Error for unsupported services is confusing (bug 2025)

[Frank Warmerdam]

Folks,

Mark Zanfardino was having problems getting his WFS request to work with
MapServer, and was getting an error about "Web application error. No
template provided".  This was because he didn't have WFS server support
built into MapServer, so msOWSDispatch() never invokved the wfs dispatcher
and things fell through into the non OWS service handling code in mapserv.c.

   http://mapserver.gis.umn.edu/bugs/show_bug.cgi?id=2025

I would like to modify msOWSDispatch() to report a more specific error
message if the URL includes the string "SERVICE=" and none of the built
in dispatchers handles the request.  Something along the line of:

   "SERVICE '%s' is either not supported by MapServer, or not enabled in this 
MapServer build"

or perhaps even embed specific logic to differentiate between unrecognised
sevices, and ones which are definately not built-in but could be.

The main drawback to this is if old style URLs might have "SERVICE=...." in
them in some circumstances, as msOWSDispatch() would never let control get
past it.

I'm interested in opinions on the best approach to giving more meaningful
error messages without any undue breakage.  I'm also interested in whether
people think this change belongs in 4.10.x (I'm inclined not too back port
it).

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org