bug#59201: `fill-paragraph' works differently depending on whether Emacs is run in batch mode or not

bug#59201: `fill-paragraph' works differently depending on whether Emacs is run in batch mode or not

[Paul Pogonyshev]

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Tested with Emacs 28 and a recent Emacs 29 build.

To reproduce:

    $ emacs --batch --eval "(princ (with-temp-buffer (insert \"Lorem ipsum
dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna aliqua...\n\") (set-mark 1)
(fill-paragraph nil t) (buffer-string)) 'external-debugging-output)"

Prints the text in one line, i.e. `fill-paragraph' appears to have done
nothing.

If you replace `--batch' in the command line with `-Q' without changing
*anything* else:

    $ emacs -Q --eval "(princ (with-temp-buffer (insert \"Lorem ipsum dolor
sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut
labore et dolore magna aliqua...\n\") (set-mark 1) (fill-paragraph nil t)
(buffer-string)) 'external-debugging-output)"

the output in the console becomes formatted in two lines, i.e.
`fill-paragraph' does its work.

In both cases the code is exactly the same and the function is called
non-interactively. The only difference, as far as I see, is the batch mode.

Paul

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bug#59201: `fill-paragraph' works differently depending on whether Emacs is run in batch mode or not

[Eli Zaretskii]

tags 59201 notabug
thanks

> From: Paul Pogonyshev <pogonyshev@gmail.com>
> Date: Fri, 11 Nov 2022 20:40:25 +0100
> 
>     $ emacs --batch --eval "(princ (with-temp-buffer (insert \"Lorem ipsum dolor sit amet, consectetur
> adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua...\n\") (set-mark 1)
> (fill-paragraph nil t) (buffer-string)) 'external-debugging-output)"
> 
> Prints the text in one line, i.e. `fill-paragraph' appears to have done nothing.
> 
> If you replace `--batch' in the command line with `-Q' without changing anything else:
> 
>     $ emacs -Q --eval "(princ (with-temp-buffer (insert \"Lorem ipsum dolor sit amet, consectetur adipiscing
> elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua...\n\") (set-mark 1) (fill-paragraph nil
> t) (buffer-string)) 'external-debugging-output)"
> 
> the output in the console becomes formatted in two lines, i.e. `fill-paragraph' does its work.
> 
> In both cases the code is exactly the same and the function is called non-interactively. The only difference,
> as far as I see, is the batch mode.

Your program has a bug: it doesn't make sure transient-mark-mode is
turned ON, and it doesn't move point after inserting the text into the
inserted text.  Thus, point is left at EOB, where there's no paragraph
that fill-paragraph can work on.  The doc string of fill-paragraph
says:

  Fill paragraph at or after point.
  [...]
  The REGION argument is non-nil if called interactively; in that
  case, if Transient Mark mode is enabled and the mark is active,
  call ‘fill-region’ to fill each of the paragraphs in the active
  region, instead of just filling the current paragraph.

If you modify the program as follows:

  $ emacs --batch --eval "(princ (with-temp-buffer (insert \"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua...\n\") (goto-char (point-min)) (set-mark 1) (fill-paragraph nil t) (buffer-string)) 'external-debugging-output)"

then the text will be filled in --batch mode as well.

Transient Mark mode is turned on by default only in interactive
sessions, and if you meant fill-region to work on the active region,
then the solution is to modify the program like this:

  $ emacs --batch --eval "(princ (with-temp-buffer (insert \"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua...\n\") (transient-mark-mode 1) (set-mark 1) (fill-paragraph nil t) (buffer-string)) 'external-debugging-output)"

bug#59201: `fill-paragraph' works differently depending on whether Emacs is run in batch mode or not

[Paul Pogonyshev]

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Thanks, please close this then.

Paul

On Sat, 12 Nov 2022 at 12:17, Eli Zaretskii <eliz@gnu.org> wrote:

> tags 59201 notabug
> thanks
>
> > From: Paul Pogonyshev <pogonyshev@gmail.com>
> > Date: Fri, 11 Nov 2022 20:40:25 +0100
> >
> >     $ emacs --batch --eval "(princ (with-temp-buffer (insert \"Lorem
> ipsum dolor sit amet, consectetur
> > adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore
> magna aliqua...\n\") (set-mark 1)
> > (fill-paragraph nil t) (buffer-string)) 'external-debugging-output)"
> >
> > Prints the text in one line, i.e. `fill-paragraph' appears to have done
> nothing.
> >
> > If you replace `--batch' in the command line with `-Q' without changing
> anything else:
> >
> >     $ emacs -Q --eval "(princ (with-temp-buffer (insert \"Lorem ipsum
> dolor sit amet, consectetur adipiscing
> > elit, sed do eiusmod tempor incididunt ut labore et dolore magna
> aliqua...\n\") (set-mark 1) (fill-paragraph nil
> > t) (buffer-string)) 'external-debugging-output)"
> >
> > the output in the console becomes formatted in two lines, i.e.
> `fill-paragraph' does its work.
> >
> > In both cases the code is exactly the same and the function is called
> non-interactively. The only difference,
> > as far as I see, is the batch mode.
>
> Your program has a bug: it doesn't make sure transient-mark-mode is
> turned ON, and it doesn't move point after inserting the text into the
> inserted text.  Thus, point is left at EOB, where there's no paragraph
> that fill-paragraph can work on.  The doc string of fill-paragraph
> says:
>
>   Fill paragraph at or after point.
>   [...]
>   The REGION argument is non-nil if called interactively; in that
>   case, if Transient Mark mode is enabled and the mark is active,
>   call ‘fill-region’ to fill each of the paragraphs in the active
>   region, instead of just filling the current paragraph.
>
> If you modify the program as follows:
>
>   $ emacs --batch --eval "(princ (with-temp-buffer (insert \"Lorem ipsum
> dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
> incididunt ut labore et dolore magna aliqua...\n\") (goto-char (point-min))
> (set-mark 1) (fill-paragraph nil t) (buffer-string))
> 'external-debugging-output)"
>
> then the text will be filled in --batch mode as well.
>
> Transient Mark mode is turned on by default only in interactive
> sessions, and if you meant fill-region to work on the active region,
> then the solution is to modify the program like this:
>
>   $ emacs --batch --eval "(princ (with-temp-buffer (insert \"Lorem ipsum
> dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
> incididunt ut labore et dolore magna aliqua...\n\") (transient-mark-mode 1)
> (set-mark 1) (fill-paragraph nil t) (buffer-string))
> 'external-debugging-output)"
>

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bug#59201: `fill-paragraph' works differently depending on whether Emacs is run in batch mode or not

[Eli Zaretskii]

> From: Paul Pogonyshev <pogonyshev@gmail.com>
> Date: Sat, 12 Nov 2022 12:26:12 +0100
> Cc: 59201@debbugs.gnu.org
> 
> Thanks, please close this then.

Done.