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Add optional pruning operator (?foo) handling to CEL Java's verifier #1131

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Merged
copybara-service merged 1 commit into from
Jul 22, 2026
Merged

Add optional pruning operator (?foo) handling to CEL Java's verifier #1131

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4 changes: 3 additions & 1 deletion verifier/src/main/java/dev/cel/verifier/CelAstAlphaHasher.java
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Original file line number Diff line number Diff line change
Expand Up @@ -118,7 +118,9 @@ private static void hashAst(CelExpr expr, @Nullable Scope scope, HasherContext c
break;
case LIST:
context.hasher.putInt(expr.list().elements().size());
for (CelExpr elem : expr.list().elements()) {
for (int i = 0; i < expr.list().elements().size(); i++) {
CelExpr elem = expr.list().elements().get(i);
context.hasher.putBoolean(expr.list().optionalIndices().contains(i));
hashAst(elem, scope, context);
}
break;
Expand Down
57 changes: 47 additions & 10 deletions verifier/src/main/java/dev/cel/verifier/CelAstToZ3Translator.java
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Expand Up @@ -284,11 +284,24 @@ private TranslatedValue translateList(CelExpr celExpr, CelAbstractSyntaxTree ast
// check to a trivial identity check (e.g., `list_ref_0 == list_ref_0`).
if (listRef == null) {
SeqExpr seq = ctx.mkEmptySeq(ctx.mkSeqSort(typeSystem.celValueSort()));
for (CelExpr element : createList.elements()) {
ImmutableList<Integer> optionalIndices = createList.optionalIndices();
ImmutableList<CelExpr> elements = createList.elements();
for (int i = 0; i < elements.size(); i++) {
CelExpr element = elements.get(i);
TranslatedValue elem = translateExpr(element, ast);
elementsTv.add(elem);

seq = typeSystem.mkConcatSafe(seq, ctx.mkUnit(elem.z3Expr()));
if (optionalIndices.contains(i)) {
Expr<?> optRef = typeSystem.getOptionalRef(elem.z3Expr());
seq =
(SeqExpr)
ctx.mkITE(
typeSystem.optHasValue(optRef),
typeSystem.mkConcatSafe(seq, ctx.mkUnit(typeSystem.getOptionalValue(optRef))),
seq);
} else {
seq = typeSystem.mkConcatSafe(seq, ctx.mkUnit(elem.z3Expr()));
}
}
listRef = typeSystem.mkListRefConst(LIST_REF_PREFIX);
typeConstraints.add(ctx.mkEq(typeSystem.getSeq(listRef), seq));
Expand Down Expand Up @@ -318,12 +331,24 @@ private TranslatedValue translateMap(CelExpr celExpr, CelAbstractSyntaxTree ast)
Expr<?> value = valueTv.z3Expr();
elementsTv.add(valueTv);

Expr<?> finalValue = value;
BoolExpr finalPresence = ctx.mkTrue();
if (entryAst.optionalEntry()) {
Expr<?> optRef = typeSystem.getOptionalRef(value);
finalPresence = typeSystem.optHasValue(optRef);
finalValue = typeSystem.getOptionalValue(optRef);
}

BoolExpr keyAlreadyPresent = (BoolExpr) ctx.mkSelect(mapPresence, key);
BoolExpr shouldInsertKey = ctx.mkAnd(ctx.mkNot(keyAlreadyPresent), finalPresence);
keysSeq =
ctx.mkITE(keyAlreadyPresent, keysSeq, typeSystem.mkConcatSafe(keysSeq, ctx.mkUnit(key)));
ctx.mkITE(shouldInsertKey, typeSystem.mkConcatSafe(keysSeq, ctx.mkUnit(key)), keysSeq);

mapValues = ctx.mkStore(mapValues, key, value);
mapPresence = ctx.mkStore(mapPresence, key, ctx.mkTrue());
mapValues =
(ArrayExpr) ctx.mkITE(finalPresence, ctx.mkStore(mapValues, key, finalValue), mapValues);
mapPresence =
(ArrayExpr)
ctx.mkITE(finalPresence, ctx.mkStore(mapPresence, key, ctx.mkTrue()), mapPresence);
}

typeConstraints.add(ctx.mkEq(typeSystem.getMapValues(mapRef), mapValues));
Expand Down Expand Up @@ -371,6 +396,14 @@ private TranslatedValue translateStruct(CelExpr celExpr, CelAbstractSyntaxTree a
.orElseGet(() -> extractAstTypeOrDefault(ast, entryAst.value().id()));
Expr<?> defaultVal = getDefaultValueForType(fieldType);

Expr<?> finalValue = value;
BoolExpr optionalHasValue = ctx.mkTrue();
if (entryAst.optionalEntry()) {
Expr<?> optRef = typeSystem.getOptionalRef(value);
optionalHasValue = typeSystem.optHasValue(optRef);
finalValue = typeSystem.getOptionalValue(optRef);
}

// Canonicalization Trick:
//
// We avoid storing explicit default values (e.g. `single_int32: 0`)
Expand All @@ -379,11 +412,13 @@ private TranslatedValue translateStruct(CelExpr celExpr, CelAbstractSyntaxTree a
// (`msg1 == msg2`) to work without using quantifiers (which avoids MBQI loops).
// Because proto3 singular primitives do not have field presence, we also skip setting
// `msgPresence`.
BoolExpr shouldBypass =
fieldType.kind().isPrimitive() ? ctx.mkEq(value, defaultVal) : ctx.mkFalse();
BoolExpr isDefaultPrimitive =
fieldType.kind().isPrimitive() ? ctx.mkEq(finalValue, defaultVal) : ctx.mkFalse();

BoolExpr shouldBypass = ctx.mkOr(ctx.mkNot(optionalHasValue), isDefaultPrimitive);

msgValues =
(ArrayExpr) ctx.mkITE(shouldBypass, msgValues, ctx.mkStore(msgValues, key, value));
(ArrayExpr) ctx.mkITE(shouldBypass, msgValues, ctx.mkStore(msgValues, key, finalValue));

msgPresence =
(ArrayExpr)
Expand Down Expand Up @@ -655,7 +690,8 @@ private TranslatedValue translateComprehension(CelExpr celExpr, CelAbstractSynta
List<Expr<?>> allRangeElems = new ArrayList<>();

// For statically known list/map literals, unroll them exactly.
if (iterRangeExpr.exprKind().getKind() == ExprKind.Kind.LIST) {
if (iterRangeExpr.exprKind().getKind() == ExprKind.Kind.LIST
&& iterRangeExpr.list().optionalIndices().isEmpty()) {
ImmutableList<CelExpr> elements = iterRangeExpr.list().elements();
for (int i = 0; i < elements.size(); i++) {
TranslatedValue valueTv = translateExpr(elements.get(i), ast);
Expand All @@ -664,7 +700,8 @@ private TranslatedValue translateComprehension(CelExpr celExpr, CelAbstractSynta
iterationElements.add(new IterationElement(typeSystem.mkInt(i), value));
allRangeElems.add(value);
}
} else if (iterRangeExpr.exprKind().getKind() == ExprKind.Kind.MAP) {
} else if (iterRangeExpr.exprKind().getKind() == ExprKind.Kind.MAP
&& iterRangeExpr.map().entries().stream().noneMatch(CelExpr.CelMap.Entry::optionalEntry)) {
for (CelExpr.CelMap.Entry entry : iterRangeExpr.map().entries()) {
TranslatedValue keyTv = translateExpr(entry.key(), ast);
Expr<?> key = keyTv.z3Expr();
Expand Down
13 changes: 11 additions & 2 deletions verifier/src/main/java/dev/cel/verifier/CelZ3OperatorTranslator.java
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Expand Up @@ -497,6 +497,11 @@ private BoolExpr getDynamicNumericEquality(Expr<?> z3Expr0, Expr<?> z3Expr1) {
.build(ctx.mkFalse());
}

private boolean hasOptionalElements(TranslatedValue arg) {
return arg.isLiteral(ExprKind.Kind.LIST)
&& !arg.celExpr().get().list().optionalIndices().isEmpty();
}

private BoolExpr unrollListEquality(
TranslatedValue listA, TranslatedValue listB, CelAbstractSyntaxTree ast) {
CelExpr literalListAst =
Expand Down Expand Up @@ -544,7 +549,9 @@ private TranslatedValue translateEquality(
equality = getNumericEquality(arg0, arg1, ast);
} else if (type0.kind() == CelKind.LIST
&& type1.kind() == CelKind.LIST
&& (arg0.isLiteral(ExprKind.Kind.LIST) || arg1.isLiteral(ExprKind.Kind.LIST))) {
&& (arg0.isLiteral(ExprKind.Kind.LIST) || arg1.isLiteral(ExprKind.Kind.LIST))
&& !hasOptionalElements(arg0)
&& !hasOptionalElements(arg1)) {
equality = unrollListEquality(arg0, arg1, ast);
} else if (isStaticallyKnown(type0) && isStaticallyKnown(type1)) {
equality = typeSystem.getStructuralEquality(z3Arg0, z3Arg1);
Expand All @@ -554,7 +561,9 @@ private TranslatedValue translateEquality(

// Check if one side is an explicit LIST that we can unroll
BoolExpr structuralEq = typeSystem.getStructuralEquality(z3Arg0, z3Arg1);
if (arg0.isLiteral(ExprKind.Kind.LIST) || arg1.isLiteral(ExprKind.Kind.LIST)) {
if ((arg0.isLiteral(ExprKind.Kind.LIST) || arg1.isLiteral(ExprKind.Kind.LIST))
&& !hasOptionalElements(arg0)
&& !hasOptionalElements(arg1)) {
structuralEq =
(BoolExpr)
ctx.mkITE(
Expand Down
14 changes: 13 additions & 1 deletion verifier/src/test/java/dev/cel/verifier/CelVerifierZ3ImplTest.java
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Expand Up @@ -42,6 +42,7 @@
import dev.cel.common.ast.CelExpr.CelCall;
import dev.cel.common.types.ListType;
import dev.cel.common.types.MapType;
import dev.cel.common.types.OptionalType;
import dev.cel.common.types.ProtoMessageTypeProvider;
import dev.cel.common.types.SimpleType;
import dev.cel.common.types.StructTypeReference;
Expand Down Expand Up @@ -100,6 +101,7 @@ public final class CelVerifierZ3ImplTest {
.addVar("dyn_map", MapType.create(SimpleType.DYN, SimpleType.DYN))
.addVar("dyn_var", SimpleType.DYN)
.addVar("dyn_var2", SimpleType.DYN)
.addVar("opt_var", OptionalType.create(SimpleType.INT))
.addVar("string_int_map", MapType.create(SimpleType.STRING, SimpleType.INT))
.addVar("bytes_val", SimpleType.BYTES)
.addVar(
Expand Down Expand Up @@ -1420,7 +1422,15 @@ private enum EquivalenceTestCase {
"has(dyn({'a': 1}).a) && has(dyn(TestAllTypes{single_int32: 1}).single_int32)"),
DYNAMIC_INDEXING_TYPE_MISMATCH(
"type(request) == type(1) && request[1] == 1 && request[2] == 2",
"type(request) == type(1) && 1 / 0 == 1 && request[2] == 2");
"type(request) == type(1) && 1 / 0 == 1 && request[2] == 2"),
OPTIONAL_PRUNE_LIST_LITERAL("[1, ?optional.of(3)]", "[1,3]"),
OPTIONAL_PRUNE_LIST_NONE("[?optional.none(), ?opt_var]", "[?opt_var]"),
OPTIONAL_PRUNE_MAP_NONE("{?1: optional.none()}", "{}"),
OPTIONAL_PRUNE_STRUCT_LIST(
"TestAllTypes{?repeated_int32: optional.of([1, 2])}",
"cel.expr.conformance.proto3.TestAllTypes{repeated_int32: [1, 2]}"),
OPTIONAL_PRUNE_LIST_EQUALITY("[?optional.none(), 1] == [1]", "true"),
OPTIONAL_PRUNE_LIST_COMPREHENSION("[1, ?optional.none()].all(x, x > 0)", "true");

private final String exprA;
private final String exprB;
Expand Down Expand Up @@ -1458,11 +1468,13 @@ private enum EquivalenceViolationTestCase {
HETEROGENEOUS_FIELD_SELECTION(
"test_all_types.single_int32 == 10", "test_all_types.single_int64 == 10"),
STRUCT_VARIABLE_NOT_EQUIVALENT_TO_DEFAULT("test_all_types == TestAllTypes{}", "true"),
OPTIONAL_INVALID_PRUNE_OPT_VAR("[1, ?opt_var]", "[1]"),
CROSS_TYPE_NUMERIC_INEQUALITY_INT_DOUBLE("request == 1.0", "request == 2.0 || request == 1"),
CROSS_TYPE_SYMBOLIC_INEQUALITY_INT_UINT("dyn(x) == dyn(u)", "false"),
CROSS_TYPE_SYMBOLIC_INEQUALITY_UINT_INT("dyn(u) == dyn(x)", "false"),
OPTIONAL_OR_VALUE_VIOLATION("optional.of(x).orValue(y)", "y"),
OPTIONAL_VALUE_VIOLATION("optional.of(x).value()", "y"),
LIST_OPTIONAL_ELEMENTS_COLLISION("[1, ?opt_var]", "[1, opt_var]"),
CROSS_NUMERIC_EQUALITY_INT_DYN_VIOLATION("1 == request", "false");

final String exprA;
Expand Down
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