[DAFFODIL-1279] Need DPath warnings when paths are not encapsulated with fn:exists(....)

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.0.0
• Component/s: Back End, Diagnostics, Middle "End", Usability
• Assignee: Unassigned
• Reporter: Mike Beckerle
• Created: 18/Mar/15 23:32
• Updated: 16/Dec/20 19:33

Description

Expressions like

{ ../foo/bar eq 3 }

are very error prone. If node ../foo/bar doesn't exist you get a runtime Schema Definition Error, which is fatal, not backtrackable.

Really what is needed is:

{ if fn:exists(../foo/bar) then ../foo/bar eq 3 else daf:error("....") }

The DPath compiler should warn when a path is being used which may not exist, but is not wrapped in fn:exists(....) and if-then-else.

But that may really not be the right warning. Probably such expressions really should be moved to a location in the schema where the elements they are referring to simply must exist. E.g., if the expression was on element bar, or a sub-component within the schema of element bar, then the existence of element bar (and its parent foo) is implied and the expression can't get a runtime SDE.

See also related Bug DFDL-1278.