bug#65678: 30.0.50; EWW rendered errs when the EWW buffer is closed before the page gets loaded

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@posteo.net>
> Date: Fri, 01 Sep 2023 13:44:26 +0000
> 
> When I quickly open and close a EWW page, I get the following error
> after a while:
> 
> Debugger entered--Lisp error: (error "Selecting deleted buffer")
>   (eww-render (:peer ...) 
> "https://sfba.social/@kickingvegas/1109829258114145..."; nil #<killed buffer> 
> nil)
>   (url-http-activate-callback)
>   (url-http-chunked-encoding-after-change-function 12257 12929 672)
>   (url-http-generic-filter #<process sfba.social> 
> "\312V\5.-i\205KKZ\341R\236o;%.-\326/p)\357\317\0G\342Rx\33B\215(q\247b\277\200\245$G\337\360\306\335\352\364\5,-...")
> 
> I'd expect no error to be thrown and the rendered silently stopping.

I couldn't easily simulate that here (you didn't say what you do to
"close a EWW page"), so would you please see if the change below gives
good results?

diff --git a/lisp/net/eww.el b/lisp/net/eww.el
index 089e481..b87e785 100644
--- a/lisp/net/eww.el
+++ b/lisp/net/eww.el
@@ -620,47 +620,48 @@ eww-render
     (let ((redirect (plist-get status :redirect)))
       (when redirect
         (setq url redirect)))
-    (with-current-buffer buffer
-      ;; Save the https peer status.
-      (plist-put eww-data :peer (plist-get status :peer))
-      ;; Make buffer listings more informative.
-      (setq list-buffers-directory url)
-      ;; Let the URL library have a handle to the current URL for
-      ;; referer purposes.
-      (setq url-current-lastloc (url-generic-parse-url url)))
-    (unwind-protect
-       (progn
-         (cond
-           ((and eww-use-external-browser-for-content-type
-                 (string-match-p eww-use-external-browser-for-content-type
-                                 (car content-type)))
-            (erase-buffer)
-            (insert "<title>Unsupported content type</title>")
-            (insert (format "<h1>Content-type %s is unsupported</h1>"
-                            (car content-type)))
-            (insert (format "<a href=%S>Direct link to the document</a>"
-                            url))
-            (goto-char (point-min))
-           (eww-display-html charset url nil point buffer encode))
-          ((eww-html-p (car content-type))
-           (eww-display-html charset url nil point buffer encode))
-          ((equal (car content-type) "application/pdf")
-           (eww-display-pdf))
-          ((string-match-p "\\`image/" (car content-type))
-           (eww-display-image buffer))
-          (t
-           (eww-display-raw buffer (or encode charset 'utf-8))))
-         (with-current-buffer buffer
-           (plist-put eww-data :url url)
-           (eww--after-page-change)
-           (setq eww-history-position 0)
-           (and last-coding-system-used
-                (set-buffer-file-coding-system last-coding-system-used))
-           (run-hooks 'eww-after-render-hook)
-            ;; Enable undo again so that undo works in text input
-            ;; boxes.
-            (setq buffer-undo-list nil)))
-      (kill-buffer data-buffer))))
+    (when (buffer-live-p buffer)
+      (with-current-buffer buffer
+        ;; Save the https peer status.
+        (plist-put eww-data :peer (plist-get status :peer))
+        ;; Make buffer listings more informative.
+        (setq list-buffers-directory url)
+        ;; Let the URL library have a handle to the current URL for
+        ;; referer purposes.
+        (setq url-current-lastloc (url-generic-parse-url url)))
+      (unwind-protect
+         (progn
+           (cond
+             ((and eww-use-external-browser-for-content-type
+                   (string-match-p eww-use-external-browser-for-content-type
+                                   (car content-type)))
+              (erase-buffer)
+              (insert "<title>Unsupported content type</title>")
+              (insert (format "<h1>Content-type %s is unsupported</h1>"
+                              (car content-type)))
+              (insert (format "<a href=%S>Direct link to the document</a>"
+                              url))
+              (goto-char (point-min))
+             (eww-display-html charset url nil point buffer encode))
+            ((eww-html-p (car content-type))
+             (eww-display-html charset url nil point buffer encode))
+            ((equal (car content-type) "application/pdf")
+             (eww-display-pdf))
+            ((string-match-p "\\`image/" (car content-type))
+             (eww-display-image buffer))
+            (t
+             (eww-display-raw buffer (or encode charset 'utf-8))))
+           (with-current-buffer buffer
+             (plist-put eww-data :url url)
+             (eww--after-page-change)
+             (setq eww-history-position 0)
+             (and last-coding-system-used
+                  (set-buffer-file-coding-system last-coding-system-used))
+             (run-hooks 'eww-after-render-hook)
+              ;; Enable undo again so that undo works in text input
+              ;; boxes.
+              (setq buffer-undo-list nil)))
+        (kill-buffer data-buffer)))))
 
 (defun eww-parse-headers ()
   (let ((headers nil))