FailureAction

is an option to Query and related functions that determines what should happen when a failure or message is generated.

Details

	None	ignore all messages and failures
	"Abort"	abort the entire computation when a message is issued
	"Drop"	drop the results of operations that issue messages
	"Encapsulate"	wrap operations that issue messages in a Failure object
	"Replace"	replace with a placeholder form
	{act,f}	perform the action and apply f to the Failure object

With the setting {"Replace",f}, the value generated by applying f to the Failure object is used as the placeholder form.

open allclose all

Create sample data:

The setting FailureActionNone takes no special action on the result:

The setting FailureAction->"Encapsulate" encapsulates failed results in a Failure object:

The setting FailureAction->"Replace" replaces failed results with a placeholder. For the function Query, this placeholder is a Missing object:

The setting FailureAction->"Drop" causes failed results to be dropped from the final expression:

The setting FailureAction->"Abort" aborts the computation, returning a Failure object instead:

The setting FailureAction->{"Drop",f} can be used to perform an action before dropping a failed result:

The setting FailureAction->{"Replace",f} can be used to specify a replacement that is a function of the failure:

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