bug#68336: 29.1.90; eww: error when eww-retrieve-command is set to 'sync

[Phil Sainty]

Customize `eww-retrieve-command' to `sync' -- the customize label
is "Use `url-retrieve-synchronously'" -- or simply:

 (setq eww-retrieve-command 'sync)

Now any `eww' invocation fails with:

apply: Wrong type argument: stringp, nil

I see the error in my builds of 29 and 30, but not in 28.2.

My 30.0.50 build dated back to 2023-09-21, so I've just
compiled a fresh build of 30 and no longer see the *error*,
but it still doesn't work -- the page is never rendered.

Example in Emacs 29:

 (setq eww-retrieve-command 'sync)
 (eww "http://example.com";)

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  eww-render(nil "http://example.com/"; "http://example.com/"; nil 
#<buffer *eww*>)
  apply(eww-render nil "http://example.com/"; ("http://example.com/"; nil 
#<buffer *eww*>))
  eww-retrieve("http://example.com/"; eww-render ("http://example.com/"; 
nil #<buffer *eww*>))
  eww("http://example.com";)

Or after loading the uncompiled eww.el:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  set-buffer(nil)
  (save-current-buffer (set-buffer buffer) (plist-put eww-data :peer 
(plist-get status :peer)) (setq list-buffers-directory url) (setq 
url-current-lastloc (url-generic-parse-url url)))
  ...
  eww-render(nil "http://example.com/"; "http://example.com/"; nil 
#<buffer *eww*>)

That BUFFER arg to `set-buffer' looks like it's nil on account
of an additional duplicate argument passed to `eww-render':

  eww-render(nil "http://example.com/"; "http://example.com/"; nil 
#<buffer *eww*>)

should have been:

  eww-render(nil "http://example.com/"; nil #<buffer *eww*>)

So I think the bug is the last line here:

 (defun eww-retrieve (url callback cbargs)
   (cond
    ((null eww-retrieve-command)
     (url-retrieve url #'eww-render cbargs))
    ((eq eww-retrieve-command 'sync)
     (let ((data-buffer (url-retrieve-synchronously url)))
       (with-current-buffer data-buffer
         (apply #'eww-render nil url cbargs))))

Where cbargs evidentially contains the URL already, so it
should presumably be:

 (apply #'eww-render nil cbargs)

I can confirm that this change fixes my example case (but I haven't
tried to find out if the situation is more complicated than that).


-Phil




In GNU Emacs 29.1.90 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0, Xaw scroll bars) of 2023-10-24 built on phil-lp
Repository revision: cc3e436c822343f72f3ede6b638e1b68cd434583
Repository branch: HEAD
Windowing system distributor 'The X.Org Foundation', version 
11.0.12101004
System Description: Ubuntu 22.04.3 LTS

Configured using:
 'configure --prefix=/home/phil/emacs/29.x.nc/usr/local
 --with-native-compilation=aot --with-x-toolkit=lucid --without-sound
 '--program-transform-name=s/^ctags$/ctags_emacs/''

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBSELINUX LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG
RSVG SECCOMP SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP
X11 XDBE XIM XPM LUCID ZLIB

Important settings:
  value of $LC_MONETARY: en_NZ.UTF-8
  value of $LC_NUMERIC: en_NZ.UTF-8
  value of $LC_TIME: en_NZ.UTF-8
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Dired by name

Minor modes in effect:
  savehist-mode: t
  windmove-mode: t
  winner-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny rfc822
mml mml-sec password-cache epa derived epg rfc6068 epg-config gnus-util
text-property-search time-date mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils comp comp-cstr warnings icons
subr-x rx cl-seq cl-macs gv cl-extra help-mode bytecomp byte-compile
savehist windmove winner ring dired-aux cl-loaddefs cl-lib dired
dired-loaddefs advice rmc iso-transl tooltip cconv eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel
term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo x-toolkit
x multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 84935 7813)
 (symbols 48 7538 0)
 (strings 32 22145 2035)
 (string-bytes 1 667777)
 (vectors 16 16684)
 (vector-slots 8 344081 16889)
 (floats 8 35 41)
 (intervals 56 440 0)
 (buffers 984 14))