[DAFFODIL-1905] fn:error all args assumed to be string, but 3rd arg isn't supposed to have to be a string.

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.1.0
• Component/s: Middle "End"
• Labels: beginner
• Assignee: Unassigned
• Reporter: Mike Beckerle
• Created: 16/Feb/18 20:14
• Updated: 30/Jul/20 22:04

Description

Found when removing deprecated daf:error() from gif schema, and adding in an initial test.

If you have an element of complex type like:

<xs:element name="Header">
		<xs:complexType>
			<xs:sequence>
				<xs:sequence dfdl:hiddenGroupRef="hidden_GIF_Signature_Group" />
				<xs:element name='Signature' type='xs:string' dfdl:inputValueCalc='{
					if (xs:string(../Hidden_Signature) eq "474946") then "GIF"    
					else fn:error("gif", "fn:error called.",  .) <!-- LOOK HERE -->
					}' />
     ...

The fn:error function call won't compile because of its 3 arguments, the third argument which is a "." meaning "this element", errors with

Caused by: Schema Definition Error: The type Complex cannot be converted to String.
Schema context: element reference {}Global_Color_Table Location line 50 column 18 in file:/home/mbeckerle-unencrypted/DFDLSchemas/gif/bin/com/mitre/gif/xsd/gif.dfdl.xsd

The daffodil implementation of fn:error says all 3 arguments are type String. This third argument is type Any. It's documented to be "the object causing the error" in XPath.

A fix will loosen this restriction, allowing that 3rd argument to be anything. Of course it then has to accept and do something with anything there.

In particular, if a complex type element is passed there, it has to do something meaningful.