Throw an exception when trying to access an uninitialized property
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Key: TAPESTRY-1111
URL: http://issues.apache.org/jira/browse/TAPESTRY-1111
Project: Tapestry
Issue Type: Improvement
Components: Core
Affects Versions: 4.0
Reporter: Peter Eastman
If you do not specify a default value for a property (e.g. with @InitialValue),
it gets initialized to a default value selected by Tapestry. This creates lots
of opportunities for confusion and bugs. I suggest that instead, the property
should be marked internally as "uninitialized". If you attempt to get its
value while it is in that state, it should throw an exception. Looking up a
property before its value has been set is almost always an error. It is much
better to immediately alert the user so they can fix the bug, rather than
letting their program appear to work, but misbehave in some possibly subtle way.
This applies to any situation where you try to access a value that is not
currently available. For example, if you try to access a persistent property
inside pageAttached(), it should throw an exception rather than simply
returning null.
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