I kept getting the following exception when trying to open an editor part using Eclipse RCP:
PartInitException: Unable to open editor, unknown editor ID:my.editor.id
The message was a lie -- I had registered an editor under the stipulated ID. But when I debugged into Eclipse code, I could see that my editor had not been registered. Investigating further, I found the following message in the application log:
!MESSAGE Plugin my.plugin, extension org.eclipse.ui.editors
Required attribute 'icon' not defined
It appears that the 'icon' attribute is required, even though it is not shown as such in the plug-in manifest editor. Note that the condition is reported as a 'message' and not an 'error', so if you don't go looking into the application log, you won't see it.
