stevedlawrence commented on a change in pull request #214: Sequences and
Separators Refactoring and Rewrite
URL: https://github.com/apache/incubator-daffodil/pull/214#discussion_r285125748
##########
File path:
daffodil-core/src/main/scala/org/apache/daffodil/dsom/LocalElementMixin.scala
##########
@@ -74,20 +74,42 @@ trait LocalElementMixin
res
}.value
- final override def hasKnownRequiredSyntax: Boolean =
LV('hasKnownRequiredSyntax) {
- !couldBeMissing
- }.value
+ final override def hasKnownRequiredSyntax: Boolean = !couldBeMissing
- final def couldBeMissing: Boolean = LV('couldBeMissing) {
+ final lazy val couldBeMissing: Boolean = LV('couldBeMissing) {
val res =
if (minOccurs == 0) true
else if (isNillable && !hasNilValueRequiredSyntax) true
else if (isDefaultable && emptyValueDelimiterPolicy =:=
EmptyValueDelimiterPolicy.None) true
else if (isDefaultable && !hasInitiator && emptyValueDelimiterPolicy =:=
EmptyValueDelimiterPolicy.Initiator) true
else if (isDefaultable && !hasTerminator && emptyValueDelimiterPolicy
=:= EmptyValueDelimiterPolicy.Terminator) true
- else if (hasInitiator) false
- else if (hasTerminator) false
- else if (isSimpleType) {
+ else if (hasInitiator) {
+ //
+ // TODO: It is possible that this constant expression cannot match
zero length
+ // or that it can match zero length. We don't really know without
analyzing it.
+ // The easiest way may be at compile time to try matching it against
an empty string.
+ // That would tell us whether it requires input or not.
+ //
+ // For now we just assume if it has an initiator, then it can't be
missing.
+ false
+ } else if (hasTerminator) {
+ // If the lengthKind is NOT delimited, then the terminator is
potentially redundant and
+ // there are real formats (mil-std-2045) where the terminator is an
expression, but that expression
+ // returns %WSP*; or %ES;, meaning the terminator can match zero
length.
+ if (!terminatorExpr.isConstant && (lengthKind ne
LengthKind.Delimited)) {
+ //
+ // It seems like we could do better here if we actually looked at
the expression to see
+ // if it can be zero length. But we don't necessarily know because
the expression could
+ // refer to other infoset contents
+ true // this is in fact the case for mil-std-2045 tString32 type. It
uses the length of another element to decide
Review comment:
Weird to have true in the middle of a comment.
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