bug#36520: Form submition in eww doesn't work if file field is left empty

bug#36520: Form submition in eww doesn't work if file field is left empty

[Ivaylo Ilionov]

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When submitting form with various fields including one optional
field for file upload, if the file filed is left empty - the
submition doesn't work.

The error is: Wrong type argument: stringp, nil

I've tracked the problem to the function 'eww-submit' which tries
to open a file for upload (the file was never initialized by the
html form).

My fix is to check if the property is set in the file "eww.el.gz" after
line 1435:

> ((equal (plist-get input :type) "file")
>  ;; FIX check if property :filename is not nil
>  (when (not (null (plist-get input :filename)))
>    (push (cons "file"
>         (list (cons "filedata"
>       (with-temp-buffer
>         (insert-file-contents
>          (plist-get input :filename))
>         (buffer-string)))
>        (cons "name" (plist-get input :name))
>        (cons "filename" (plist-get input :filename))))
>   values)))

Details about my emacs:

In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 2.24.32)
 of 2019-07-05 built on debian
Repository revision: f24d47359d9b6621215f20795d585c5024d91783
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)


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bug#36520: Form submition in eww doesn't work if file field is left empty

[Basil L. Contovounesios]

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tags 36520 + patch
quit

Ivaylo Ilionov <ivaylo.ilionov@outlook.com> writes:

> When submitting form with various fields including one optional
> field for file upload, if the file filed is left empty - the
> submition doesn't work.
>
> The error is: Wrong type argument: stringp, nil

Could you please give an example of such a form, for
reproduction/testing purposes?

> I've tracked the problem to the function 'eww-submit' which tries
> to open a file for upload (the file was never initialized by the
> html form).

I wonder if the file not being initialised is a symptom of a problem
elsewhere?  An example might shed more light on this.

> My fix is to check if the property is set in the file "eww.el.gz" after
> line 1435:
>
>> ((equal (plist-get input :type) "file")
>>  ;; FIX check if property :filename is not nil
>>  (when (not (null (plist-get input :filename)))

FWIW, this is equivalent to (when (plist-get input :filename) ...).

>>    (push (cons "file"
>>         (list (cons "filedata"
>>       (with-temp-buffer
>>         (insert-file-contents
>>          (plist-get input :filename))
>>         (buffer-string)))
>>        (cons "name" (plist-get input :name))
>>        (cons "filename" (plist-get input :filename))))
>>   values)))

LGTM.  Here's a patch which achieves the same effect and additionally
cleans up this code a tiny bit:


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Fix-fileless-eww-form-submission.patch --]
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From 6c4fdcf2434391236d9ac1a891ba751e82831e37 Mon Sep 17 00:00:00 2001
From: "Basil L. Contovounesios" <contovob@tcd.ie>
Date: Sun, 7 Jul 2019 15:36:36 +0100
Subject: [PATCH] Fix fileless eww form submission

* lisp/net/eww.el (eww-submit): Ignore file inputs with no
associated file name (bug#36520).
---
 lisp/net/eww.el | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/lisp/net/eww.el b/lisp/net/eww.el
index 1125929c03..5acc645574 100644
--- a/lisp/net/eww.el
+++ b/lisp/net/eww.el
@@ -1426,15 +1426,15 @@ eww-submit
 	      (push (cons name (plist-get input :value))
 		    values)))
 	   ((equal (plist-get input :type) "file")
-	    (push (cons "file"
-			(list (cons "filedata"
-				    (with-temp-buffer
-				      (insert-file-contents
-				       (plist-get input :filename))
-				      (buffer-string)))
-			      (cons "name" (plist-get input :name))
-			      (cons "filename" (plist-get input :filename))))
-		  values))
+            (when-let ((file (plist-get input :filename)))
+              (push (list "file"
+                          (cons "filedata"
+                                (with-temp-buffer
+                                  (insert-file-contents file)
+                                  (buffer-string)))
+                          (cons "name" name)
+                          (cons "filename" file))
+                    values)))
 	   ((equal (plist-get input :type) "submit")
 	    ;; We want the values from buttons if we hit a button if
 	    ;; we hit enter on it, or if it's the first button after
-- 
2.20.1


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This is probably fine to push as-is, as it's just a defensive guard, but
I'd rather get confirmation from someone else or play around with an
example of the bug first.

Thanks,

-- 
Basil

bug#36520: Form submition in eww doesn't work if file field is left empty

[Ivaylo Ilionov]

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Basil L. Contovounesios <contovob@tcd.ie> writes:
> I wonder if the file not being initialised is a symptom of a problem
elsewhere?  An example might shed more light on this.

It's quite possible that my suggestion is a low quality patch or just
hides the real problem. I don't have a good undertanding of the
code for eww.

I've first encountered the problem in Redmine version 4.0.3.
The action which triggered the error was that for changing status
of an issue from "New" to "In Progress". The form contains
many things including the option to upload files for the issue
when changing statuses.

Here's a sample web form which demonstrates the problem:

<html> <body>
    <form action="/non-existent.cgi" method="post">
      Short comment: <input name='comment' type='text' /><br/>
      Optional file: <input name='file' type='file' /><br/>
      <input type='submit'/><br/>
      <input type='reset'/>
    </form>
</body> </html>

If a file hasn't been chosen the submition doesn't seem to work.
If a file is chosen i get a proper error from the server ("not found").

________________________________
From: Basil L. Contovounesios <contovob@tcd.ie>
Sent: Sunday, July 7, 2019 19:38
To: Ivaylo Ilionov
Cc: 36520@debbugs.gnu.org
Subject: Re: bug#36520: Form submition in eww doesn't work if file field is left empty

tags 36520 + patch
quit

Ivaylo Ilionov <ivaylo.ilionov@outlook.com> writes:

> When submitting form with various fields including one optional
> field for file upload, if the file filed is left empty - the
> submition doesn't work.
>
> The error is: Wrong type argument: stringp, nil

Could you please give an example of such a form, for
reproduction/testing purposes?

> I've tracked the problem to the function 'eww-submit' which tries
> to open a file for upload (the file was never initialized by the
> html form).

I wonder if the file not being initialised is a symptom of a problem
elsewhere?  An example might shed more light on this.

> My fix is to check if the property is set in the file "eww.el.gz" after
> line 1435:
>
>> ((equal (plist-get input :type) "file")
>>  ;; FIX check if property :filename is not nil
>>  (when (not (null (plist-get input :filename)))

FWIW, this is equivalent to (when (plist-get input :filename) ...).

>>    (push (cons "file"
>>         (list (cons "filedata"
>>       (with-temp-buffer
>>         (insert-file-contents
>>          (plist-get input :filename))
>>         (buffer-string)))
>>        (cons "name" (plist-get input :name))
>>        (cons "filename" (plist-get input :filename))))
>>   values)))

LGTM.  Here's a patch which achieves the same effect and additionally
cleans up this code a tiny bit:


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bug#36520: Form submition in eww doesn't work if file field is left empty

[Lars Ingebrigtsen]

"Basil L. Contovounesios" <contovob@tcd.ie> writes:

> This is probably fine to push as-is, as it's just a defensive guard, but
> I'd rather get confirmation from someone else or play around with an
> example of the bug first.

I did some testing, and it seemed to work fine for me, so I've applied
it to the trunk and pushed it.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no