PDE should not warn if resource URI of unknown scheme cannot be found #2031
Description
This is a restart of issue https://bugs.eclipse.org/bugs/show_bug.cgi?id=527741 in nowadays Eclipse bugtracking facility.
The Eclipse Plugin Development Editor has a very nice validation feature for resource locations denoted in plugin.xml: If the corresponding resource cannot be found (Typically caused by a typo of the user, for example), the xml element is marked with a warning that clearly indicates the problem:
This is an excellent approach for resource URIs that are understood by the PDE, but very unfortunate when programmers have registered an org.osgi.service.url.URLStreamHandlerService OSGi service that specifies a user-defined URI scheme (protocol), which is of-course unknown to the PDE. Since years we use successfully in our company a plugin extension that allows to register image resource locations for a concrete ID value via a user-defined URI scheme (e.g. "image-id"). The advantage is that these IDs are stable, although the referenced icon location can be configured differently. The only disadvantage of that concept is that our plugin.xml's are now full of warnings, because the PDE resource validation doesn't understand the URI scheme and chokes for each referenced image-id URI.
The following two Eclipse projects demonstrate the problem.
In this case the warnings are just annoying:
In the bugzilla issue's comment 6 there was encouragement to adjust the current behaviour so, that in case of an syntactically valid URI that does have a scheme different from "file" or "platform", we should ignore an unknown scheme.