> Making the change in mm-url.el sounds scary: that code was written
> many years ago, and who knows where it is used?
Yeah, that makes sense. I'll see what I can find about that, at least
within emacs itself.
> The reason for testing bolp there is not explained, but I'm guessing
> they didn't want to craete an empty line?
Not sure. It looks like it was introduced during a patch intended to fix
submitting binary data. Would it make sense to CC the two authors of the
following commits?
I dug into the history a bit to try to find out where =(unless (bolp)=
came from
#+begin_src bash
git log -L '/(unless (bolp)/,+1:lisp/gnus/mm-url.el' > unless-bolp
#+end_src
It looks like it was introduced in this commit
#+begin_quote
commit fca2f70380dcb054497470aaf8eda6173063928e
Author: Kenjiro Nakayama <
nakayamakenjiro@gmail.com>
Date: Mon Nov 10 22:33:55 2014 +0100
Allow uploading files from eww
#+end_quote
and the "\r\n" was included unconditionally before the boundary
#+begin_src elisp
;; use the boundary as a separator
(concat "\r\n--" boundary "\r\n")
#+end_src
Then it this commit changed it
#+begin_quote
commit a6e0188dffc394698d9ffbef50401f14a31c8722
Author: Lars Ingebrigtsen <
larsi@gnus.org>
Date: Thu Oct 13 21:39:29 2016 +0200
Fix problem with submitting binary data via HTTP forms
#+end_quote
to the following
#+begin_src elisp
(unless (bolp)
(insert "\r\n"))
#+end_src
plus a bunch of "\r\n"s scattered throughout the different conditions.
It's not clear to me how the behavior of the function changed.
It looks like maybe instead of the initial diff I proposed, something
like this would produce more accurate output for file uploads, and also
change the surrounding code as little as possible,
#+begin_quote
diff --git a/lisp/gnus/mm-url.el b/lisp/gnus/mm-url.el
index 11847a79f17..686dea20b6a 100644
--- a/lisp/gnus/mm-url.el
+++ b/lisp/gnus/mm-url.el
@@ -430,7 +430,8 @@ mm-url-encode-multipart-form-data
(insert filedata))
;; How can this possibly be useful?
((integerp filedata)
- (insert (number-to-string filedata))))))
+ (insert (number-to-string filedata)))))
+ (insert "\r\n"))
((equal name "submit")
(insert
"Content-Disposition: form-data; name=\"submit\"\r\n\r\nSubmit\r\n"))
#+end_quote
But it seems like it would be better to do a larger rewrite that
consolidates the places where "\r\n" is added before the non-initial
boundary.
In order to figure that out, I will read the two versions more closely
to figure out what the differences are and write some ERT tests showing
the difference. Hopefully that will clear things up.