Description Michael Moser 2006-08-22 08:49:38 EDT

There are many places where JFace uses org.eclipse.jface.util.Assert. While I fully agree that Asserts are a fine thing if they are used to verify programming assumptions and internal consistency within a framework, they are a lousy way to check API parameters passed in! If such an assert fails a programmer gets little or no clue what is wrong and has to dig into JFace's source code to find out, why things fail. For the latter purpose please throw telling exceptions (like NullPointerException or IllegalArgumentException with some short msg.) instead of doing assertions!

Example: I just got this:
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org.eclipse.jface.util.Assert$AssertionFailedException: Assertion failed: 
	at org.eclipse.jface.util.Assert.isTrue(Assert.java:182)
	at org.eclipse.jface.util.Assert.isTrue(Assert.java:167)
	at org.eclipse.jface.viewers.AbstractTreeViewer.assertContentProviderType(AbstractTreeViewer.java:2086)
	at org.eclipse.jface.viewers.TreeViewer.assertContentProviderType(TreeViewer.java:761)
	at org.eclipse.jface.viewers.StructuredViewer.setContentProvider(StructuredViewer.java:1518)
	at org.eclipse.jface.viewers.AbstractTreeViewer.setContentProvider(AbstractTreeViewer.java:2082)
	at myplugin.AnalysisView.createViewer(AnalysisView.java:263)
...
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In my project I had just decided to change my view from a TableViewer to use a TreeViewer (formerly called a TableTreeViewer) instead and as turned out (but only by looking at the JFace source) I had forgotten to adapt the view's content provide to implement ITreeContentProvider or ITreePathContentProvider (instead of IStructuredContentProvider).

If there would be an IllegalArgumentException("content provider not implementing ITreeContentProvider nor ITreePathContentProvider") or similar the reason for the exception would have been immediately clear to me.

Michael