Enhance ConstantFoldingOptimizer to fold arithmetics involving timestamps and durations by copybara-service[bot] · Pull Request #825 · cel-expr/cel-java · GitHub
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Enhance ConstantFoldingOptimizer to fold arithmetics involving timestamps and durations #825

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Merged
copybara-service merged 1 commit into from
Oct 1, 2025
Merged

Enhance ConstantFoldingOptimizer to fold arithmetics involving timestamps and durations #825

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2 changes: 1 addition & 1 deletion checker/src/main/java/dev/cel/checker/CelStandardDeclarations.java
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2 changes: 2 additions & 0 deletions optimizer/src/main/java/dev/cel/optimizer/optimizers/BUILD.bazel
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,14 @@ java_library(
":default_optimizer_constants",
"//:auto_value",
"//bundle:cel",
"//checker:standard_decl",
"//common:cel_ast",
"//common:cel_source",
"//common:compiler_common",
"//common:mutable_ast",
"//common/ast",
"//common/ast:mutable_expr",
"//common/internal:date_time_helpers",
"//common/navigation:mutable_navigation",
"//common/types",
"//extensions:optional_library",
Expand Down
45 changes: 37 additions & 8 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 @@ -16,6 +16,8 @@
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.ImmutableList.toImmutableList;
import static com.google.common.collect.MoreCollectors.onlyElement;
import static dev.cel.checker.CelStandardDeclarations.StandardFunction.DURATION;
import static dev.cel.checker.CelStandardDeclarations.StandardFunction.TIMESTAMP;

import com.google.auto.value.AutoValue;
import com.google.common.collect.ImmutableList;
Expand All @@ -36,6 +38,7 @@
import dev.cel.common.ast.CelMutableExpr.CelMutableMap;
import dev.cel.common.ast.CelMutableExpr.CelMutableStruct;
import dev.cel.common.ast.CelMutableExprConverter;
import dev.cel.common.internal.DateTimeHelpers;
import dev.cel.common.navigation.CelNavigableMutableAst;
import dev.cel.common.navigation.CelNavigableMutableExpr;
import dev.cel.common.types.SimpleType;
Expand All @@ -45,6 +48,8 @@
import dev.cel.optimizer.CelOptimizationException;
import dev.cel.parser.Operator;
import dev.cel.runtime.CelEvaluationException;
import java.time.Duration;
import java.time.Instant;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
Expand Down Expand Up @@ -142,6 +147,14 @@ private boolean canFold(CelNavigableMutableExpr navigableExpr) {
return false;
}

// Timestamps/durations in CEL are calls, but they are effectively treated as literals.
// Expressions like timestamp(123) cannot be folded directly, but arithmetics involving
// timestamps can be optimized.
// Ex: timestamp(123) - timestamp(100) = duration("23s")
if (isCallTimestampOrDuration(navigableExpr.expr().call())) {
return false;
}

CelMutableCall mutableCall = navigableExpr.expr().call();
String functionName = mutableCall.function();

Expand Down Expand Up @@ -197,14 +210,14 @@ private boolean canFold(CelNavigableMutableExpr navigableExpr) {
private boolean containsFoldableFunctionOnly(CelNavigableMutableExpr navigableExpr) {
return navigableExpr
.allNodes()
.allMatch(
node -> {
if (node.getKind().equals(Kind.CALL)) {
return foldableFunctions.contains(node.expr().call().function());
}

return true;
});
.filter(node -> node.getKind().equals(Kind.CALL))
.map(node -> node.expr().call())
.allMatch(call -> foldableFunctions.contains(call.function()));
}

private static boolean isCallTimestampOrDuration(CelMutableCall call) {
return call.function().equals(TIMESTAMP.functionName())
|| call.function().equals(DURATION.functionName());
}

private static boolean canFoldInOperator(CelNavigableMutableExpr navigableExpr) {
Expand Down Expand Up @@ -318,6 +331,22 @@ private Optional<CelMutableExpr> maybeAdaptEvaluatedResult(Object result) {
}

return Optional.of(CelMutableExpr.ofMap(CelMutableMap.create(mapEntries)));
} else if (result instanceof Duration) {
String durationStrArg = DateTimeHelpers.toString((Duration) result);
CelMutableCall durationCall =
CelMutableCall.create(
DURATION.functionName(),
CelMutableExpr.ofConstant(CelConstant.ofValue(durationStrArg)));

return Optional.of(CelMutableExpr.ofCall(durationCall));
} else if (result instanceof Instant) {
String timestampStrArg = result.toString();
CelMutableCall timestampCall =
CelMutableCall.create(
TIMESTAMP.functionName(),
CelMutableExpr.ofConstant(CelConstant.ofValue(timestampStrArg)));

return Optional.of(CelMutableExpr.ofCall(timestampCall));
}

// Evaluated result cannot be folded (e.g: unknowns)
Expand Down
29 changes: 23 additions & 6 deletions optimizer/src/test/java/dev/cel/optimizer/optimizers/ConstantFoldingOptimizerTest.java
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