Aklakan commented on code in PR #2413:
URL: https://github.com/apache/jena/pull/2413#discussion_r1568854343
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jena-arq/src/main/java/org/apache/jena/sparql/engine/main/VarFinder.java:
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@@ -329,12 +336,43 @@ public void visit(OpExtend opExtend) {
private void processAssignVarExprList(VarExprList varExprList) {
varExprList.forEachVarExpr((v,e)-> {
- defines.add(v) ; // Expression may eval to error -> unset?
- if ( e != null )
+ if ( e != null ) {
+ boolean isLikelyToBeDefined = isLikelyToBeDefined(e);
+ if (isLikelyToBeDefined) {
+ defines.add(v) ; // Expression may eval to error ->
unset?
+ }
ExprVars.nonOpVarsMentioned(assignMentions, e);
+ }
}) ;
}
+ /**
+ * Heuristic to check whether the expression's evaluation result is
likely
+ * to always be defined (i.e. never null / type error).
+ * Does not detect runtime type errors, such as when
+ * expr is (?x < 1) and ?x is assigned a string.
+ */
+ private boolean isLikelyToBeDefined(Expr expr) {
+ boolean result;
+ if (expr.isVariable()) {
+ result = defines.contains(expr.asVar());
+ } else if (expr.isConstant() || expr instanceof E_Bound) {
+ result = true;
+ } else if (expr.isFunction()) {
+ ExprFunction fn = expr.getFunction();
+ List<Expr> args = fn.getArgs();
+ if (fn instanceof E_Coalesce) {
+ result = args.stream().anyMatch(this::isLikelyToBeDefined);
Review Comment:
Done
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