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Allow constant folding to fold equals operator #822

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Merged
merged 1 commit into from
Sep 23, 2025
Merged

Allow constant folding to fold equals operator #822

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46 changes: 46 additions & 0 deletions optimizer/src/main/java/dev/cel/optimizer/optimizers/ConstantFoldingOptimizer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,16 @@ private boolean canFold(CelNavigableMutableExpr navigableExpr) {
&& cond.constant().getKind().equals(CelConstant.Kind.BOOLEAN_VALUE);
}

if (functionName.equals(Operator.EQUALS.getFunction())
|| functionName.equals(Operator.NOT_EQUALS.getFunction())) {
if (mutableCall.args().stream()
.anyMatch(node -> isExprConstantOfKind(node, CelConstant.Kind.BOOLEAN_VALUE))
|| mutableCall.args().stream()
.allMatch(node -> node.getKind().equals(Kind.CONSTANT))) {
return true;
}
}

if (functionName.equals(Operator.IN.getFunction())) {
return canFoldInOperator(navigableExpr);
}
Expand Down Expand Up @@ -393,6 +403,38 @@ private Optional<CelMutableAst> maybePruneBranches(
}
}
}
} else if (function.equals(Operator.EQUALS.getFunction())
|| function.equals(Operator.NOT_EQUALS.getFunction())) {
CelMutableExpr lhs = call.args().get(0);
CelMutableExpr rhs = call.args().get(1);
boolean lhsIsBoolean = isExprConstantOfKind(lhs, CelConstant.Kind.BOOLEAN_VALUE);
boolean rhsIsBoolean = isExprConstantOfKind(rhs, CelConstant.Kind.BOOLEAN_VALUE);
boolean invertCondition = function.equals(Operator.NOT_EQUALS.getFunction());
Optional<CelMutableExpr> replacementExpr = Optional.empty();

if (lhs.getKind().equals(Kind.CONSTANT) && rhs.getKind().equals(Kind.CONSTANT)) {
// If both args are const, don't prune any branches and let maybeFold method evaluate this
// subExpr
return Optional.empty();
} else if (lhsIsBoolean) {
boolean cond = invertCondition != lhs.constant().booleanValue();
replacementExpr =
Optional.of(
cond
? rhs
: CelMutableExpr.ofCall(
CelMutableCall.create(Operator.LOGICAL_NOT.getFunction(), rhs)));
} else if (rhsIsBoolean) {
boolean cond = invertCondition != rhs.constant().booleanValue();
replacementExpr =
Optional.of(
cond
? lhs
: CelMutableExpr.ofCall(
CelMutableCall.create(Operator.LOGICAL_NOT.getFunction(), lhs)));
}

return replacementExpr.map(node -> astMutator.replaceSubtree(mutableAst, node, expr.id()));
}

return Optional.empty();
Expand Down Expand Up @@ -663,6 +705,10 @@ public static Builder newBuilder() {
ConstantFoldingOptions() {}
}

private static boolean isExprConstantOfKind(CelMutableExpr expr, CelConstant.Kind constantKind) {
return expr.getKind().equals(Kind.CONSTANT) && expr.constant().getKind().equals(constantKind);
}

private ConstantFoldingOptimizer(ConstantFoldingOptions constantFoldingOptions) {
this.constantFoldingOptions = constantFoldingOptions;
this.astMutator = AstMutator.newInstance(constantFoldingOptions.maxIterationLimit());
Expand Down
28 changes: 26 additions & 2 deletions optimizer/src/test/java/dev/cel/optimizer/optimizers/ConstantFoldingOptimizerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -66,13 +66,13 @@ public class ConstantFoldingOptimizerTest {
CelExtensions.math(CelOptions.DEFAULT),
CelExtensions.strings(),
CelExtensions.sets(CelOptions.DEFAULT),
CelExtensions.encoders())
CelExtensions.encoders(CelOptions.DEFAULT))
.addRuntimeLibraries(
CelOptionalLibrary.INSTANCE,
CelExtensions.math(CelOptions.DEFAULT),
CelExtensions.strings(),
CelExtensions.sets(CelOptions.DEFAULT),
CelExtensions.encoders())
CelExtensions.encoders(CelOptions.DEFAULT))
.build();

private static final CelOptimizer CEL_OPTIMIZER =
Expand Down Expand Up @@ -189,6 +189,28 @@ public class ConstantFoldingOptimizerTest {
@TestParameters("{source: 'sets.contains([1], [1])', expected: 'true'}")
@TestParameters(
"{source: 'cel.bind(r0, [1, 2, 3], cel.bind(r1, 1 in r0, r1))', expected: 'true'}")
@TestParameters("{source: 'x == true', expected: 'x'}")
@TestParameters("{source: 'true == x', expected: 'x'}")
@TestParameters("{source: 'x == false', expected: '!x'}")
@TestParameters("{source: 'false == x', expected: '!x'}")
@TestParameters("{source: 'true == false', expected: 'false'}")
@TestParameters("{source: 'true == true', expected: 'true'}")
@TestParameters("{source: 'false == true', expected: 'false'}")
@TestParameters("{source: 'false == false', expected: 'true'}")
@TestParameters("{source: '10 == 42', expected: 'false'}")
@TestParameters("{source: '42 == 42', expected: 'true'}")
@TestParameters("{source: 'x != true', expected: '!x'}")
@TestParameters("{source: 'true != x', expected: '!x'}")
@TestParameters("{source: 'x != false', expected: 'x'}")
@TestParameters("{source: 'false != x', expected: 'x'}")
@TestParameters("{source: 'true != false', expected: 'true'}")
@TestParameters("{source: 'true != true', expected: 'false'}")
@TestParameters("{source: 'false != true', expected: 'true'}")
@TestParameters("{source: 'false != false', expected: 'false'}")
@TestParameters("{source: '10 != 42', expected: 'true'}")
@TestParameters("{source: '42 != 42', expected: 'false'}")
@TestParameters("{source: '[\"foo\",\"bar\"] == [\"foo\",\"bar\"]', expected: 'true'}")
@TestParameters("{source: '[\"bar\",\"foo\"] == [\"foo\",\"bar\"]', expected: 'false'}")
// TODO: Support folding lists with mixed types. This requires mutable lists.
// @TestParameters("{source: 'dyn([1]) + [1.0]'}")
public void constantFold_success(String source, String expected) throws Exception {
Expand Down Expand Up @@ -324,6 +346,8 @@ public void constantFold_macros_withoutMacroCallMetadata(String source) throws E
@TestParameters("{source: 'TestAllTypes{single_int32: x, repeated_int32: [1, 2, 3]}'}")
@TestParameters("{source: 'get_true() == get_true()'}")
@TestParameters("{source: 'get_true() == true'}")
@TestParameters("{source: 'x == x'}")
@TestParameters("{source: 'x == 42'}")
public void constantFold_noOp(String source) throws Exception {
CelAbstractSyntaxTree ast = CEL.compile(source).getAst();

Expand Down