From 49851f5bed92d2a4c2a2c1a0210b222d20cb2b20 Mon Sep 17 00:00:00 2001
From: Sokwhan Huh <sokwhan@google.com>
Date: Fri, 5 Jun 2026 12:00:40 -0700
Subject: [PATCH] Safely ignore enums in native type extensions

Ref: https://github.com/google/cel-java/issues/1077
PiperOrigin-RevId: 927414521
---
 .../extensions/CelNativeTypesExtensions.java  |  8 ++++
 .../main/java/dev/cel/extensions/README.md    |  1 +
 .../CelNativeTypesExtensionsTest.java         | 47 +++++++++++++++++--
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/extensions/src/main/java/dev/cel/extensions/CelNativeTypesExtensions.java b/extensions/src/main/java/dev/cel/extensions/CelNativeTypesExtensions.java
index ae9483f7c..44fcdd1f6 100644
--- a/extensions/src/main/java/dev/cel/extensions/CelNativeTypesExtensions.java
+++ b/extensions/src/main/java/dev/cel/extensions/CelNativeTypesExtensions.java
@@ -82,6 +82,10 @@ public final class CelNativeTypesExtensions implements CelCompilerLibrary, CelRu
   private static final ImmutableSet<String> OBJECT_METHOD_NAMES =
       stream(Object.class.getDeclaredMethods()).map(Method::getName).collect(toImmutableSet());
 
+  // Set of all standard java.lang.Enum method names.
+  private static final ImmutableSet<String> ENUM_METHOD_NAMES =
+      stream(Enum.class.getDeclaredMethods()).map(Method::getName).collect(toImmutableSet());
+
   private static final ImmutableMap<Class<?>, CelType> JAVA_TO_CEL_TYPE_MAP =
       ImmutableMap.<Class<?>, CelType>builder()
           .put(boolean.class, SimpleType.BOOL)
@@ -606,6 +610,10 @@ private static boolean isGetter(Method method) {
       if (OBJECT_METHOD_NAMES.contains(name)) {
         return false;
       }
+      if (Enum.class.isAssignableFrom(method.getDeclaringClass())
+          && ENUM_METHOD_NAMES.contains(name)) {
+        return false;
+      }
       if (name.startsWith("get")) {
         return name.length() > 3;
       }
diff --git a/extensions/src/main/java/dev/cel/extensions/README.md b/extensions/src/main/java/dev/cel/extensions/README.md
index fcf019d15..5b75bb48d 100644
--- a/extensions/src/main/java/dev/cel/extensions/README.md
+++ b/extensions/src/main/java/dev/cel/extensions/README.md
@@ -1122,6 +1122,7 @@ The type-mapping between Java and CEL is as follows:
 
 *   This is only supported for the planner runtime (e.g., `CelRuntimeFactory.plannerRuntimeBuilder()`).
 *   Native Java arrays (except `byte[]`) are not supported. Use `java.util.List` instead.
+*   Java `enum` properties are not currently supported and will be safely ignored during scanning.
 *   If there is a name collision with a Protobuf type, the protobuf type will take precedence.
 *   Instantiating new struct values (e.g., `Account{id: 1234}`) requires the class to have a no-argument constructor (public, protected, package-private, or private).
 *   Final fields are supported only in a **read-only** capacity; they cannot be populated when instantiating new struct values.
diff --git a/extensions/src/test/java/dev/cel/extensions/CelNativeTypesExtensionsTest.java b/extensions/src/test/java/dev/cel/extensions/CelNativeTypesExtensionsTest.java
index dcd3e811c..5485989af 100644
--- a/extensions/src/test/java/dev/cel/extensions/CelNativeTypesExtensionsTest.java
+++ b/extensions/src/test/java/dev/cel/extensions/CelNativeTypesExtensionsTest.java
@@ -89,7 +89,8 @@ public final class CelNativeTypesExtensionsTest {
           TestNestedSimplePojo.class,
           TestGetterFieldTypeMismatchPojo.class,
           TestAbstractPojo.class,
-          TestURLPojo.class);
+          TestURLPojo.class,
+          PojoWithEnum.class);
 
   private static final Cel CEL =
       CelFactory.plannerCelBuilder()
@@ -564,16 +565,24 @@ public void nativeTypes_prefixLessGetter_success() throws Exception {
             .setContainer(CelContainer.ofName("dev.cel.extensions.CelNativeTypesExtensionsTest"))
             .addLibraries(extensions)
             .build();
-    CelAbstractSyntaxTree ast =
+    CelAbstractSyntaxTree valueAst =
         celCompiler
             .compile(
                 "dev.cel.extensions.CelNativeTypesExtensionsTest.TestPrefixLessGetterPojo{}.value")
             .getAst();
-    CelRuntime.Program program = celRuntime.createProgram(ast);
+    CelAbstractSyntaxTree nameAst =
+        celCompiler
+            .compile(
+                "dev.cel.extensions.CelNativeTypesExtensionsTest.TestPrefixLessGetterPojo{}.name")
+            .getAst();
+    CelRuntime.Program valueProgram = celRuntime.createProgram(valueAst);
+    CelRuntime.Program nameProgram = celRuntime.createProgram(nameAst);
 
-    Object result = program.eval();
+    Object valueResult = valueProgram.eval();
+    Object nameResult = nameProgram.eval();
 
-    assertThat(result).isEqualTo("hello");
+    assertThat(valueResult).isEqualTo("hello");
+    assertThat(nameResult).isEqualTo("my_name");
   }
 
   @Test
@@ -1201,10 +1210,15 @@ public static final class TestPrivateFieldPojo {
 
   public static class TestPrefixLessGetterPojo {
     private String value = "hello";
+    private String name = "my_name";
 
     public String value() {
       return value;
     }
+
+    public String name() {
+      return name;
+    }
   }
 
   public static class TestParentPojo {
@@ -1346,4 +1360,27 @@ public String getMismatchField() {
       return "mismatch";
     }
   }
+
+  public enum TestEnum {
+    FOO,
+    BAR;
+  }
+
+  public static class PojoWithEnum {
+    private TestEnum enumVal = TestEnum.FOO;
+
+    public TestEnum getEnumVal() {
+      return enumVal;
+    }
+
+    public void setEnumVal(TestEnum val) {
+      this.enumVal = val;
+    }
+  }
+
+  @Test
+  public void nativeTypes_enumSafelyIgnored() throws Exception {
+    assertThat(eval("PojoWithEnum{}.enumVal")).isNotNull();
+  }
+
 }