GNU bug report logs - #73206
28.2; xml comment with blank lines to do not indent correctly, nxml-mode.el

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: John Ciolfi <ciolfi <at> mathworks.com>
To: <bug-gnu-emacs <at> gnu.org>
Subject: 28.2; xml comment with blank lines to do not indent correctly,
 nxml-mode.el
Date: Thu, 12 Sep 2024 13:53:26 -0400

[Message part 1 (text/plain, inline)]

1. Create foo.xml containing:

<foo>
    <!--
        foo

bar
    -->
</foo>

Notice that we have a blank line in the xml comment.

2. Put the point on 'bar' and press TAB.

Notice that the 'bar' line is not indented correctly.

Solution
--------

The problem is that in nxml-compute-indent-in-delimited-token, there
is a (forward-line -1) which assumes that the prior line is indented. In
this case the prior line is a blank line and thus doesn't have
indentation. After the (forward-line -1), we need to keep going back
until we see a non-blank line:

 	   (forward-line -1)
+           (while (looking-at "^[:blank:]*$")
+	     (forward-line -1))

Attached is a patch for nxml-mode.el that fixes the issue. 

Thanks
John

In GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38, cairo version 1.16.0)
 of 2024-06-25, modified by Debian built on x86-conova-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12101006
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[nxml-mode.el.patch (text/x-diff, inline)]

--- ./orig/nxml-mode.el	2024-09-12 09:10:46.580451579 -0400
+++ nxml-mode.el	2024-09-12 09:04:48.473571128 -0400
@@ -1522,6 +1522,8 @@
 	((progn
 	   (goto-char pos)
 	   (forward-line -1)
+           (while (looking-at "^[:blank:]*$")
+	     (forward-line -1))
 	   (<= (point) xmltok-start))
 	 (goto-char (+ xmltok-start (length open-delim)))
 	 (when (and (string= open-delim "<!--")

Message #8 received at 73206 <at> debbugs.gnu.org (full text, mbox):

From: Robert Pluim <rpluim <at> gmail.com>
To: 73206 <at> debbugs.gnu.org
Cc: ciolfi <at> mathworks.com
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent
 correctly, nxml-mode.el
Date: Fri, 13 Sep 2024 09:43:09 +0200

>>>>> On Thu, 12 Sep 2024 13:53:26 -0400, John Ciolfi via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org> said:

    John> 1. Create foo.xml containing:

    John> <foo>
    John>     <!--
    John>         foo

    John> bar
    --> 
    John> </foo>

    John> Notice that we have a blank line in the xml comment.

    John> 2. Put the point on 'bar' and press TAB.

    John> Notice that the 'bar' line is not indented correctly.

    John> Solution
    John> --------

    John> The problem is that in nxml-compute-indent-in-delimited-token, there
    John> is a (forward-line -1) which assumes that the prior line is indented. In
    John> this case the prior line is a blank line and thus doesn't have
    John> indentation. After the (forward-line -1), we need to keep going back
    John> until we see a non-blank line:

    John>  	   (forward-line -1)
    John> +           (while (looking-at "^[:blank:]*$")
    John> +	     (forward-line -1))
 
    John> Attached is a patch for nxml-mode.el that fixes the issue. 

Your patch does the right thing, but for the wrong reasons. Regexp
character classes only have meaning with a bracket expression, so what
youʼre matching here is actually any lines containing zero or more of
':', 'b', 'l', 'a', 'n', or 'k'. IOW, you should use:

     (looking-at "^[[:blank:]]*$")

Robert
-- 

Message #11 received at 73206 <at> debbugs.gnu.org (full text, mbox):

From: John Ciolfi <ciolfi <at> mathworks.com>
To: Robert Pluim <rpluim <at> gmail.com>, "73206 <at> debbugs.gnu.org"
 <73206 <at> debbugs.gnu.org>
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent
 correctly, nxml-mode.el
Date: Sun, 15 Sep 2024 12:08:17 +0000

[Message part 1 (text/plain, inline)]

Thanks for catching my typo and for moving the fix along.
________________________________
From: Robert Pluim <rpluim <at> gmail.com>
Sent: Friday, September 13, 2024 3:43 AM
To: 73206 <at> debbugs.gnu.org <73206 <at> debbugs.gnu.org>
Cc: John Ciolfi <ciolfi <at> mathworks.com>
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent correctly, nxml-mode.el

>>>>> On Thu, 12 Sep 2024 13:53:26 -0400, John Ciolfi via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org> said:

    John> 1. Create foo.xml containing:

    John> <foo>
    John>     <!--
    John>         foo

    John> bar
    -->
    John> </foo>

    John> Notice that we have a blank line in the xml comment.

    John> 2. Put the point on 'bar' and press TAB.

    John> Notice that the 'bar' line is not indented correctly.

    John> Solution
    John> --------

    John> The problem is that in nxml-compute-indent-in-delimited-token, there
    John> is a (forward-line -1) which assumes that the prior line is indented. In
    John> this case the prior line is a blank line and thus doesn't have
    John> indentation. After the (forward-line -1), we need to keep going back
    John> until we see a non-blank line:

    John>           (forward-line -1)
    John> +           (while (looking-at "^[:blank:]*$")
    John> +          (forward-line -1))

    John> Attached is a patch for nxml-mode.el that fixes the issue.

Your patch does the right thing, but for the wrong reasons. Regexp
character classes only have meaning with a bracket expression, so what
you’re matching here is actually any lines containing zero or more of
':', 'b', 'l', 'a', 'n', or 'k'. IOW, you should use:

     (looking-at "^[[:blank:]]*$")

Robert
--

[Message part 2 (text/html, inline)]

Message #14 received at 73206 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: John Ciolfi <ciolfi <at> mathworks.com>, Stefan Kangas <stefankangas <at> gmail.com>
Cc: 73206 <at> debbugs.gnu.org, rpluim <at> gmail.com
Subject: Re: bug#73206: 28.2;
 xml comment with blank lines to do not indent correctly, nxml-mode.el
Date: Sat, 28 Sep 2024 11:45:46 +0300

Stefan, does the patch with the regexp fix look correct to you?

> Date: Sun, 15 Sep 2024 12:08:17 +0000
> msip_labels: 
> From:  John Ciolfi via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
> 
> Thanks for catching my typo and for moving the fix along.
> -----------------------------------------------------------------------------
> From: Robert Pluim <rpluim <at> gmail.com>
> Sent: Friday, September 13, 2024 3:43 AM
> To: 73206 <at> debbugs.gnu.org <73206 <at> debbugs.gnu.org>
> Cc: John Ciolfi <ciolfi <at> mathworks.com>
> Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent correctly, nxml-mode.el 
>  
> >>>>> On Thu, 12 Sep 2024 13:53:26 -0400, John Ciolfi via "Bug reports for GNU Emacs, the Swiss army
> knife of text editors" <bug-gnu-emacs <at> gnu.org> said:
> 
>     John> 1. Create foo.xml containing:
> 
>     John> <foo>
>     John>     <!--
>     John>         foo
> 
>     John> bar
>     --> 
>     John> </foo>
> 
>     John> Notice that we have a blank line in the xml comment.
> 
>     John> 2. Put the point on 'bar' and press TAB.
> 
>     John> Notice that the 'bar' line is not indented correctly.
> 
>     John> Solution
>     John> --------
> 
>     John> The problem is that in nxml-compute-indent-in-delimited-token, there
>     John> is a (forward-line -1) which assumes that the prior line is indented. In
>     John> this case the prior line is a blank line and thus doesn't have
>     John> indentation. After the (forward-line -1), we need to keep going back
>     John> until we see a non-blank line:
> 
>     John>           (forward-line -1)
>     John> +           (while (looking-at "^[:blank:]*$")
>     John> +          (forward-line -1))
>  
>     John> Attached is a patch for nxml-mode.el that fixes the issue. 
> 
> Your patch does the right thing, but for the wrong reasons. Regexp
> character classes only have meaning with a bracket expression, so what
> you’re matching here is actually any lines containing zero or more of
> ':', 'b', 'l', 'a', 'n', or 'k'. IOW, you should use:
> 
>      (looking-at "^[[:blank:]]*$")
> 
> Robert
> -- 

Message #17 received at 73206 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>, John Ciolfi <ciolfi <at> mathworks.com>
Cc: 73206 <at> debbugs.gnu.org, rpluim <at> gmail.com
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent
 correctly, nxml-mode.el
Date: Sun, 29 Sep 2024 13:47:44 -0700

Eli Zaretskii <eliz <at> gnu.org> writes:

> Stefan, does the patch with the regexp fix look correct to you?

If we want to "keep going back until we see a non-blank line", surely
the fragment should read:

    (while (looking-at "^$")
      (forward-line -1))

Since

    (looking-at "^[[:blank:]]*$")

will match both blank lines, and lines containing only blank space.

Which of the two do we want here?

I think it would also be good to add one or more tests here.

Message #20 received at 73206 <at> debbugs.gnu.org (full text, mbox):

From: John Ciolfi <ciolfi <at> mathworks.com>
To: Stefan Kangas <stefankangas <at> gmail.com>, Eli Zaretskii <eliz <at> gnu.org>
Cc: "73206 <at> debbugs.gnu.org" <73206 <at> debbugs.gnu.org>,
 "rpluim <at> gmail.com" <rpluim <at> gmail.com>
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent
 correctly, nxml-mode.el
Date: Wed, 2 Oct 2024 11:59:03 +0000

[Message part 1 (text/plain, inline)]

Hi

Using "^$" or "^[[:blank:]]*$" is fine. The difference is very minor. Consider foo.xml where the visibly "empty" line contains a single space and foo starts on the 1st column:

<foo>
  <!--
      bar

foo
  -->
</foo>

When using "^$" and you type tab on the foo line, you'll get the following where foo starts on the 2nd column:

<foo>
  <!--
      bar

 foo
  -->
</foo>

If you use "^[[:blank:]]*$, you'll get what I expected:

<foo>
  <!--
      bar

      foo
  -->
</foo>

However, if you select all and indent-region, C-M-\ on the original you'll get the expected result with either "^$" or "^[[:blank:]]*$ because nxml-mode will pad out the space line. If the "empty" line truly blank (no spaces or tabs), then the two regex's behave identical.

I suggest for test cases, two versions of foo.xml where one version of it has the empty line truly blank (no spaces or tabs) and the other version contains a space in the "empty" line.

You can use the attached nxml-mode-indent-fix.el which overrides the broken function to try things out on a stock Emacs, emacs -Q.

Thanks
John


________________________________
From: Stefan Kangas <stefankangas <at> gmail.com>
Sent: Sunday, September 29, 2024 4:47 PM
To: Eli Zaretskii <eliz <at> gnu.org>; John Ciolfi <ciolfi <at> mathworks.com>
Cc: rpluim <at> gmail.com <rpluim <at> gmail.com>; 73206 <at> debbugs.gnu.org <73206 <at> debbugs.gnu.org>
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent correctly, nxml-mode.el

Eli Zaretskii <eliz <at> gnu.org> writes:

> Stefan, does the patch with the regexp fix look correct to you?

If we want to "keep going back until we see a non-blank line", surely
the fragment should read:

    (while (looking-at "^$")
      (forward-line -1))

Since

    (looking-at "^[[:blank:]]*$")

will match both blank lines, and lines containing only blank space.

Which of the two do we want here?

I think it would also be good to add one or more tests here.

[Message part 2 (text/html, inline)]

[nxml-mode-indent-fix.el (text/x-emacs-lisp, attachment)]

Message #23 received at 73206 <at> debbugs.gnu.org (full text, mbox):

From: John Ciolfi <ciolfi <at> mathworks.com>
To: Stefan Kangas <stefankangas <at> gmail.com>, Eli Zaretskii <eliz <at> gnu.org>
Cc: "73206 <at> debbugs.gnu.org" <73206 <at> debbugs.gnu.org>,
 "rpluim <at> gmail.com" <rpluim <at> gmail.com>
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent
 correctly, nxml-mode.el
Date: Wed, 30 Apr 2025 10:55:07 +0000

[Message part 1 (text/plain, inline)]

Hi

I see this bug isn't fixed in Emacs 30. Is it possible to fix? The right solution is to update nxml-compute-indent-in-delimited-token to contain "(while (looking-at "^[[:blank:]]*$") (forward-line -1))" to obtain the correct indentation level for text in xml comments when there's blank lines.


  (cond ((let ((end (+ pos (length close-delim))))
           (and (<= end (point-max))
                (string= (buffer-substring-no-properties pos end)
                         close-delim)))
         (goto-char xmltok-start))
        ((progn
           (goto-char pos)
           (forward-line -1)
+          (while (looking-at "^[[:blank:]]*$")
+            (forward-line -1))
           (<= (point) xmltok-start))
         (goto-char (+ xmltok-start (length open-delim)))
         (when (and (string= open-delim "<!--")
                    (looking-at " "))
           (goto-char (1+ (point)))))
        (t (back-to-indentation)))
  (current-column))


For test cases, create foo.xml containing:

<foo>
  <!--
      bar

foo
  -->
</foo>

An indent (TAB key) on the "foo" line should align it with the bar.

For test cases, create two versions of foo.xml, the first where there is a completely empty line between the bar and foo lines. The other version of foo.xml should have the line between bar and foo containing a few spaces.

Thanks
John


________________________________
From: John Ciolfi <ciolfi <at> mathworks.com>
Sent: Wednesday, October 2, 2024 7:59 AM
To: Stefan Kangas <stefankangas <at> gmail.com>; Eli Zaretskii <eliz <at> gnu.org>
Cc: rpluim <at> gmail.com <rpluim <at> gmail.com>; 73206 <at> debbugs.gnu.org <73206 <at> debbugs.gnu.org>
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent correctly, nxml-mode.el

Hi

Using "^$" or "^[[:blank:]]*$" is fine. The difference is very minor. Consider foo.xml where the visibly "empty" line contains a single space and foo starts on the 1st column:

<foo>
  <!--
      bar

foo
  -->
</foo>

When using "^$" and you type tab on the foo line, you'll get the following where foo starts on the 2nd column:

<foo>
  <!--
      bar

 foo
  -->
</foo>

If you use "^[[:blank:]]*$, you'll get what I expected:

<foo>
  <!--
      bar

      foo
  -->
</foo>

However, if you select all and indent-region, C-M-\ on the original you'll get the expected result with either "^$" or "^[[:blank:]]*$ because nxml-mode will pad out the space line. If the "empty" line truly blank (no spaces or tabs), then the two regex's behave identical.

I suggest for test cases, two versions of foo.xml where one version of it has the empty line truly blank (no spaces or tabs) and the other version contains a space in the "empty" line.

You can use the attached nxml-mode-indent-fix.el which overrides the broken function to try things out on a stock Emacs, emacs -Q.

Thanks
John


________________________________
From: Stefan Kangas <stefankangas <at> gmail.com>
Sent: Sunday, September 29, 2024 4:47 PM
To: Eli Zaretskii <eliz <at> gnu.org>; John Ciolfi <ciolfi <at> mathworks.com>
Cc: rpluim <at> gmail.com <rpluim <at> gmail.com>; 73206 <at> debbugs.gnu.org <73206 <at> debbugs.gnu.org>
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent correctly, nxml-mode.el

Eli Zaretskii <eliz <at> gnu.org> writes:

> Stefan, does the patch with the regexp fix look correct to you?

If we want to "keep going back until we see a non-blank line", surely
the fragment should read:

    (while (looking-at "^$")
      (forward-line -1))

Since

    (looking-at "^[[:blank:]]*$")

will match both blank lines, and lines containing only blank space.

Which of the two do we want here?

I think it would also be good to add one or more tests here.

[Message part 2 (text/html, inline)]

Message #28 received at 73206-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: John Ciolfi <ciolfi <at> mathworks.com>
Cc: rpluim <at> gmail.com, 73206-done <at> debbugs.gnu.org, stefankangas <at> gmail.com
Subject: Re: bug#73206: 28.2; xml comment with blank lines to do not indent
 correctly, nxml-mode.el
Date: Sat, 10 May 2025 13:12:53 +0300

> From: John Ciolfi <ciolfi <at> mathworks.com>
> CC: "rpluim <at> gmail.com" <rpluim <at> gmail.com>, "73206 <at> debbugs.gnu.org"
> 	<73206 <at> debbugs.gnu.org>
> Date: Wed, 30 Apr 2025 10:55:07 +0000
> 
> I see this bug isn't fixed in Emacs 30. Is it possible to fix? The right solution is to update
> nxml-compute-indent-in-delimited-token to contain "(while (looking-at "^[[:blank:]]*$") (forward-line -1))" to
> obtain the correct indentation level for text in xml comments when there's blank lines.

Thanks, I've now installed this on the emacs-30 branch, and I'm
closing this bug.

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