Introduce MessageReflector to enable alternative protobuf runtimes

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,43 @@
+// Copyright 2023-2024 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages and, along with their {@link
+ * com.google.protobuf.Descriptors.Descriptor}s, protovalidate-java will be able to validate them.
+ */
+public interface MessageReflector {
+  /**
+   * Whether the wrapped message has the field described by the provided field descriptor.
+   *
+   * @param field The field descriptor to check for.
+   * @return Whether the field is present.
+   */
+  boolean hasField(FieldDescriptor field);
+
+  /**
+   * Get the value described by the provided field descriptor.
+   *
+   * @param field The field descriptor for which to retrieve a value.
+   * @return The value corresponding to the field descriptor.
+   */
+  Value getField(FieldDescriptor field);
+}

src/main/java/build/buf/protovalidate/internal/evaluator/Value.java → src/main/java/build/buf/protovalidate/Value.java

@@ -12,9 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package build.buf.protovalidate.internal.evaluator;
+package build.buf.protovalidate;
 
-import com.google.protobuf.Message;
 import java.util.List;
 import java.util.Map;
 import javax.annotation.Nullable;
@@ -25,22 +24,13 @@
  */
 public interface Value {
   /**
-   * Get the underlying value as a {@link Message} type.
+   * Get the underlying value as a {@link MessageReflector} type.
    *
-   * @return The underlying {@link Message} value. null if the underlying value is not a {@link
-   *     Message} type.
+   * @return The underlying {@link MessageReflector} value. null if the underlying value is not a
+   *     {@link MessageReflector} type.
    */
   @Nullable
-  Message messageValue();
-
-  /**
-   * Get the underlying value and cast it to the class type.
-   *
-   * @param clazz The inferred class.
-   * @return The value casted to the inferred class type.
-   * @param <T> The class type.
-   */
-  <T> T value(Class<T> clazz);
+  MessageReflector messageValue();
 
   /**
    * Get the underlying value as a list.
@@ -57,4 +47,22 @@ public interface Value {
    *     list.
    */
   Map<Value, Value> mapValue();
+
+  /**
+   * Get the underlying value as it should be provided to CEL.
+   *
+   * @return The underlying value as a CEL-compatible type.
+   */
+  Object celValue();
+
+  /**
+   * Get the underlying value and cast it to the class type, which will be a type checkable
+   * internally by protovalidate-java.
+   *
+   * @param clazz The inferred class.
+   * @return The value cast to the inferred class type.
+   * @param <T> The class type.
+   */
+  @Nullable
+  <T> T jvmValue(Class<T> clazz);
 }

src/main/java/build/buf/protovalidate/internal/evaluator/AnyEvaluator.java

@@ -14,11 +14,12 @@
 
 package build.buf.protovalidate.internal.evaluator;
 
+import build.buf.protovalidate.MessageReflector;
 import build.buf.protovalidate.ValidationResult;
+import build.buf.protovalidate.Value;
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.Violation;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -45,12 +46,12 @@ class AnyEvaluator implements Evaluator {
 
   @Override
   public ValidationResult evaluate(Value val, boolean failFast) throws ExecutionException {
-    Message anyValue = val.messageValue();
+    MessageReflector anyValue = val.messageValue();
     if (anyValue == null) {
       return ValidationResult.EMPTY;
     }
     List<Violation> violationList = new ArrayList<>();
-    String typeURL = (String) anyValue.getField(typeURLDescriptor);
+    String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
     if (!in.isEmpty() && !in.contains(typeURL)) {
       Violation violation =
           Violation.newBuilder()

src/main/java/build/buf/protovalidate/internal/evaluator/EnumEvaluator.java

@@ -15,6 +15,7 @@
 package build.buf.protovalidate.internal.evaluator;
 
 import build.buf.protovalidate.ValidationResult;
+import build.buf.protovalidate.Value;
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.Violation;
 import com.google.protobuf.Descriptors;
@@ -62,11 +63,11 @@ public boolean tautology() {
    */
   @Override
   public ValidationResult evaluate(Value val, boolean failFast) throws ExecutionException {
-    Descriptors.EnumValueDescriptor enumValue = val.value(Descriptors.EnumValueDescriptor.class);
+    Integer enumValue = val.jvmValue(Integer.class);
     if (enumValue == null) {
       return ValidationResult.EMPTY;
     }
-    if (!values.contains(enumValue.getNumber())) {
+    if (!values.contains(enumValue)) {
       return new ValidationResult(
           Collections.singletonList(
               Violation.newBuilder()

src/main/java/build/buf/protovalidate/internal/evaluator/Evaluator.java

@@ -15,6 +15,7 @@
 package build.buf.protovalidate.internal.evaluator;
 
 import build.buf.protovalidate.ValidationResult;
+import build.buf.protovalidate.Value;
 import build.buf.protovalidate.exceptions.ExecutionException;
 
 /**

src/main/java/build/buf/protovalidate/internal/evaluator/FieldEvaluator.java

@@ -14,11 +14,12 @@
 
 package build.buf.protovalidate.internal.evaluator;
 
+import build.buf.protovalidate.MessageReflector;
 import build.buf.protovalidate.ValidationResult;
+import build.buf.protovalidate.Value;
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.Violation;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
@@ -68,13 +69,17 @@ public boolean tautology() {
 
   @Override
   public ValidationResult evaluate(Value val, boolean failFast) throws ExecutionException {
-    Message message = val.messageValue();
+    MessageReflector message = val.messageValue();
     if (message == null) {
       return ValidationResult.EMPTY;
     }
     boolean hasField;
     if (descriptor.isRepeated()) {
-      hasField = message.getRepeatedFieldCount(descriptor) != 0;
+      if (descriptor.isMapField()) {
+        hasField = !message.getField(descriptor).mapValue().isEmpty();
+      } else {
+        hasField = !message.getField(descriptor).repeatedValue().isEmpty();
+      }
     } else {
       hasField = message.hasField(descriptor);
     }
@@ -90,12 +95,11 @@ public ValidationResult evaluate(Value val, boolean failFast) throws ExecutionEx
     if (ignoreEmpty && !hasField) {
       return ValidationResult.EMPTY;
     }
-    Object fieldValue = message.getField(descriptor);
-    if (ignoreDefault && Objects.equals(zero, fieldValue)) {
+    Value fieldValue = message.getField(descriptor);
+    if (ignoreDefault && Objects.equals(zero, fieldValue.jvmValue(Object.class))) {
       return ValidationResult.EMPTY;
     }
-    ValidationResult evalResult =
-        valueEvaluator.evaluate(new ObjectValue(descriptor, fieldValue), failFast);
+    ValidationResult evalResult = valueEvaluator.evaluate(fieldValue, failFast);
     List<Violation> violations =
         ErrorPathUtils.prefixErrorPaths(evalResult.getViolations(), "%s", descriptor.getName());
     return new ValidationResult(violations);

src/main/java/build/buf/protovalidate/internal/evaluator/ObjectValue.java → src/main/java/build/buf/protovalidate/internal/evaluator/FieldValue.java

@@ -14,6 +14,8 @@
 
 package build.buf.protovalidate.internal.evaluator;
 
+import build.buf.protovalidate.MessageReflector;
+import build.buf.protovalidate.Value;
 import com.google.protobuf.AbstractMessage;
 import com.google.protobuf.Descriptors;
 import com.google.protobuf.Message;
@@ -25,11 +27,8 @@
 import javax.annotation.Nullable;
 import org.projectnessie.cel.common.ULong;
 
-/**
- * The {@link build.buf.protovalidate.internal.evaluator.Value} type that contains a field
- * descriptor and its value.
- */
-public final class ObjectValue implements Value {
+/** The {@link Value} type that contains a field descriptor and its value. */
+public final class FieldValue implements Value {
 
   /**
    * {@link com.google.protobuf.Descriptors.FieldDescriptor} is the field descriptor for the value.
@@ -40,27 +39,38 @@ public final class ObjectValue implements Value {
   private final Object value;
 
   /**
-   * Constructs a new {@link build.buf.protovalidate.internal.evaluator.ObjectValue}.
+   * Constructs a new {@link FieldValue}.
    *
    * @param fieldDescriptor The field descriptor for the value.
    * @param value The value associated with the field descriptor.
    */
-  ObjectValue(Descriptors.FieldDescriptor fieldDescriptor, Object value) {
+  FieldValue(Descriptors.FieldDescriptor fieldDescriptor, Object value) {
     this.fieldDescriptor = fieldDescriptor;
     this.value = value;
   }
 
-  @Nullable
   @Override
-  public Message messageValue() {
-    if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
-      return (Message) value;
+  @Nullable
+  public MessageReflector messageValue() {
+    if (fieldDescriptor.getType() == Descriptors.FieldDescriptor.Type.MESSAGE) {
+      return new ProtobufMessageReflector((Message) value);
     }
     return null;
   }
 
   @Override
-  public <T> T value(Class<T> clazz) {
+  public <T> T jvmValue(Class<T> clazz) {
+    if (value instanceof Descriptors.EnumValueDescriptor) {
+      return clazz.cast(((Descriptors.EnumValueDescriptor) value).getNumber());
+    }
+    return clazz.cast(value);
+  }
+
+  @Override
+  public Object celValue() {
+    if (value instanceof Descriptors.EnumValueDescriptor) {
+      return ((Descriptors.EnumValueDescriptor) value).getNumber();
+    }
     Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
     if (!fieldDescriptor.isRepeated()
         && (type == Descriptors.FieldDescriptor.Type.UINT32
@@ -74,9 +84,9 @@ public <T> T value(Class<T> clazz) {
        * When using uint32/uint64 in your protobuf objects or CEL expressions in Java,
        * wrap them with the org.projectnessie.cel.common.ULong type.
        */
-      return clazz.cast(ULong.valueOf(((Number) value).longValue()));
+      return ULong.valueOf(((Number) value).longValue());
     }
-    return clazz.cast(value);
+    return value;
   }
 
   @Override
@@ -85,7 +95,7 @@ public List<Value> repeatedValue() {
     if (fieldDescriptor.isRepeated()) {
       List<?> list = (List<?>) value;
       for (Object o : list) {
-        out.add(new build.buf.protovalidate.internal.evaluator.ObjectValue(fieldDescriptor, o));
+        out.add(new FieldValue(fieldDescriptor, o));
       }
     }
     return out;
@@ -103,12 +113,10 @@ public Map<Value, Value> mapValue() {
     Map<Value, Value> out = new HashMap<>(input.size());
     for (AbstractMessage entry : input) {
       Object keyValue = entry.getField(keyDesc);
-      Value keyJavaValue =
-          new build.buf.protovalidate.internal.evaluator.ObjectValue(keyDesc, keyValue);
+      Value keyJavaValue = new FieldValue(keyDesc, keyValue);
 
       Object valValue = entry.getField(valDesc);
-      Value valJavaValue =
-          new build.buf.protovalidate.internal.evaluator.ObjectValue(valDesc, valValue);
+      Value valJavaValue = new FieldValue(valDesc, valValue);
 
       out.put(keyJavaValue, valJavaValue);
     }

src/main/java/build/buf/protovalidate/internal/evaluator/ListEvaluator.java

@@ -15,6 +15,7 @@
 package build.buf.protovalidate.internal.evaluator;
 
 import build.buf.protovalidate.ValidationResult;
+import build.buf.protovalidate.Value;
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.Violation;
 import java.util.ArrayList;

src/main/java/build/buf/protovalidate/internal/evaluator/MapEvaluator.java

@@ -15,6 +15,7 @@
 package build.buf.protovalidate.internal.evaluator;
 
 import build.buf.protovalidate.ValidationResult;
+import build.buf.protovalidate.Value;
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldConstraints;
 import build.buf.validate.Violation;
@@ -100,7 +101,7 @@ private List<Violation> evalPairs(Value key, Value value, boolean failFast)
     violations.addAll(keyViolations);
     violations.addAll(valueViolations);
 
-    Object keyName = key.value(Object.class);
+    Object keyName = key.jvmValue(Object.class);
     if (keyName == null) {
       return Collections.emptyList();
     }

src/main/java/build/buf/protovalidate/internal/evaluator/MessageEvaluator.java

@@ -15,6 +15,7 @@
 package build.buf.protovalidate.internal.evaluator;
 
 import build.buf.protovalidate.ValidationResult;
+import build.buf.protovalidate.Value;
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.Violation;
 import java.util.ArrayList;