent-according-to-mode' but after we may
> +                ;; not be (Bug#15767).
> +                (when (and (eolp)
> +                           ;; Don't delete "trailing space" before point!
> +                           (not (and electric-indent--destination
> +                                     (= (point)
> electric-indent--destination))))
> +                  (delete-horizontal-space t)))))
> +          (unless (and (electric-indent--inhibited-p)
>                         (not at-newline))
>              (condition-case-unless-debug ()
>                  (indent-according-to-mode)
> diff --git a/test/lisp/electric-tests.el b/test/lisp/electric-tests.el
> index 4f1e5729be..0b67fb3f1f 100644
> --- a/test/lisp/electric-tests.el
> +++ b/test/lisp/electric-tests.el
> @@ -876,15 +876,6 @@ electric-layout-for-c-style-du-jour
>        (call-interactively (key-binding `[,last-command-event])))
>      (should (equal (buffer-string) "int main () {\n  \n}"))))
>
> -(define-derived-mode plainer-c-mode c-mode "pC"
> -  "A plainer/saner C-mode with no internal electric machinery."
> -  (c-toggle-electric-state -1)
> -  (setq-local electric-indent-local-mode-hook nil)
> -  (setq-local electric-indent-mode-hook nil)
> -  (electric-indent-local-mode 1)
> -  (dolist (key '(?\" ?\' ?\{ ?\} ?\( ?\) ?\[ ?\]))
> -    (local-set-key (vector key) 'self-insert-command)))
> -
>  (ert-deftest electric-modes-int-main-allman-style ()
>    (ert-with-test-buffer ()
>      (plainer-c-mode)
>
>

-- 
João Távora

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