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Add an axiom for optional.ofZeroValue for verifier #1138

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46 changes: 41 additions & 5 deletions verifier/src/main/java/dev/cel/verifier/CelAstToZ3Translator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@
import dev.cel.common.types.ListType;
import dev.cel.common.types.MapType;
import dev.cel.common.types.NullableType;
import dev.cel.common.types.OptionalType;
import dev.cel.common.types.SimpleType;
import dev.cel.common.types.StructType;
import dev.cel.common.types.StructTypeReference;
Expand Down Expand Up @@ -287,9 +288,13 @@ private TranslatedValue translateList(CelExpr celExpr, CelAbstractSyntaxTree ast
for (int i = 0; i < elements.size(); i++) {
CelExpr element = elements.get(i);
TranslatedValue elem = translateExpr(element, ast);
elementsTv.add(elem);

if (optionalIndices.contains(i)) {
Expr<?> checkedValue =
typeSystem.withRuntimeError(
elem.z3Expr(), ctx.mkNot(typeSystem.isOptional(elem.z3Expr())));
elem = TranslatedValue.create(checkedValue, element, typeSystem, elem.isApproximate());

Expr<?> optRef = typeSystem.getOptionalRef(elem.z3Expr());
seq =
(SeqExpr)
Expand All @@ -300,6 +305,7 @@ private TranslatedValue translateList(CelExpr celExpr, CelAbstractSyntaxTree ast
} else {
seq = typeSystem.mkConcatSafe(seq, ctx.mkUnit(elem.z3Expr()));
}
elementsTv.add(elem);
}
listRef = typeSystem.mkListRefConst(LIST_REF_PREFIX);
typeConstraints.add(ctx.mkEq(typeSystem.getSeq(listRef), seq));
Expand Down Expand Up @@ -327,15 +333,20 @@ private TranslatedValue translateMap(CelExpr celExpr, CelAbstractSyntaxTree ast)
elementsTv.add(keyTv);
TranslatedValue valueTv = translateExpr(entryAst.value(), ast);
Expr<?> value = valueTv.z3Expr();
elementsTv.add(valueTv);

Expr<?> finalValue = value;
BoolExpr finalPresence = ctx.mkTrue();
if (entryAst.optionalEntry()) {
Expr<?> optRef = typeSystem.getOptionalRef(value);
Expr<?> checkedValue =
typeSystem.withRuntimeError(value, ctx.mkNot(typeSystem.isOptional(value)));
valueTv =
TranslatedValue.create(
checkedValue, entryAst.value(), typeSystem, valueTv.isApproximate());
Expr<?> optRef = typeSystem.getOptionalRef(checkedValue);
finalPresence = typeSystem.optHasValue(optRef);
finalValue = typeSystem.getOptionalValue(optRef);
}
elementsTv.add(valueTv);

BoolExpr keyAlreadyPresent = (BoolExpr) ctx.mkSelect(mapPresence, key);
BoolExpr shouldInsertKey = ctx.mkAnd(ctx.mkNot(keyAlreadyPresent), finalPresence);
Expand Down Expand Up @@ -382,7 +393,6 @@ private TranslatedValue translateStruct(CelExpr celExpr, CelAbstractSyntaxTree a
Expr<?> key = ctx.mkString(entryAst.fieldKey());
TranslatedValue valueTv = translateExpr(entryAst.value(), ast);
Expr<?> value = valueTv.z3Expr();
elementsTv.add(valueTv);

CelType fieldType =
typeProvider
Expand All @@ -397,10 +407,16 @@ private TranslatedValue translateStruct(CelExpr celExpr, CelAbstractSyntaxTree a
Expr<?> finalValue = value;
BoolExpr optionalHasValue = ctx.mkTrue();
if (entryAst.optionalEntry()) {
Expr<?> optRef = typeSystem.getOptionalRef(value);
Expr<?> checkedValue =
typeSystem.withRuntimeError(value, ctx.mkNot(typeSystem.isOptional(value)));
valueTv =
TranslatedValue.create(
checkedValue, entryAst.value(), typeSystem, valueTv.isApproximate());
Expr<?> optRef = typeSystem.getOptionalRef(checkedValue);
optionalHasValue = typeSystem.optHasValue(optRef);
finalValue = typeSystem.getOptionalValue(optRef);
}
elementsTv.add(valueTv);

// Canonicalization Trick:
//
Expand Down Expand Up @@ -436,6 +452,9 @@ private Expr<?> getDefaultValueForType(CelType type) {
if (type instanceof NullableType) {
return typeSystem.mkNull();
}
if (type instanceof OptionalType) {
return typeSystem.mkOptionalNone();
}
if (type.equals(SimpleType.INT)) {
return typeSystem.mkInt(0);
}
Expand Down Expand Up @@ -1147,6 +1166,23 @@ private BoolExpr createTypeConstraint(Expr<?> val, long exprId, CelAbstractSynta
}

private BoolExpr createTypeConstraintForType(Expr<?> val, CelType type) {
if (type instanceof NullableType) {
NullableType nullableType = (NullableType) type;
return ctx.mkOr(
typeSystem.isNull(val), createTypeConstraintForType(val, nullableType.targetType()));
}
if (type instanceof OptionalType) {
BoolExpr isOpt = typeSystem.isOptional(val);
CelType paramType = type.parameters().get(0);
if (paramType.kind().isDyn() || paramType.kind().isTypeParam()) {
return isOpt;
}
Expr<?> optRef = typeSystem.getOptionalRef(val);
BoolExpr hasValue = typeSystem.optHasValue(optRef);
BoolExpr valConstraint =
createTypeConstraintForType(typeSystem.getOptionalValue(optRef), paramType);
return ctx.mkAnd(isOpt, ctx.mkImplies(hasValue, valConstraint));
}
if (type.equals(SimpleType.BOOL)) {
return (BoolExpr) ctx.mkApp(typeSystem.boolCons().getTesterDecl(), val);
}
Expand Down
17 changes: 17 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 @@ -123,6 +123,23 @@ private static String formatExpr(
return "Error";
} else if (decl.equals(typeSystem.unknownCons().ConstructorDecl())) {
return "Unknown";
} else if (decl.equals(typeSystem.optionalCons().ConstructorDecl())) {
Expr<?> optRef = expr.getArgs()[0];
Expr<?> hasValueExpr =
evaluateStrict(
model,
typeSystem.optHasValue(optRef),
String.format("Z3 failed to evaluate optHasValue natively for %s", optRef));
if (hasValueExpr.isTrue()) {
Expr<?> valueExpr =
evaluateStrict(
model,
typeSystem.getOptionalValue(optRef),
String.format("Z3 failed to evaluate optValue natively for %s", optRef));
return "optional(" + formatExpr(ctx, typeSystem, model, valueExpr) + ")";
} else if (hasValueExpr.isFalse()) {
return "optional.none()";
}
}

return expr.toString();
Expand Down
4 changes: 4 additions & 0 deletions verifier/src/main/java/dev/cel/verifier/CelZ3TypeSystem.java
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Original file line number Diff line number Diff line change
Expand Up @@ -256,6 +256,10 @@ Constructor bytesCons() {
return bytesCons;
}

Constructor optionalCons() {
return optionalCons;
}

/** Creates a CelValue containing a boolean. */
public Expr<?> mkBool(boolean val) {
return ctx.mkApp(boolCons.ConstructorDecl(), ctx.mkBool(val));
Expand Down
38 changes: 38 additions & 0 deletions verifier/src/main/java/dev/cel/verifier/axioms/OptionalAxioms.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,13 +15,19 @@
package dev.cel.verifier.axioms;

import com.google.common.collect.ImmutableList;
import com.microsoft.z3.BoolExpr;
import com.microsoft.z3.Context;
import com.microsoft.z3.Expr;
import com.microsoft.z3.FPExpr;
import com.microsoft.z3.SeqExpr;
import dev.cel.common.CelFunctionDecl;
import dev.cel.extensions.CelOptionalLibrary;
import dev.cel.extensions.CelOptionalLibrary.Function;
import dev.cel.verifier.CelZ3TypeSystem;
import java.util.Optional;

/** Axiomatization for CEL's optional library functions. */
@SuppressWarnings({"unchecked", "rawtypes"}) // Z3 Java API uses raw types.
final class OptionalAxioms {

static final ImmutableList<CelZ3FunctionAxiom> ALL_AXIOMS =
Expand All @@ -40,6 +46,17 @@ final class OptionalAxioms {
sink.accept(ts.optHasValue(optRef));
return Optional.of(ts.mkOptionalOf(optRef));
}),
createUnaryAxiom(
Function.OPTIONAL_OF_NON_ZERO_VALUE,
"optional_ofNonZeroValue",
(ctx, ts, sink, value) -> {
Expr<?> optRef = ctx.mkApp(ts.optionalOfRefFunc(), value);
BoolExpr isZero = isZeroValue(ctx, ts, value);
sink.accept(
ctx.mkImplies(ctx.mkNot(isZero), ctx.mkEq(ts.getOptionalValue(optRef), value)));
sink.accept(ctx.mkImplies(ctx.mkNot(isZero), ts.optHasValue(optRef)));
return Optional.of(ctx.mkITE(isZero, ts.mkOptionalNone(), ts.mkOptionalOf(optRef)));
}),
createUnaryAxiom(
Function.HAS_VALUE,
"optional_hasValue",
Expand Down Expand Up @@ -69,6 +86,27 @@ final class OptionalAxioms {
return Optional.of(ctx.mkITE(ts.optHasValue(optRef), val, other));
}));

private static BoolExpr isZeroValue(Context ctx, CelZ3TypeSystem ts, Expr<?> val) {
return ctx.mkOr(
ts.isNull(val),
ctx.mkAnd(ts.isBool(val), ctx.mkEq(ts.unwrapBool(val), ctx.mkFalse())),
ctx.mkAnd(ts.isInt(val), ctx.mkEq(ts.getInt(val), ctx.mkInt(0))),
ctx.mkAnd(ts.isUint(val), ctx.mkEq(ts.getUint(val), ctx.mkInt(0))),
ctx.mkAnd(ts.isDouble(val), ctx.mkFPIsZero((FPExpr) ts.getDouble(val))),
ctx.mkAnd(ts.isString(val), ctx.mkEq(ts.getString(val), ctx.mkString(""))),
ctx.mkAnd(
ts.isBytes(val), ctx.mkEq(ctx.mkLength((SeqExpr) ts.getBytes(val)), ctx.mkInt(0))),
ctx.mkAnd(
ts.isList(val), ctx.mkEq(ctx.mkLength(ts.getSeq(ts.getListRef(val))), ctx.mkInt(0))),
ctx.mkAnd(
ts.isMap(val), ctx.mkEq(ctx.mkLength(ts.getMapKeys(ts.getMapRef(val))), ctx.mkInt(0))),
ctx.mkAnd(
ts.isMessage(val),
ctx.mkEq(
ts.getMsgPresence(ts.getMessageRef(val)),
ctx.mkConstArray(ctx.getStringSort(), ctx.mkFalse()))));
}

private static CelFunctionDecl getDecl(Function funcEnum) {
return CelOptionalLibrary.INSTANCE.functions().stream()
.filter(d -> d.name().equals(funcEnum.getFunction()))
Expand Down
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