Description Christophe Cornu 2007-06-04 10:49:16 EDT

We have exceptional cases when the action is enabled on two different files with different states but the content is identical. We only find out about that inside our SaveableCompareInput.prepareCompareInput(IProgressMonitor) implementation. In such case we return null.

SaveableCompareInput.prepareInput dereferences the input to set the title without checking if it is null. Could you set the title only if it isn't null and javadoc prepareCompareInput can return null?

The super type CompareEditorInput.prepareInput specs null is valid:

	 * If <code>null</code> is returned no differences were found and no compare editor needs to be opened.

Today we worked around it by not calling super.prepareInput

Imaging showing the history of a file and comparing any historical state with a local file. We need a server operation to decide if the contents are identical. In the common case, the compare editor shows up immediately - rapid UI feedback - and performs the fetch and comparison in the background. In some accidental cases the compare editor was not needed and the Eclipse dialog prompts the user. This seems like a good pattern.

What do you think?