Support empty message creation

Author: l46kok

common/src/main/java/dev/cel/common/values/BUILD.bazel

@@ -293,6 +293,7 @@ java_library(
         ":proto_message_lite_value",
         "//common:error_codes",
         "//common:runtime_exception",
+        "//common/internal:cel_lite_descriptor_pool",
         "//common/internal:default_instance_message_lite_factory",
         "//common/internal:default_lite_descriptor_pool",
         "//common/internal:proto_lite_adapter",

common/src/main/java/dev/cel/common/values/ProtoMessageLiteValueProvider.java

@@ -16,8 +16,11 @@
 
 import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.annotations.Immutable;
+import com.google.protobuf.MessageLite;
+import dev.cel.common.internal.CelLiteDescriptorPool;
 import dev.cel.common.internal.DefaultLiteDescriptorPool;
 import dev.cel.protobuf.CelLiteDescriptor;
+import dev.cel.protobuf.CelLiteDescriptor.MessageLiteDescriptor;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
@@ -30,6 +33,7 @@
  */
 @Immutable
 public class ProtoMessageLiteValueProvider implements CelValueProvider {
+  private final CelLiteDescriptorPool descriptorPool;
   private final ProtoLiteCelValueConverter protoLiteCelValueConverter;
 
   public ProtoLiteCelValueConverter getProtoLiteCelValueConverter() {
@@ -38,7 +42,17 @@ public ProtoLiteCelValueConverter getProtoLiteCelValueConverter() {
 
   @Override
   public Optional<CelValue> newValue(String structType, Map<String, Object> fields) {
-    throw new UnsupportedOperationException("Message creation is not supported yet.");
+    MessageLiteDescriptor descriptor = descriptorPool.findDescriptor(structType).orElse(null);
+    if (descriptor == null) {
+      return Optional.empty();
+    }
+
+    if (!fields.isEmpty()) {
+      throw new UnsupportedOperationException("Message creation with prepopulated fields is not supported yet.");
+    }
+
+    MessageLite message = descriptor.newMessageBuilder().build();
+    return Optional.of(protoLiteCelValueConverter.fromProtoMessageToCelValue(structType, message));
   }
 
 
@@ -51,11 +65,13 @@ public static ProtoMessageLiteValueProvider newInstance(Set<CelLiteDescriptor> d
     DefaultLiteDescriptorPool descriptorPool = DefaultLiteDescriptorPool.newInstance(ImmutableSet.copyOf(descriptors));
     ProtoLiteCelValueConverter protoLiteCelValueConverter =
         ProtoLiteCelValueConverter.newInstance(descriptorPool);
-    return new ProtoMessageLiteValueProvider(protoLiteCelValueConverter);
+    return new ProtoMessageLiteValueProvider(protoLiteCelValueConverter, descriptorPool);
   }
 
   private ProtoMessageLiteValueProvider(
-      ProtoLiteCelValueConverter protoLiteCelValueConverter) {
+      ProtoLiteCelValueConverter protoLiteCelValueConverter,
+      CelLiteDescriptorPool descriptorPool) {
     this.protoLiteCelValueConverter = protoLiteCelValueConverter;
+    this.descriptorPool = descriptorPool;
   }
 }

runtime/src/test/java/dev/cel/runtime/CelLiteDescriptorEvaluationTest.java

@@ -81,12 +81,23 @@ public class CelLiteDescriptorEvaluationTest {
           .build();
 
   @Test
-  public void messageCreation_throws() throws Exception {
+  public void messageCreation_emptyMessage() throws Exception {
     CelAbstractSyntaxTree ast = CEL_COMPILER.compile("TestAllTypes{}").getAst();
 
+    TestAllTypes simpleTest = (TestAllTypes) CEL_RUNTIME.createProgram(ast).eval();
+
+    assertThat(simpleTest).isEqualTo(TestAllTypes.getDefaultInstance());
+  }
+
+  @Test
+  public void messageCreation_fieldsPopulated() throws Exception {
+    CelAbstractSyntaxTree ast = CEL_COMPILER.compile("TestAllTypes{single_int32: 4}").getAst();
+
     CelEvaluationException e = assertThrows(CelEvaluationException.class, () -> CEL_RUNTIME.createProgram(ast).eval());
-    assertThat(e).hasCauseThat().hasMessageThat().contains("Message creation is not supported yet.");
+
+    assertThat(e.getMessage()).contains("Message creation with prepopulated fields is not supported yet.");
   }
+
   @Test
   @TestParameters("{expression: 'msg.single_int32 == 1'}")
   @TestParameters("{expression: 'msg.single_int64 == 2'}")
@@ -403,7 +414,7 @@ public void presenceTest_evaluatesToTrue(String expression) throws Exception {
   }
 
   @Test
-  public void nestedMessage() throws Exception {
+  public void nestedMessage_traversalThroughSetField() throws Exception {
     CelAbstractSyntaxTree ast =
         CEL_COMPILER
             .compile("msg.single_nested_message.bb == 43 && has(msg.single_nested_message)")
@@ -419,6 +430,23 @@ public void nestedMessage() throws Exception {
     assertThat(result).isTrue();
   }
 
+  @Test
+  public void nestedMessage_safeTraversal() throws Exception {
+    CelAbstractSyntaxTree ast =
+        CEL_COMPILER
+            .compile("msg.single_nested_message.bb == 43")
+            .getAst();
+    TestAllTypes nestedMessage =
+        TestAllTypes.newBuilder()
+            .setSingleNestedMessage(NestedMessage.getDefaultInstance())
+            .build();
+
+    boolean result =
+        (boolean) CEL_RUNTIME.createProgram(ast).eval(ImmutableMap.of("msg", nestedMessage));
+
+    assertThat(result).isFalse();
+  }
+
   @Test
   public void enumSelection() throws Exception {
     CelAbstractSyntaxTree ast = CEL_COMPILER.compile("msg.single_nested_enum").getAst();