[Orgmode] Bug: org-make-link-string incorrect with URL containing escapes [6.34a]

[Geert Kloosterman]

Emacs  : GNU Emacs 23.1.1 (i386-redhat-linux-gnu, GTK+ Version 2.18.3)
 of 2009-12-02 on x86-7.fedora.phx.redhat.com
Package: Org-mode version 6.34a

Hi all,

When an org link is created from an URL containing a hex escape
`org-make-link-string' creates a link that ends up corrupted the moment
it is followed (e.g. using `org-open-at-point').

I've traced this back to `org-link-escape' and `org-link-unescape'.  The
following shows how the hex code "%2B" is converted to a "+" after an
escaping round trip:

    (org-link-unescape (org-link-escape 
"http://some.host.com/form?&id=blah%2Bblah";))
    ==> 
    "http://some.host.com/form?&id=blah+blah";

In my case this small change ended up in a broken URL.

Additionally, when the URL-escape happens to be in lower case (or
otherwise not present in `org-link-escape-chars') we end up with an
error:

    (org-link-unescape (org-link-escape 
"http://some.host.com/form?&id=blah%2bblah";))
    ==> 
    Debugger entered--Lisp error: (wrong-type-argument characterp nil)
      char-to-string(nil)
      ...

When `org-url-encoding-use-url-hexify' is set to `t' we do get a proper
round trip of the URL containing hex-escapes:

    (setq org-url-encoding-use-url-hexify t)
    (org-link-unescape (org-link-escape 
"http://some.host.com/form?&id=blah%2bblah";))
    ==>
    "http://some.host.com/form?&id=blah%2bblah";


Setting `org-url-encoding-use-url-hexify' does not fix the complete
problem however: `org-open-at-point' still did not end up with the
proper URL.   Within `org-open-at-point' there is another call to
`org-link-escape':

    (org-link-escape path org-link-escape-chars-browser)

This time a mapping table is passed in explicitly (the second argument).
However, when `org-url-encoding-use-url-hexify' is set,a this mapping
table isn't used, resulting (again) in a broken URL.

I have attached a patch that fixes the problem: do not use url-hexify in
`org-link-escape' and `org-link-unescape' when an explicit mapping table
has been specified.  

In summary:
 - the default behaviour of `org-link-escape', with
   `org-url-encoding-use-url-hexify' set to nil, has some issues with
   handling URLS which contain url-encoded hex escapes
 - when a mapping table is passed to `org-link-escape' and
   `org-link-unescape', they should probably not use url-hexify.
   Patch attached. 

Best regards,
Geert Kloosterman

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