Support IEditorAssociationOverride

[ghentschke]

We are currently working on a new LSP based C/C++ Editor.
Currently I'am working on this issue

The file association for C/C++ source or header file to an editor should be dependent on the project settings. Therefor the user can select to prefer the new LSP based editor for his project.

The current implementation to override the default association of an editor to a file is based on this extension point: org.eclipse.ui.ide.editorAssociationOverride

The problem is that the cdt method org.eclipse.cdt.internal.ui.util.EditorUtility.getEditorID(IEditorInput, Object) does not care about the overriden default editor by the implementation of org.eclipse.ui.ide.editorAssociationOverride.

The fix are 5 lines of code in org.eclipse.cdt.internal.ui.util.EditorUtility.getEditorID(IEditorInput, Object):

The charm of this solution is, that the default C/C++ editor can be overriden by the org.eclipse.ui.ide.editorAssociationOverride extension point.

[jonahgraham]

This looks good to me (but may need a null check on return of getEditorDescriptor?). Can you provide a PR so we can proceed?

[ghentschke]

I'll provide a pull request. Null check should not be necessary. The method getEditorDescrioptor will throw a PartInitException if no valid editor can be found.

[jonahgraham]

Fixed by #345