bug#34387: 26.1; Gnus: handle empty message parts

bug#34387: 26.1; Gnus: handle empty message parts

[Christophe Troestler]

Hi,

Some messages only contain an attachment (no body) and (gnus-article-prepare-display) choke on the empty part.  More specifically, `gnus-mime-display-single' does (narrow-to-region beg (point)) which fails if the part is empty.  An easy fix is to write

      (when (< beg (point))
        (narrow-to-region beg (point))
        (if (eq handle gnus-article-mime-handles)
          ...))



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bug#34387: Acknowledgement (26.1; Gnus: handle empty message parts)

[Christophe Troestler]

For those who encounter this problem, a fix that does not require to modify the body of the function gnus-mime-display-single is:

(define-advice gnus-mime-display-single (:around (oldfn &rest handle) fix)
  "Protect against bad handling of empty message parts."
  (ignore-errors (apply oldfn handle)))

bug#34387: 26.1; Gnus: handle empty message parts

[Katsumi Yamaoka]

On Fri, 08 Feb 2019 15:58:19 +0100, Christophe Troestler wrote:
> Some messages only contain an attachment (no body) and
> (gnus-article-prepare-display) choke on the empty part.
> More specifically, `gnus-mime-display-single' does
> (narrow-to-region beg (point)) which fails if the part is empty.

Could you let me know how it fails?  Otherwise, could you show
me a sample email in question?  Unfortunately I'm not successful
in making such an email that causes the problem so far, and trying
(narrow-to-region beg beg) and (narrow-to-region (point) (point))
cause nothing special.

But I found at least two other kinds of problems in relation to
an empty attachment:

1. In the article buffer, pressing the RET key on an empty
 text/plain attachment conceals the succeeding other attachments,
 does not toggle.  `g' restores them of course, though.

2. Some kind of an empty mail isn't able to be edited using the
 `e' command (gnus-summary-edit-article), that is, a single part
 email whose body is an empty attachment.  Gnus misunderstands
 that the header is its body.

On Fri, 08 Feb 2019 16:39:47 +0100, Christophe Troestler wrote:
> For those who encounter this problem, a fix that does not require to
> modify the body of the function gnus-mime-display-single is:

> (define-advice gnus-mime-display-single (:around (oldfn &rest handle) fix)
>   "Protect against bad handling of empty message parts."
>   (ignore-errors (apply oldfn handle)))

I'd like to fix those problems in the Gnus code. :)

Thanks.
Regards,

bug#34387: 26.1; Gnus: handle empty message parts

[Christophe Troestler]

[-- Attachment #1: Type: text/plain, Size: 4448 bytes --]


On 12 February 2019 at 05:34 CET, Katsumi Yamaoka wrote:
>
> […] Could you let me know how it fails?

Here is the debugger trace (message attached) :

Debugger entered--Lisp error: (args-out-of-range 4409 4410)
  #f(compiled-function (handle) #<bytecode 0x1471e8d>)((#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil))
  apply(#f(compiled-function (handle) #<bytecode 0x1471e8d>) (#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil))
  gnus-mime-display-single@fix(#f(compiled-function (handle) #<bytecode 0x1471e8d>) (#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil))
  apply(gnus-mime-display-single@fix #f(compiled-function (handle) #<bytecode 0x1471e8d>) (#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil))
  gnus-mime-display-single((#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil))
  gnus-mime-display-part((#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil))
  mapcar(gnus-mime-display-part ((#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil) (#<buffer  *mm*-589619> ("application/pdf" (name . "homologie_de_contact_legendrienne_bilinearisee.pdf")) base64 nil ("attachment" (modification-date . "Fri, 08 Feb 2019 11:42:34 GMT") (creation-date . "Fri, 08 Feb 2019 11:40:17 GMT") (size . "308005") (filename . "homologie_de_contact_legendrienne_bilinearisee.pdf")) "homologie_de_contact_legendrienne_bilinearisee.pdf" nil nil)))
  gnus-mime-display-mixed(((#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil) (#<buffer  *mm*-589619> ("application/pdf" (name . "homologie_de_contact_legendrienne_bilinearisee.pdf")) base64 nil ("attachment" (modification-date . "Fri, 08 Feb 2019 11:42:34 GMT") (creation-date . "Fri, 08 Feb 2019 11:40:17 GMT") (size . "308005") (filename . "homologie_de_contact_legendrienne_bilinearisee.pdf")) "homologie_de_contact_legendrienne_bilinearisee.pdf" nil nil)))
  gnus-mime-display-part((#("multipart/mixed" 0 15 (boundary "_002_VI1PR0101MB215751953182701525CB4AD9E7690VI1PR0101MB2157_" buffer #<buffer  *mm*-468382> from "Damien.GALANT@student.umons.ac.be" start nil)) (#<buffer  *mm*-671873> ("text/html" (charset . "Windows-1252")) quoted-printable (lambda nil (let ((inhibit-read-only t)) (delete-region #<marker at 4408 in *Article*> #<marker at 4408 in *Article*>))) nil nil nil nil) (#<buffer  *mm*-589619> ("application/pdf" (name . "homologie_de_contact_legendrienne_bilinearisee.pdf")) base64 nil ("attachment" (modification-date . "Fri, 08 Feb 2019 11:42:34 GMT") (creation-date . "Fri, 08 Feb 2019 11:40:17 GMT") (size . "308005") (filename . "homologie_de_contact_legendrienne_bilinearisee.pdf")) "homologie_de_contact_legendrienne_bilinearisee.pdf" nil nil)))
  gnus-display-mime()
  gnus-article-prepare-display()

> Otherwise, could you show me a sample email in question? […]

Attached.

>> […] (define-advice gnus-mime-display-single (:around (oldfn &rest handle) fix)
>>   "Protect against bad handling of empty message parts."
>>   (ignore-errors (apply oldfn handle)))
>
> I'd like to fix those problems in the Gnus code. :)

Sure — it was just a suggestion in the meantime! ;-)

Best,
Christophe


[-- Attachment #2: Plan th�orie des nSuds --]
[-- Type: message/rfc822, Size: 421186 bytes --]

[-- Attachment #2.1.1: Type: text/html, Size: 416 bytes --]

[-- Attachment #2.1.2: homologie_de_contact_legendrienne_bilinearisee.pdf --]
[-- Type: application/pdf, Size: 307661 bytes --]

bug#34387: 26.1; Gnus: handle empty message parts

[Katsumi Yamaoka]

On Tue, 12 Feb 2019 08:31:39 +0100, Christophe Troestler wrote:
> Here is the debugger trace (message attached) :

> Debugger entered--Lisp error: (args-out-of-range 4409 4410)
>   #f(compiled-function...)(PART1)
>   apply(#f(compiled-function...) PART1)
>   gnus-mime-display-single@fix(#f(compiled-function...) PART1)
>   apply(gnus-mime-display-single@fix #f(compiled-function...) PART1)
>   gnus-mime-display-single(PART1)
>   gnus-mime-display-part(PART1)
>   mapcar(gnus-mime-display-part (PART1 PART2))
>   gnus-mime-display-mixed((PART1 PART2))
>   gnus-mime-display-part((...PART1 PART2))
>   gnus-display-mime()
>   gnus-article-prepare-display()

;; Where PART1 is the html part and PART2 is the pdf part.

If it is (narrow-to-region beg (point)) in gnus-mime-display-single
to issue (args-out-of-range 4409 4410), I guess an html rendering
function deletes buffer's contents so that the buffer's end point
may be 4409.  Here is a model to reproduce the same error:

(with-temp-buffer               ;; article buffer
  (insert-char ?x 4409)
  (let ((beg (point)))          ;; buffer's end point == 4410
    (delete-char -1)            ;; html function does this
    (narrow-to-region beg (point))))
 => (args-out-of-range 4409 4410)

The default html function is mm-shr, that gnus-mime-display-single
calls by way of mm-display-part, mm-display-inline, and
mm-inline-text-html.  At that time, the point is positioned at
the end of the article buffer, where the header lines and a
single empty line are there.

>> Otherwise, could you show me a sample email in question? […]
> Attached.

Thanks.  However, I couldn't reproduce the error with the mail
that I copied to my nnml group.  I tried it using Emacs 26.1
with no ~/.emacs, no ~/.gnus.el, but ~/.newsrc.eld,
(setq gnus-select-method '(nnnil)), and every candidate for
mm-text-html-renderer.  The only thing that reproduces it is:

(defadvice mm-shr (before delete-ceiling-newlines activate)
  "Delete newlines before the point."
  (skip-chars-backward "\n")
  (delete-region (point) (point-max)))

Well, if you have time for analyzing the problem, don't you try
edebug on the functions listed above?

Regards,

;; I'm going to fix the other 2 issues anyway.

bug#34387: 26.1; Gnus: handle empty message parts

[Christophe Troestler]

On 13 February 2019 at 05:53 CET, Katsumi Yamaoka wrote:
>
> […] If it is (narrow-to-region beg (point)) in gnus-mime-display-single to issue (args-out-of-range 4409 4410), I guess an html rendering function deletes buffer's contents so that the buffer's end point may be 4409.  Here is a model to reproduce the same error:
>
> (with-temp-buffer               ;; article buffer
>   (insert-char ?x 4409)
>   (let ((beg (point)))          ;; buffer's end point == 4410
>     (delete-char -1)            ;; html function does this
>     (narrow-to-region beg (point))))
>  => (args-out-of-range 4409 4410)
>
> The default html function is mm-shr, that gnus-mime-display-single calls by way of mm-display-part, mm-display-inline, and mm-inline-text-html.  At that time, the point is positioned at the end of the article buffer, where the header lines and a single empty line are there.

Thanks for your analysis.  I indeed had an advice executed after mm-shr to remove trailing whitespace—these making sometimes the rendered text hard to read.  Deleting the advice makes the call work.

What approach would you recommend to remove trailing whitespace after rendering HTML?

Best,
C.

bug#34387: 26.1; Gnus: handle empty message parts

[Katsumi Yamaoka]

On Wed, 13 Feb 2019 18:26:44 +0100, Christophe Troestler wrote:
> Thanks for your analysis.  I indeed had an advice executed after
> mm-shr to remove trailing whitespace—these making sometimes the
> rendered text hard to read.  Deleting the advice makes the call
> work.

Bingo! :)

> What approach would you recommend to remove trailing whitespace
> after rendering HTML?

The point would be to delete only whitespace that mm-shr inserts.
How about this?

(defadvice mm-shr (around delete-leading-and-trailing-whitespace activate)
  "Delete leading and trailing whitespace in Gnus article buffer."
  (when (derived-mode-p 'gnus-article-mode)
    (save-restriction
      (narrow-to-region (point) (point))
      ad-do-it
      (goto-char (point-min))
      (skip-chars-forward "\t\n ")
      (delete-region (point-min) (point))
      (goto-char (point-max))
      (skip-chars-backward "\t\n ")
      (delete-region (point) (point-max))
      (insert "\n"))))

I'll close this thread after fixing the other two related bugs.

> 1. In the article buffer, pressing the RET key on an empty
>  text/plain attachment conceals the succeeding other attachments,
>  does not toggle.  `g' restores them of course, though.

> 2. Some kind of an empty mail isn't able to be edited using the
>  `e' command (gnus-summary-edit-article), that is, a single part
>  email whose body is an empty attachment.  Gnus misunderstands
>  that the header is its body.

Regards,

bug#34387: 26.1; Gnus: handle empty message parts

[Katsumi Yamaoka]

On Thu, 14 Feb 2019 08:20:20 +0900, Katsumi Yamaoka wrote:
> I'll close this thread after fixing the other two related bugs.

>> 1. In the article buffer, pressing the RET key on an empty
>>  text/plain attachment conceals the succeeding other attachments,
>>  does not toggle.  `g' restores them of course, though.

>> 2. Some kind of an empty mail isn't able to be edited using the
>>  `e' command (gnus-summary-edit-article), that is, a single part
>>  email whose body is an empty attachment.  Gnus misunderstands
>>  that the header is its body.

Done.  Closing.

bug#34387: 26.1; Gnus: handle empty message parts

[Christophe Troestler]

[-- Attachment #1: Type: text/plain, Size: 1375 bytes --]


On 14 February 2019 at 00:20 CET, Katsumi Yamaoka wrote:
>
> The point would be to delete only whitespace that mm-shr inserts.
> How about this?
>
> (defadvice mm-shr (around delete-leading-and-trailing-whitespace activate)
>   "Delete leading and trailing whitespace in Gnus article buffer."
>   (when (derived-mode-p 'gnus-article-mode)
>     (save-restriction
>       (narrow-to-region (point) (point))
>       ad-do-it
>       (goto-char (point-min))
>       (skip-chars-forward "\t\n ")
>       (delete-region (point-min) (point))
>       (goto-char (point-max))
>       (skip-chars-backward "\t\n ")
>       (delete-region (point) (point-max))
>       (insert "\n"))))

The point is to delete all trailing whitespace coming from the conversion of HTML to text.  Without this, some emails (such as the one attached) are hard to read because the lines end with so many whitespaces that they take several lines on the screen (filled with spaces).  The following does what I want (and does not trigger the bug, thanks to the narrowing).

(define-advice mm-shr (:around (oldfn &rest handle) delete-trailing-whitespace)
  "Delete leading and trailing whitespace in Gnus article buffer."
  (when (derived-mode-p 'gnus-article-mode)
    (save-restriction
      (narrow-to-region (point) (point))
      (apply oldfn handle)
      (delete-trailing-whitespace))))

Thanks,
C.




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bug#34387: 26.1; Gnus: handle empty message parts

[Katsumi Yamaoka]

On Thu, 14 Feb 2019 13:30:34 +0100, Christophe Troestler wrote:
> The point is to delete all trailing whitespace coming from the
> conversion of HTML to text.  Without this, some emails (such as the
> one attached) are hard to read because the lines end with so many
> whitespaces that they take several lines on the screen (filled with
> spaces).  The following does what I want (and does not trigger the
> bug, thanks to the narrowing).

> (define-advice mm-shr (:around (oldfn &rest handle) delete-trailing-whitespace)
>   "Delete leading and trailing whitespace in Gnus article buffer."
>   (when (derived-mode-p 'gnus-article-mode)
>     (save-restriction
>       (narrow-to-region (point) (point))
>       (apply oldfn handle)
>       (delete-trailing-whitespace))))

I see.  But, sorry, I meant to do first was:

(define-advice mm-shr (:around (oldfn &rest handle) delete-trailing-whitespace)
  "Delete leading and trailing whitespace in Gnus article buffer."
  (if (derived-mode-p 'gnus-article-mode)
      (save-restriction
	(narrow-to-region (point) (point))
	(apply oldfn handle)
	(delete-trailing-whitespace))
    (apply oldfn handle)))

That is, not to do the whitespace deletion when mm-shr is used
in other than Gnus as it might require whitespace.  Anyway the
(when ...) way makes mm-shr work only in the Gnus article buffer.
:-p

Regards,

bug#34387: 26.1; Gnus: handle empty message parts

[Christophe Troestler]

On 14 February 2019 at 23:50 CET, Katsumi Yamaoka wrote:
>
> […] I see.  But, sorry, I meant to do first was:
>
> (define-advice mm-shr (:around (oldfn &rest handle) delete-trailing-whitespace)
>   "Delete leading and trailing whitespace in Gnus article buffer."
>   (if (derived-mode-p 'gnus-article-mode)
>       (save-restriction
> 	(narrow-to-region (point) (point))
> 	(apply oldfn handle)
> 	(delete-trailing-whitespace))
>     (apply oldfn handle)))
>
> That is, not to do the whitespace deletion when mm-shr is used
> in other than Gnus as it might require whitespace.  […]

Sure.  Thanks for taking the time to attract my attention to this.

Best,
C.