I'm trying to get EDIFACT working on Daffodil.

This schema uses dfdl:escapeCharacter and dfdl:escapeEscapeCharacter as expressions. E.g., there is a top-level dfdl:defineVariable named "EscapeChar" which has a default value, and the expression for the dfdl:escapeCharacter property is

.

The default format that is in effect for the root element 'Interchange' has dfdl:lengthKind='delimited'.

When daffodil starts parsing the top level root/document element, it enters a parser that is for delimited elements with an escape-scheme in effect. First thing this parser does is get the escape scheme which evaluates the expressions for escapeCharacter and escapeEscapeCharacter. This picks up the default values for those variables and the variables are then set as "already evaluated", as DFDL specifies that once a variable's default value has been used, it cannot be subsequently set via dfdl:setVariable.

Now, when the very first UNA is encountered, that reads the various delimiters/escapes from the data, and tries to set the variables.

But the variables have already been evaluated, on the way into parsing the "delimited" top level element.

So it fails with a runtime SDE - default value has already been used for EscapeChar variable.

So this clearly a bug.

The principle is that a complex-typed element of length kind delimited when there is no definition of terminator nor applicable separator, that this situation is treated like dfdl:lengthKind='implicit' and the escapeScheme is therefore not relevant and the expressions for the escapeScheme characters MUST NOT be evaluated.

One could argue that the EDIFACT schema should have dfdl:lengthKind='implicit' on the 'Interchange' element and any other complex type element, but this is quite burdensome on the schema author, who after-all thinks of this entire format as "delimited stuff".