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Make counterexample generator resilient against self references #1426

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Merged
copybara-service merged 1 commit into from
Oct 28, 2026
Merged

Make counterexample generator resilient against self references #1426

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12 changes: 12 additions & 0 deletions verifier/src/main/java/dev/cel/verifier/CelZ3CounterexampleGenerator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ final class CelZ3CounterexampleGenerator {
private final Context ctx;
private final CelZ3TypeSystem typeSystem;
private final Model model;
private final Set<Expr<?>> valuesOnPath;

static String generate(
Context ctx,
Expand Down Expand Up @@ -78,6 +79,16 @@ static String generate(

// Formats a model value as a CEL literal where one exists.
private String format(Expr<?> expr) {
// Refs are uninterpreted, so Z3 may return a cyclic model (e.g. a map containing itself).
if (!valuesOnPath.add(expr)) {
return "<cycle>";
}
String formatted = formatValue(expr);
valuesOnPath.remove(expr);
return formatted;
}

private String formatValue(Expr<?> expr) {
FuncDecl decl = expr.getFuncDecl();
Expr<?>[] args = expr.getArgs();

Expand Down Expand Up @@ -274,5 +285,6 @@ private CelZ3CounterexampleGenerator(Context ctx, CelZ3TypeSystem typeSystem, Mo
this.ctx = ctx;
this.typeSystem = typeSystem;
this.model = model;
this.valuesOnPath = new HashSet<>();
}
}
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