Re: Using Emacs nXML mode to validate XHTML5 using the v.Nu schemas: support for HTTP-based schema URI?

[Stefan Monnier <monnier@iro.umontreal.ca>]

> - The GitHub repo hober/html5-el, which provides the datatype library 
> required by the v.Nu schemas in a Lisp-based format usable by nXML (rather 
> than, say, a Java-based library usable by Jing)

Ha!  I put something very similar into GNU ELPA's html5-schema package
a month or so ago.

>> Invalid URI: "URI `http:/// ... ' does not use the `file:' scheme"
> That's okay - it's working, which is great - but I'd prefer to point to 
> the "live" schemas via HTTP.

It might not be too hard to tweak nXML so it accepts HTTP URLs, but I'm
not sure what behavior you'd want to see exactly: the naive approach
might download all those files via HTTP every time you open an HTML
file, slowing down startup significantly.

It could also use a cache, but then it begs the question of how often to
update the cache.  So for my kind of use-case at least, I'd end up
preferring to manage the file by hand (i.e. download the files via
"git" and update them via "git pull" whenever I feel like it).

> I'd appreciate advice on adding support for HTTP URLs to that uri 
> attribute value (and also include directives in the .rnc files) or, better 
> still, an update to nXML that includes this support (I'm not a Lisp 
> programmer, but I could learn).

If you enable url-handler-mode, then Emacs will consider "http://..." as
a valid file name.  So assuming you enabled that mode, you should mostly
need to teach nXML to accept those names.  E.g. the 100% guaranteed
untested patch below might be a good start.


        Stefan


PS: I'd welcome some help to improve the html5-schema so that the HTML
    it accepts includes SVG elements.


diff --git a/lisp/nxml/rng-uri.el b/lisp/nxml/rng-uri.el
index 8fc0a01..76f9bc1 100644
--- a/lisp/nxml/rng-uri.el
+++ b/lisp/nxml/rng-uri.el
@@ -82,10 +82,11 @@ rng-uri-file-name-1
     (cond ((not scheme)
 	   (unless pattern
 	     (rng-uri-error "URI `%s' does not have a scheme" uri)))
-	  ((not (string= (downcase scheme) "file"))
-	   (rng-uri-error "URI `%s' does not use the `file:' scheme" uri)))
-    (when (not (member authority
-		       (cons (system-name) '(nil "" "localhost"))))
+	  ((not (member (downcase scheme) '("file" "http")))
+	   (rng-uri-error "URI `%s' does not use the `file:' or `http:' scheme" uri)))
+    (when (and (equal (downcase scheme) "file")
+               (not (member authority
+                            (cons (system-name) '(nil "" "localhost")))))
       (rng-uri-error "URI `%s' does not start with `file:///' or `file://localhost/'"
 	     uri))
     (when query