w3m-url-fallback-base

[TSUCHIYA Masatoshi <tsuchiya@xxxxxxxxxx>]

>> On Tue, 18 Jul 2017 17:30:06 +0900
>> yamaoka@xxxxxxx (Katsumi Yamaoka) said as follows:

>Q1.
>========
>Why is the constant `w3m-url-fallback-base' "http:///", not
>"http://"?  The function `w3m-expand-url' uses it and behaves as
>follows:

>(w3m-expand-url "www.gnu.org") => "http:///www.gnu.org"

>It is invalid.  Shouldn't the result be "http://www.gnu.org"?
>--------
>なぜ定数 `w3m-url-fallback-base' は、"http://" ではなくて
>"http:///" なのですか?  (w3m-expand-url "www.gnu.org") は
>"http:///www.gnu.org" を返しますが、無効な値です。その結果は
>"http://www.gnu.org" になるべきではないですか?

Well, I checked the revision when `w3m-url-fallback-base' was
introduced.  It was w3m.el revision 1.416.  And the change is attached
at the end of this message.

I also checked the archive of our ancient mailing list.  I think this
change was introduced as the result of the discussion around
"[emacs-w3m:01656] w3m-expand-url".

And then, I reread the discussion and the code, finally, I think that
this default value has no technical ground.  My suppose grounds to this
code:

      (setq base (or w3m-current-base-url
		     w3m-current-url
		     w3m-url-fallback-base)))

This code means that `w3m-url-fallback-base' is simply used only when no
appropriate default value is given.

In other words, if the context gives another appropriate default value,
the context sholud set the default value to `w3m-current-base-url' or
`w3m-url-fallback-base', in my opinion.

-- 
TSUCHIYA Masatoshi

RCS file: /storage/cvsroot/emacs-w3m/w3m.el,v
retrieving revision 1.415
retrieving revision 1.416
diff -u -u -r1.415 -r1.416
--- w3m.el	10 Oct 2001 02:42:03 -0000	1.415
+++ w3m.el	10 Oct 2001 04:22:48 -0000	1.416
@@ -127,7 +127,7 @@
 
 (defconst emacs-w3m-version
   (eval-when-compile
-    (let ((rev "$Revision: 1.415 $"))
+    (let ((rev "$Revision: 1.416 $"))
       (and (string-match "\\.\\([0-9]+\\) \$$" rev)
 	   (format "1.1.%d"
 		   (- (string-to-number (match-string 1 rev)) 233)))))
@@ -1613,10 +1613,13 @@
 					   'help-echo help
 					   'balloon-help balloon))))
 	 (name
-	  (when (re-search-forward "<\\|\n" nil t)
-	    (setq end (match-beginning 0))
+	  (when (re-search-forward "[<\n]" nil t)
+	    (goto-char (setq end (match-beginning 0)))
 	    (when (= start end)
-	      (setq end (min (1+ end) (point-max))))
+	      (setq end (min (if (looking-at "\\(<[^>]*>\\)+")
+				 (1+ (match-end 0))
+			       (1+ end))
+			     (point-max))))
 	    (w3m-add-text-properties start end
 				     (list 'w3m-name-anchor name)))))))
     (when w3m-next-url
@@ -2999,11 +3002,20 @@
 refered in `w3m-expand-url' to keep backward compatibility which is
 described in Section 5.2 of RFC 2396.")
 
+(defconst w3m-url-fallback-base "http:///")
+
 (defun w3m-expand-url (url &optional base)
   "Convert URL to absolute, and canonicalize it."
   (save-match-data
-    (unless base
-      (setq base (or w3m-current-base-url w3m-current-url "")))
+    (if base
+	(unless (and (string-match w3m-url-components-regexp base)
+		     (match-beginning 1)
+		     (match-beginning 3))
+	  (error "BASE must have a scheme part and a net-location part: %s"
+		 base))
+      (setq base (or w3m-current-base-url
+		     w3m-current-url
+		     w3m-url-fallback-base)))
     (string-match w3m-url-components-regexp url)
     ;; Remove an empty query part and an empty fragment part.
     (or (and (match-beginning 6)
@@ -3023,7 +3035,7 @@
 	(let ((scheme (match-string 2 url)))
 	  (if (and (member scheme w3m-url-hierarchical-schemes)
 		   (string-match w3m-url-components-regexp base)
-		   (string= scheme (match-string 2 base)))
+		   (equal scheme (match-string 2 base)))
 	      (w3m-expand-url (substring url (match-end 1)) base)
 	    url))))
      ((match-beginning 3)