[DAFFODIL-2056] Implicit expression conversion from xs:string to xs:hexBinary causes exception

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.2.0
• Fix Version/s: 2.3.0
• Component/s: Front End
• Assignee: Dave Thompson
• Reporter: Steve Lawrence
• Created: 22/Jan/19 15:46
• Updated: 20/May/21 12:34
• Resolved: 29/Jan/19 15:18

Description

Assume the following schema snippet:

<xs:element name="xs:hexBinary" type="xs:hexBinary" dfdl:inputValueCalc="{ xs:string('DEADBEEF') }" />

As of Daffodil 2.3.0, we allow implicit conversions between the result of an expression and the expected type. So this should insert an implicit conversion from xs:string (the resulting type) to xs:hexBinary (the expected type). But this results in the following exception: 

java.lang.ClassCastException: org.apache.daffodil.dpath.XSHexBinary$ cannot be cast to org.apache.daffodil.dpath.RecipeOp
	at org.apache.daffodil.dpath.Conversion$.conversionOps(Conversions.scala:147)
	at org.apache.daffodil.dpath.Expression.conversions$lzycompute(Expression.scala:120)
	at org.apache.daffodil.dpath.Expression.conversions(Expression.scala:117)
	at org.apache.daffodil.dpath.FNOneArgExpr.compiledDPath$lzycompute(Expression.scala:1869)
	at org.apache.daffodil.dpath.FNOneArgExpr.compiledDPath(Expression.scala:1865)
	at org.apache.daffodil.dpath.FunctionCallExpression.compiledDPath$lzycompute(Expression.scala:1317)
	at org.apache.daffodil.dpath.FunctionCallExpression.compiledDPath(Expression.scala:1317)
	at org.apache.daffodil.dpath.WholeExpression.compiledDPath$lzycompute(Expression.scala:636)
	at org.apache.daffodil.dpath.WholeExpression.compiledDPath(Expression.scala:636)
	at org.apache.daffodil.dpath.DFDLPathExpressionParser.compile(DFDLExpressionParser.scala:54)

Eventually this implicit conversion will be disabled, but since it is allowed we should fix this.

The workaround is to be explicit about the conversion, e.g.:

<xs:element name="xs:hexBinary" type="xs:hexBinary" dfdl:inputValueCalc="{ xs:hexBinary(xs:string('DEADBEEF')) }" />