GNU bug report logs - #78519
30.0.91; In Gnus, when yanking an article, all its newlines become soft

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Mekeor Melire <mekeor <at> posteo.de>, Eric Abrahamsen <eric <at> ericabrahamsen.net>
Cc: 78519 <at> debbugs.gnu.org
Subject: bug#78519: 30.0.91; In Gnus, when yanking an article, all its newlines become soft
Date: Sat, 24 May 2025 12:37:36 +0300

> From: Mekeor Melire <mekeor <at> posteo.de>
> Date: Tue, 20 May 2025 22:50:21 +0000
> 
> GNU Emacs and Gnus support RFC 3676 (obsoleting RFC 2646) “The
> Text/Plain Format and DelSp Parameters” as described in (info
> "(emacs-mime) Flowed text"). But when replying to an article, or
> more specifically, when yanking an article (no matter whether it's
> Fixed or Flowed) while composing a message, all yanked newlines
> become soft newlines, or more specifically, no newline has the
> text-property `hard' set to t. As a consequence, when the composed
> message is sent with Format=Flowed, it will be encoded wrongly and
> its readers will see it terribly displayed.
> 
> 
> How to arrive at this misbehavior?
> ==================================
> 
> 1. Open an article of content-type text/plain with Gnus. Gnus
> decodes and inlines the article. If the article has the Format
> MIME-parameter set to Flowed, the function `mm-inline-text'
> inlines the article and refills it to the column specified per
> `fill-flowed-display-column' variable by calling
> `fill-flowed'. `fill-flowed' itself can tell which newlines are
> soft and which are hard because they are respectively present as
> either as the sequence SPC CRLF, or just CRLF without preceding
> SPC. But after `fill-flowed' is called, both types of newlines are
> just CRLF and even without any text-property.
> 
> 2. Start composing a reply to the article, e.g. by pressing R,
> bound `gnus-article-reply-with-original' in
> `gnus-article-mode-map'. Gnus will set up a compose buffer and
> yank the original article with citation prefix. Yanking happens by
> first calling `gnus-copy-article-buffer', which copies the
> original article, from the buffer where it is displayed and read,
> to the new composing message buffer while removing all
> text-properties. (Then, yanking will continue by adding the
> citation prefixes.) The resulting buffer has only soft newlines.
> 
> A. Note that this behavior is only a bug if the composed reply has
> Format parameter set to Flowed, which Emacs decides to do if at
> least once in the buffer, the text-property `hard' is set to
> t. See “On encoding text, regardless of ‘use-hard-newlines’, lines
> terminated by soft newline characters are filled together and
> wrapped” at (info "(emacs-mime) Flowed text") and the form (setq
> use-hard-newlines (text-property-any (point-min) (point-max) 'hard
> 't)) in definition of function `mml-generate-mime-1' [2].
> 
> 
> What would be the correct behavior?
> ===================================
> 
> X. In my opinion, we should retain the property that it makes no
> difference in effect between first turning on `use-hard-newlines'
> and then yanking, or the other way around.
> 
> Y. In my opinion, we should continue to use the `hard'
> text-property on hard newlines in the composing buffer, because
> most filling related commands know about it.
> 
> Z. In my opinion, when yanking a Fixed formatted article, all
> yanked newlines should become hard or rather be interpreted as
> hard, i.e. they should get the `hard' text-property set to t. This
> is because it's hard to tell if we can interpret a newline as soft
> newline, or if it's really meant to be hard, e.g. because it's a
> poem. [3]
> 
> Thus, I think that yanking hard newlines from Format=Flowed
> articles should have `hard' set to t in the compose
> buffer. Similarly, any newline yanked from a Fixed [4] article
> should have `hard' set to t as well. And the detection described
> at (A.), whether Format parameter should be set to Fixed for the
> composing message, should be changed, so that it only checks
> whether `use-hard-newlines' is non-nil rather than looking for any
> `hard' property set to t, because this would conflict with (X.).
> 
> 
> How can we approach the proposed correct behavior?
> ==================================================
> 
> α. Let's fix `fill-flowed' so that it sets `hard' to t on hard
> newlines after refilling. Please find attached a patch for this.
> 
> β. Let's fix `gnus-copy-article-buffer' so that it keeps `hard'
> text-properties on newlines. Please find attached a patch for
> this. I'm not sure if it suffices to fix this function, because we
> want the `hard' propertized hard newlines in many cases:
> 
>   - Content-Type text/plain, without any Format specification; or
>     with Format specification set to Fixed or Flowed
>   - Content-Type multipart/* where for each text/plain part we
>     want proper hard newlines.
> 
> γ. Let's fix (Z) but I'm yet sure how.
> 
> 
> Footnotes
> =========
> 
> [2] Oops, in my init.el, I have configured
>     `message-citation-line-format' to contain a `hard-newline. I
>     guess, all my sent reply-messages have Format=Flowed?
> 
> [3] There might be approximating heuristics for this. But what'd
>     be more important is to provide users commands so that they
>     can convert hard and soft newlines within a region or
>     paragraph back and forth, as desired. But that's future work.
> 
> [4] Be it Fixed by explicitly setting Format=Fixed, or by omitting
>     the Format parameter completely.

Eric, any comments?

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