OneofEvaluator.java

// Copyright 2023-2025 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 build.buf.protovalidate.exceptions.ExecutionException;
import build.buf.validate.FieldPathElement;
import com.google.protobuf.Descriptors.OneofDescriptor;
import java.util.Collections;
import java.util.List;

/** {@link OneofEvaluator} performs validation on a oneof union. */
final class OneofEvaluator implements Evaluator {
  /** The {@link OneofDescriptor} targeted by this evaluator. */
  private final OneofDescriptor descriptor;

  /** Indicates that a member of the oneof must be set. */
  private final boolean required;

  /**
   * Constructs a {@link OneofEvaluator}.
   *
   * @param descriptor The targeted oneof descriptor.
   * @param required Indicates whether a member of the oneof must be set.
   */
  OneofEvaluator(OneofDescriptor descriptor, boolean required) {
    this.descriptor = descriptor;
    this.required = required;
  }

  @Override
  public boolean tautology() {
    return !required;
  }

  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
      throws ExecutionException {
    MessageReflector message = val.messageValue();
    if (message == null) {
        return RuleViolation.NO_VIOLATIONS;
    }
    boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
    if (!required || hasField) {
      return RuleViolation.NO_VIOLATIONS;
    }
    return Collections.singletonList(
        RuleViolation.newBuilder()
            .addFirstFieldPathElement(
                FieldPathElement.newBuilder().setFieldName(descriptor.getName()).build())
            .setRuleId("required")
            .setMessage("exactly one field is required in oneof"));
  }
}