Revert https://codereview.chromium.org/1291903002 (protobuf roll).

third_party/protobuf/java/src/main/java/com/google/protobuf/MessageReflection.java

Index: third_party/protobuf/java/src/main/java/com/google/protobuf/MessageReflection.java
diff --git a/third_party/protobuf/java/src/main/java/com/google/protobuf/MessageReflection.java b/third_party/protobuf/java/src/main/java/com/google/protobuf/MessageReflection.java
deleted file mode 100644
index de4bfd3ef3014d539b825c1d31e9668ac6703aad..0000000000000000000000000000000000000000
--- a/third_party/protobuf/java/src/main/java/com/google/protobuf/MessageReflection.java
+++ /dev/null
@@ -1,952 +0,0 @@
-// Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc.  All rights reserved.
-// https://developers.google.com/protocol-buffers/
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-package com.google.protobuf;
-
-import com.google.protobuf.Descriptors.FieldDescriptor;
-
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Map;
-import java.util.TreeMap;
-
-/**
- * Reflection utility methods shared by both mutable and immutable messages.
- *
- * @author liujisi@google.com (Pherl Liu)
- */
-class MessageReflection {
-
-  static void writeMessageTo(
-      Message message,
-      Map<FieldDescriptor, Object> fields,
-      CodedOutputStream output,
-      boolean alwaysWriteRequiredFields)
-      throws IOException {
-    final boolean isMessageSet =
-        message.getDescriptorForType().getOptions().getMessageSetWireFormat();
-    if (alwaysWriteRequiredFields) {
-      fields = new TreeMap<FieldDescriptor, Object>(fields);
-      for (final FieldDescriptor field :
-          message.getDescriptorForType().getFields()) {
-        if (field.isRequired() && !fields.containsKey(field)) {
-          fields.put(field, message.getField(field));
-        }
-      }
-    }
-    for (final Map.Entry<Descriptors.FieldDescriptor, Object> entry :
-        fields.entrySet()) {
-      final Descriptors.FieldDescriptor field = entry.getKey();
-      final Object value = entry.getValue();
-      if (isMessageSet && field.isExtension() &&
-          field.getType() == Descriptors.FieldDescriptor.Type.MESSAGE &&
-          !field.isRepeated()) {
-        output.writeMessageSetExtension(field.getNumber(), (Message) value);
-      } else {
-        FieldSet.writeField(field, value, output);
-      }
-    }
-
-    final UnknownFieldSet unknownFields = message.getUnknownFields();
-    if (isMessageSet) {
-      unknownFields.writeAsMessageSetTo(output);
-    } else {
-      unknownFields.writeTo(output);
-    }
-  }
-
-  static int getSerializedSize(
-      Message message,
-      Map<FieldDescriptor, Object> fields) {
-    int size = 0;
-    final boolean isMessageSet =
-        message.getDescriptorForType().getOptions().getMessageSetWireFormat();
-
-    for (final Map.Entry<Descriptors.FieldDescriptor, Object> entry :
-        fields.entrySet()) {
-      final Descriptors.FieldDescriptor field = entry.getKey();
-      final Object value = entry.getValue();
-      if (isMessageSet && field.isExtension() &&
-          field.getType() == Descriptors.FieldDescriptor.Type.MESSAGE &&
-          !field.isRepeated()) {
-        size += CodedOutputStream.computeMessageSetExtensionSize(
-            field.getNumber(), (Message) value);
-      } else {
-        size += FieldSet.computeFieldSize(field, value);
-      }
-    }
-
-    final UnknownFieldSet unknownFields = message.getUnknownFields();
-    if (isMessageSet) {
-      size += unknownFields.getSerializedSizeAsMessageSet();
-    } else {
-      size += unknownFields.getSerializedSize();
-    }
-    return size;
-  }
-
-  static String delimitWithCommas(List<String> parts) {
-    StringBuilder result = new StringBuilder();
-    for (String part : parts) {
-      if (result.length() > 0) {
-        result.append(", ");
-      }
-      result.append(part);
-    }
-    return result.toString();
-  }
-
-  @SuppressWarnings("unchecked")
-  static boolean isInitialized(MessageOrBuilder message) {
-    // Check that all required fields are present.
-    for (final Descriptors.FieldDescriptor field : message
-        .getDescriptorForType()
-        .getFields()) {
-      if (field.isRequired()) {
-        if (!message.hasField(field)) {
-          return false;
-        }
-      }
-    }
-
-    // Check that embedded messages are initialized.
-    for (final Map.Entry<Descriptors.FieldDescriptor, Object> entry :
-        message.getAllFields().entrySet()) {
-      final Descriptors.FieldDescriptor field = entry.getKey();
-      if (field.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
-        if (field.isRepeated()) {
-          for (final Message element
-              : (List<Message>) entry.getValue()) {
-            if (!element.isInitialized()) {
-              return false;
-            }
-          }
-        } else {
-          if (!((Message) entry.getValue()).isInitialized()) {
-            return false;
-          }
-        }
-      }
-    }
-
-    return true;
-  }
-
-  private static String subMessagePrefix(final String prefix,
-      final Descriptors.FieldDescriptor field,
-      final int index) {
-    final StringBuilder result = new StringBuilder(prefix);
-    if (field.isExtension()) {
-      result.append('(')
-          .append(field.getFullName())
-          .append(')');
-    } else {
-      result.append(field.getName());
-    }
-    if (index != -1) {
-      result.append('[')
-          .append(index)
-          .append(']');
-    }
-    result.append('.');
-    return result.toString();
-  }
-
-  private static void findMissingFields(final MessageOrBuilder message,
-      final String prefix,
-      final List<String> results) {
-    for (final Descriptors.FieldDescriptor field :
-        message.getDescriptorForType().getFields()) {
-      if (field.isRequired() && !message.hasField(field)) {
-        results.add(prefix + field.getName());
-      }
-    }
-
-    for (final Map.Entry<Descriptors.FieldDescriptor, Object> entry :
-        message.getAllFields().entrySet()) {
-      final Descriptors.FieldDescriptor field = entry.getKey();
-      final Object value = entry.getValue();
-
-      if (field.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
-        if (field.isRepeated()) {
-          int i = 0;
-          for (final Object element : (List) value) {
-            findMissingFields((MessageOrBuilder) element,
-                subMessagePrefix(prefix, field, i++),
-                results);
-          }
-        } else {
-          if (message.hasField(field)) {
-            findMissingFields((MessageOrBuilder) value,
-                subMessagePrefix(prefix, field, -1),
-                results);
-          }
-        }
-      }
-    }
-  }
-
-  /**
-   * Populates {@code this.missingFields} with the full "path" of each missing
-   * required field in the given message.
-   */
-  static List<String> findMissingFields(
-      final MessageOrBuilder message) {
-    final List<String> results = new ArrayList<String>();
-    findMissingFields(message, "", results);
-    return results;
-  }
-
-  static interface MergeTarget {
-    enum ContainerType {
-      MESSAGE, EXTENSION_SET
-    }
-
-    /**
-     * Returns the descriptor for the target.
-     */
-    public Descriptors.Descriptor getDescriptorForType();
-
-    public ContainerType getContainerType();
-
-    public ExtensionRegistry.ExtensionInfo findExtensionByName(
-        ExtensionRegistry registry, String name);
-
-    public ExtensionRegistry.ExtensionInfo findExtensionByNumber(
-        ExtensionRegistry registry, Descriptors.Descriptor containingType,
-        int fieldNumber);
-
-    /**
-     * Obtains the value of the given field, or the default value if it is not
-     * set.  For primitive fields, the boxed primitive value is returned. For
-     * enum fields, the EnumValueDescriptor for the value is returned. For
-     * embedded message fields, the sub-message is returned.  For repeated
-     * fields, a java.util.List is returned.
-     */
-    public Object getField(Descriptors.FieldDescriptor field);
-
-    /**
-     * Returns true if the given field is set.  This is exactly equivalent to
-     * calling the generated "has" accessor method corresponding to the field.
-     *
-     * @throws IllegalArgumentException The field is a repeated field, or {@code
-     *     field.getContainingType() != getDescriptorForType()}.
-     */
-    boolean hasField(Descriptors.FieldDescriptor field);
-
-    /**
-     * Sets a field to the given value.  The value must be of the correct type
-     * for this field, i.e. the same type that
-     * {@link Message#getField(Descriptors.FieldDescriptor)}
-     * would return.
-     */
-    MergeTarget setField(Descriptors.FieldDescriptor field, Object value);
-
-    /**
-     * Clears the field.  This is exactly equivalent to calling the generated
-     * "clear" accessor method corresponding to the field.
-     */
-    MergeTarget clearField(Descriptors.FieldDescriptor field);
-
-    /**
-     * Sets an element of a repeated field to the given value.  The value must
-     * be of the correct type for this field, i.e. the same type that {@link
-     * Message#getRepeatedField(Descriptors.FieldDescriptor, int)} would return.
-     *
-     * @throws IllegalArgumentException The field is not a repeated field, or
-     *                                  {@code field.getContainingType() !=
-     *                                  getDescriptorForType()}.
-     */
-    MergeTarget setRepeatedField(Descriptors.FieldDescriptor field,
-        int index, Object value);
-
-    /**
-     * Like {@code setRepeatedField}, but appends the value as a new element.
-     *
-     * @throws IllegalArgumentException The field is not a repeated field, or
-     *                                  {@code field.getContainingType() !=
-     *                                  getDescriptorForType()}.
-     */
-    MergeTarget addRepeatedField(Descriptors.FieldDescriptor field,
-        Object value);
-
-    /**
-     * Returns true if the given oneof is set.
-     *
-     * @throws IllegalArgumentException if
-     *           {@code oneof.getContainingType() != getDescriptorForType()}.
-     */
-    boolean hasOneof(Descriptors.OneofDescriptor oneof);
-
-    /**
-     * Clears the oneof.  This is exactly equivalent to calling the generated
-     * "clear" accessor method corresponding to the oneof.
-     */
-    MergeTarget clearOneof(Descriptors.OneofDescriptor oneof);
-
-    /**
-     * Obtains the FieldDescriptor if the given oneof is set. Returns null
-     * if no field is set.
-     */
-    Descriptors.FieldDescriptor getOneofFieldDescriptor(Descriptors.OneofDescriptor oneof);
-
-    /**
-     * Parse the input stream into a sub field group defined based on either
-     * FieldDescriptor or the default instance.
-     */
-    Object parseGroup(CodedInputStream input, ExtensionRegistryLite registry,
-        Descriptors.FieldDescriptor descriptor, Message defaultInstance)
-        throws IOException;
-
-    /**
-     * Parse the input stream into a sub field message defined based on either
-     * FieldDescriptor or the default instance.
-     */
-    Object parseMessage(CodedInputStream input, ExtensionRegistryLite registry,
-        Descriptors.FieldDescriptor descriptor, Message defaultInstance)
-        throws IOException;
-
-    /**
-     * Parse from a ByteString into a sub field message defined based on either
-     * FieldDescriptor or the default instance.  There isn't a varint indicating
-     * the length of the message at the beginning of the input ByteString.
-     */
-    Object parseMessageFromBytes(
-        ByteString bytes, ExtensionRegistryLite registry,
-        Descriptors.FieldDescriptor descriptor, Message defaultInstance)
-        throws IOException;
-
-    /**
-     * Returns the UTF8 validation level for the field.
-     */
-    WireFormat.Utf8Validation getUtf8Validation(Descriptors.FieldDescriptor
-        descriptor);
-
-    /**
-     * Returns a new merge target for a sub-field. When defaultInstance is
-     * provided, it indicates the descriptor is for an extension type, and
-     * implementations should create a new instance from the defaultInstance
-     * prototype directly.
-     */
-    MergeTarget newMergeTargetForField(
-        Descriptors.FieldDescriptor descriptor,
-        Message defaultInstance);
-
-    /**
-     * Finishes the merge and returns the underlying object.
-     */
-    Object finish();
-  }
-
-  static class BuilderAdapter implements MergeTarget {
-
-    private final Message.Builder builder;
-
-    public Descriptors.Descriptor getDescriptorForType() {
-      return builder.getDescriptorForType();
-    }
-
-    public BuilderAdapter(Message.Builder builder) {
-      this.builder = builder;
-    }
-
-    public Object getField(Descriptors.FieldDescriptor field) {
-      return builder.getField(field);
-    }
-
-    @Override
-    public boolean hasField(Descriptors.FieldDescriptor field) {
-      return builder.hasField(field);
-    }
-
-    public MergeTarget setField(Descriptors.FieldDescriptor field,
-        Object value) {
-      builder.setField(field, value);
-      return this;
-    }
-
-    public MergeTarget clearField(Descriptors.FieldDescriptor field) {
-      builder.clearField(field);
-      return this;
-    }
-
-    public MergeTarget setRepeatedField(
-        Descriptors.FieldDescriptor field, int index, Object value) {
-      builder.setRepeatedField(field, index, value);
-      return this;
-    }
-
-    public MergeTarget addRepeatedField(
-        Descriptors.FieldDescriptor field, Object value) {
-      builder.addRepeatedField(field, value);
-      return this;
-    }
-
-    @Override
-    public boolean hasOneof(Descriptors.OneofDescriptor oneof) {
-      return builder.hasOneof(oneof);
-    }
-
-    @Override
-    public MergeTarget clearOneof(Descriptors.OneofDescriptor oneof) {
-      builder.clearOneof(oneof);
-      return this;
-    }
-
-    @Override
-    public Descriptors.FieldDescriptor getOneofFieldDescriptor(Descriptors.OneofDescriptor oneof) {
-      return builder.getOneofFieldDescriptor(oneof);
-    }
-
-    public ContainerType getContainerType() {
-      return ContainerType.MESSAGE;
-    }
-
-    public ExtensionRegistry.ExtensionInfo findExtensionByName(
-        ExtensionRegistry registry, String name) {
-      return registry.findImmutableExtensionByName(name);
-    }
-
-    public ExtensionRegistry.ExtensionInfo findExtensionByNumber(
-        ExtensionRegistry registry, Descriptors.Descriptor containingType,
-        int fieldNumber) {
-      return registry.findImmutableExtensionByNumber(containingType,
-          fieldNumber);
-    }
-
-    public Object parseGroup(CodedInputStream input,
-        ExtensionRegistryLite extensionRegistry,
-        Descriptors.FieldDescriptor field, Message defaultInstance)
-        throws IOException {
-      Message.Builder subBuilder;
-      // When default instance is not null. The field is an extension field.
-      if (defaultInstance != null) {
-        subBuilder = defaultInstance.newBuilderForType();
-      } else {
-        subBuilder = builder.newBuilderForField(field);
-      }
-      if (!field.isRepeated()) {
-        Message originalMessage = (Message) getField(field);
-        if (originalMessage != null) {
-          subBuilder.mergeFrom(originalMessage);
-        }
-      }
-      input.readGroup(field.getNumber(), subBuilder, extensionRegistry);
-      return subBuilder.buildPartial();
-    }
-
-    public Object parseMessage(CodedInputStream input,
-        ExtensionRegistryLite extensionRegistry,
-        Descriptors.FieldDescriptor field, Message defaultInstance)
-        throws IOException {
-      Message.Builder subBuilder;
-      // When default instance is not null. The field is an extension field.
-      if (defaultInstance != null) {
-        subBuilder = defaultInstance.newBuilderForType();
-      } else {
-        subBuilder = builder.newBuilderForField(field);
-      }
-      if (!field.isRepeated()) {
-        Message originalMessage = (Message) getField(field);
-        if (originalMessage != null) {
-          subBuilder.mergeFrom(originalMessage);
-        }
-      }
-      input.readMessage(subBuilder, extensionRegistry);
-      return subBuilder.buildPartial();
-    }
-
-    public Object parseMessageFromBytes(ByteString bytes,
-        ExtensionRegistryLite extensionRegistry,
-        Descriptors.FieldDescriptor field, Message defaultInstance)
-        throws IOException {
-      Message.Builder subBuilder;
-      // When default instance is not null. The field is an extension field.
-      if (defaultInstance != null) {
-        subBuilder = defaultInstance.newBuilderForType();
-      } else {
-        subBuilder = builder.newBuilderForField(field);
-      }
-      if (!field.isRepeated()) {
-        Message originalMessage = (Message) getField(field);
-        if (originalMessage != null) {
-          subBuilder.mergeFrom(originalMessage);
-        }
-      }
-      subBuilder.mergeFrom(bytes, extensionRegistry);
-      return subBuilder.buildPartial();
-    }
-
-    public MergeTarget newMergeTargetForField(Descriptors.FieldDescriptor field,
-        Message defaultInstance) {
-      if (defaultInstance != null) {
-        return new BuilderAdapter(
-            defaultInstance.newBuilderForType());
-      } else {
-        return new BuilderAdapter(builder.newBuilderForField(field));
-      }
-    }
-
-    public WireFormat.Utf8Validation
-        getUtf8Validation(Descriptors.FieldDescriptor descriptor) {
-      if (descriptor.needsUtf8Check()) {
-        return WireFormat.Utf8Validation.STRICT;
-      }
-      // TODO(liujisi): support lazy strings for repeated fields.
-      if (!descriptor.isRepeated()
-          && builder instanceof GeneratedMessage.Builder) {
-        return WireFormat.Utf8Validation.LAZY;
-      }
-      return WireFormat.Utf8Validation.LOOSE;
-    }
-
-    public Object finish() {
-      return builder.buildPartial();
-    }
-  }
-
-
-  static class ExtensionAdapter implements MergeTarget {
-
-    private final FieldSet<Descriptors.FieldDescriptor> extensions;
-
-    ExtensionAdapter(FieldSet<Descriptors.FieldDescriptor> extensions) {
-      this.extensions = extensions;
-    }
-
-    public Descriptors.Descriptor getDescriptorForType() {
-      throw new UnsupportedOperationException(
-          "getDescriptorForType() called on FieldSet object");
-    }
-
-    public Object getField(Descriptors.FieldDescriptor field) {
-      return extensions.getField(field);
-    }
-
-    public boolean hasField(Descriptors.FieldDescriptor field) {
-      return extensions.hasField(field);
-    }
-
-    public MergeTarget setField(Descriptors.FieldDescriptor field,
-        Object value) {
-      extensions.setField(field, value);
-      return this;
-    }
-
-    public MergeTarget clearField(Descriptors.FieldDescriptor field) {
-      extensions.clearField(field);
-      return this;
-    }
-
-    public MergeTarget setRepeatedField(
-        Descriptors.FieldDescriptor field, int index, Object value) {
-      extensions.setRepeatedField(field, index, value);
-      return this;
-    }
-
-    public MergeTarget addRepeatedField(
-        Descriptors.FieldDescriptor field, Object value) {
-      extensions.addRepeatedField(field, value);
-      return this;
-    }
-
-    @Override
-    public boolean hasOneof(Descriptors.OneofDescriptor oneof) {
-      return false;
-    }
-
-    @Override
-    public MergeTarget clearOneof(Descriptors.OneofDescriptor oneof) {
-      // Nothing to clear.
-      return this;
-    }
-
-    @Override
-    public Descriptors.FieldDescriptor getOneofFieldDescriptor(Descriptors.OneofDescriptor oneof) {
-      return null;
-    }
-
-    public ContainerType getContainerType() {
-      return ContainerType.EXTENSION_SET;
-    }
-
-    public ExtensionRegistry.ExtensionInfo findExtensionByName(
-        ExtensionRegistry registry, String name) {
-      return registry.findImmutableExtensionByName(name);
-    }
-
-    public ExtensionRegistry.ExtensionInfo findExtensionByNumber(
-        ExtensionRegistry registry, Descriptors.Descriptor containingType,
-        int fieldNumber) {
-      return registry.findImmutableExtensionByNumber(containingType,
-          fieldNumber);
-    }
-
-    public Object parseGroup(CodedInputStream input,
-        ExtensionRegistryLite registry, Descriptors.FieldDescriptor field,
-        Message defaultInstance) throws IOException {
-      Message.Builder subBuilder =
-          defaultInstance.newBuilderForType();
-      if (!field.isRepeated()) {
-        Message originalMessage = (Message) getField(field);
-        if (originalMessage != null) {
-          subBuilder.mergeFrom(originalMessage);
-        }
-      }
-      input.readGroup(field.getNumber(), subBuilder, registry);
-      return subBuilder.buildPartial();
-    }
-
-    public Object parseMessage(CodedInputStream input,
-        ExtensionRegistryLite registry, Descriptors.FieldDescriptor field,
-        Message defaultInstance) throws IOException {
-      Message.Builder subBuilder =
-          defaultInstance.newBuilderForType();
-      if (!field.isRepeated()) {
-        Message originalMessage = (Message) getField(field);
-        if (originalMessage != null) {
-          subBuilder.mergeFrom(originalMessage);
-        }
-      }
-      input.readMessage(subBuilder, registry);
-      return subBuilder.buildPartial();
-    }
-
-    public Object parseMessageFromBytes(ByteString bytes,
-        ExtensionRegistryLite registry, Descriptors.FieldDescriptor field,
-        Message defaultInstance) throws IOException {
-      Message.Builder subBuilder =  defaultInstance.newBuilderForType();
-      if (!field.isRepeated()) {
-        Message originalMessage = (Message) getField(field);
-        if (originalMessage != null) {
-          subBuilder.mergeFrom(originalMessage);
-        }
-      }
-      subBuilder.mergeFrom(bytes, registry);
-      return subBuilder.buildPartial();
-    }
-
-    public MergeTarget newMergeTargetForField(
-        Descriptors.FieldDescriptor descriptor, Message defaultInstance) {
-      throw new UnsupportedOperationException(
-          "newMergeTargetForField() called on FieldSet object");
-    }
-
-    public WireFormat.Utf8Validation
-        getUtf8Validation(Descriptors.FieldDescriptor descriptor) {
-      if (descriptor.needsUtf8Check()) {
-        return WireFormat.Utf8Validation.STRICT;
-      }
-      // TODO(liujisi): support lazy strings for ExtesnsionSet.
-      return WireFormat.Utf8Validation.LOOSE;
-    }
-
-    public Object finish() {
-      throw new UnsupportedOperationException(
-          "finish() called on FieldSet object");
-    }
-  }
-
-  /**
-   * Parses a single field into MergeTarget. The target can be Message.Builder,
-   * FieldSet or MutableMessage.
-   *
-   * Package-private because it is used by GeneratedMessage.ExtendableMessage.
-   *
-   * @param tag The tag, which should have already been read.
-   * @return {@code true} unless the tag is an end-group tag.
-   */
-  static boolean mergeFieldFrom(
-      CodedInputStream input,
-      UnknownFieldSet.Builder unknownFields,
-      ExtensionRegistryLite extensionRegistry,
-      Descriptors.Descriptor type,
-      MergeTarget target,
-      int tag) throws IOException {
-    if (type.getOptions().getMessageSetWireFormat() &&
-        tag == WireFormat.MESSAGE_SET_ITEM_TAG) {
-      mergeMessageSetExtensionFromCodedStream(
-          input, unknownFields, extensionRegistry, type, target);
-      return true;
-    }
-
-    final int wireType = WireFormat.getTagWireType(tag);
-    final int fieldNumber = WireFormat.getTagFieldNumber(tag);
-
-    final Descriptors.FieldDescriptor field;
-    Message defaultInstance = null;
-
-    if (type.isExtensionNumber(fieldNumber)) {
-      // extensionRegistry may be either ExtensionRegistry or
-      // ExtensionRegistryLite.  Since the type we are parsing is a full
-      // message, only a full ExtensionRegistry could possibly contain
-      // extensions of it.  Otherwise we will treat the registry as if it
-      // were empty.
-      if (extensionRegistry instanceof ExtensionRegistry) {
-        final ExtensionRegistry.ExtensionInfo extension =
-            target.findExtensionByNumber((ExtensionRegistry) extensionRegistry,
-                type, fieldNumber);
-        if (extension == null) {
-          field = null;
-        } else {
-          field = extension.descriptor;
-          defaultInstance = extension.defaultInstance;
-          if (defaultInstance == null &&
-              field.getJavaType()
-                  == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
-            throw new IllegalStateException(
-                "Message-typed extension lacked default instance: " +
-                    field.getFullName());
-          }
-        }
-      } else {
-        field = null;
-      }
-    } else if (target.getContainerType() == MergeTarget.ContainerType.MESSAGE) {
-      field = type.findFieldByNumber(fieldNumber);
-    } else {
-      field = null;
-    }
-
-    boolean unknown = false;
-    boolean packed = false;
-    if (field == null) {
-      unknown = true;  // Unknown field.
-    } else if (wireType == FieldSet.getWireFormatForFieldType(
-        field.getLiteType(),
-        false  /* isPacked */)) {
-      packed = false;
-    } else if (field.isPackable() &&
-        wireType == FieldSet.getWireFormatForFieldType(
-            field.getLiteType(),
-            true  /* isPacked */)) {
-      packed = true;
-    } else {
-      unknown = true;  // Unknown wire type.
-    }
-
-    if (unknown) {  // Unknown field or wrong wire type.  Skip.
-      return unknownFields.mergeFieldFrom(tag, input);
-    }
-
-    if (packed) {
-      final int length = input.readRawVarint32();
-      final int limit = input.pushLimit(length);
-      if (field.getLiteType() == WireFormat.FieldType.ENUM) {
-        while (input.getBytesUntilLimit() > 0) {
-          final int rawValue = input.readEnum();
-          if (field.getFile().supportsUnknownEnumValue()) {
-            target.addRepeatedField(field,
-                field.getEnumType().findValueByNumberCreatingIfUnknown(rawValue));
-          } else {
-            final Object value = field.getEnumType().findValueByNumber(rawValue);
-            if (value == null) {
-              // If the number isn't recognized as a valid value for this
-              // enum, drop it (don't even add it to unknownFields).
-              return true;
-            }
-            target.addRepeatedField(field, value);
-          }
-        }
-      } else {
-        while (input.getBytesUntilLimit() > 0) {
-          final Object value = WireFormat.readPrimitiveField(
-              input, field.getLiteType(), target.getUtf8Validation(field));
-          target.addRepeatedField(field, value);
-        }
-      }
-      input.popLimit(limit);
-    } else {
-      final Object value;
-      switch (field.getType()) {
-        case GROUP: {
-          value = target
-              .parseGroup(input, extensionRegistry, field, defaultInstance);
-          break;
-        }
-        case MESSAGE: {
-          value = target
-              .parseMessage(input, extensionRegistry, field, defaultInstance);
-          break;
-        }
-        case ENUM:
-          final int rawValue = input.readEnum();
-          if (field.getFile().supportsUnknownEnumValue()) {
-            value = field.getEnumType().findValueByNumberCreatingIfUnknown(rawValue);
-          } else {
-            value = field.getEnumType().findValueByNumber(rawValue);
-            // If the number isn't recognized as a valid value for this enum,
-            // drop it.
-            if (value == null) {
-              unknownFields.mergeVarintField(fieldNumber, rawValue);
-              return true;
-            }
-          }
-          break;
-        default:
-          value = WireFormat.readPrimitiveField(
-              input, field.getLiteType(), target.getUtf8Validation(field));
-          break;
-      }
-
-      if (field.isRepeated()) {
-        target.addRepeatedField(field, value);
-      } else {
-        target.setField(field, value);
-      }
-    }
-
-    return true;
-  }
-
-  /**
-   * Called by {@code #mergeFieldFrom()} to parse a MessageSet extension into
-   * MergeTarget.
-   */
-  private static void mergeMessageSetExtensionFromCodedStream(
-      CodedInputStream input,
-      UnknownFieldSet.Builder unknownFields,
-      ExtensionRegistryLite extensionRegistry,
-      Descriptors.Descriptor type,
-      MergeTarget target) throws IOException {
-
-    // The wire format for MessageSet is:
-    //   message MessageSet {
-    //     repeated group Item = 1 {
-    //       required int32 typeId = 2;
-    //       required bytes message = 3;
-    //     }
-    //   }
-    // "typeId" is the extension's field number.  The extension can only be
-    // a message type, where "message" contains the encoded bytes of that
-    // message.
-    //
-    // In practice, we will probably never see a MessageSet item in which
-    // the message appears before the type ID, or where either field does not
-    // appear exactly once.  However, in theory such cases are valid, so we
-    // should be prepared to accept them.
-
-    int typeId = 0;
-    ByteString rawBytes = null; // If we encounter "message" before "typeId"
-    ExtensionRegistry.ExtensionInfo extension = null;
-
-    // Read bytes from input, if we get it's type first then parse it eagerly,
-    // otherwise we store the raw bytes in a local variable.
-    while (true) {
-      final int tag = input.readTag();
-      if (tag == 0) {
-        break;
-      }
-
-      if (tag == WireFormat.MESSAGE_SET_TYPE_ID_TAG) {
-        typeId = input.readUInt32();
-        if (typeId != 0) {
-          // extensionRegistry may be either ExtensionRegistry or
-          // ExtensionRegistryLite. Since the type we are parsing is a full
-          // message, only a full ExtensionRegistry could possibly contain
-          // extensions of it. Otherwise we will treat the registry as if it
-          // were empty.
-          if (extensionRegistry instanceof ExtensionRegistry) {
-            extension = target.findExtensionByNumber(
-                (ExtensionRegistry) extensionRegistry, type, typeId);
-          }
-        }
-
-      } else if (tag == WireFormat.MESSAGE_SET_MESSAGE_TAG) {
-        if (typeId != 0) {
-          if (extension != null &&
-              ExtensionRegistryLite.isEagerlyParseMessageSets()) {
-            // We already know the type, so we can parse directly from the
-            // input with no copying.  Hooray!
-            eagerlyMergeMessageSetExtension(
-                input, extension, extensionRegistry, target);
-            rawBytes = null;
-            continue;
-          }
-        }
-        // We haven't seen a type ID yet or we want parse message lazily.
-        rawBytes = input.readBytes();
-
-      } else { // Unknown tag. Skip it.
-        if (!input.skipField(tag)) {
-          break; // End of group
-        }
-      }
-    }
-    input.checkLastTagWas(WireFormat.MESSAGE_SET_ITEM_END_TAG);
-
-    // Process the raw bytes.
-    if (rawBytes != null && typeId != 0) { // Zero is not a valid type ID.
-      if (extension != null) { // We known the type
-        mergeMessageSetExtensionFromBytes(
-            rawBytes, extension, extensionRegistry, target);
-      } else { // We don't know how to parse this. Ignore it.
-        if (rawBytes != null) {
-          unknownFields.mergeField(typeId, UnknownFieldSet.Field.newBuilder()
-              .addLengthDelimited(rawBytes).build());
-        }
-      }
-    }
-  }
-
-  private static void mergeMessageSetExtensionFromBytes(
-      ByteString rawBytes,
-      ExtensionRegistry.ExtensionInfo extension,
-      ExtensionRegistryLite extensionRegistry,
-      MergeTarget target) throws IOException {
-
-    Descriptors.FieldDescriptor field = extension.descriptor;
-    boolean hasOriginalValue = target.hasField(field);
-
-    if (hasOriginalValue || ExtensionRegistryLite.isEagerlyParseMessageSets()) {
-      // If the field already exists, we just parse the field.
-      Object value = target.parseMessageFromBytes(
-          rawBytes, extensionRegistry,field, extension.defaultInstance);
-      target.setField(field, value);
-    } else {
-      // Use LazyField to load MessageSet lazily.
-      LazyField lazyField = new LazyField(
-          extension.defaultInstance, extensionRegistry, rawBytes);
-      target.setField(field, lazyField);
-    }
-  }
-
-  private static void eagerlyMergeMessageSetExtension(
-      CodedInputStream input,
-      ExtensionRegistry.ExtensionInfo extension,
-      ExtensionRegistryLite extensionRegistry,
-      MergeTarget target) throws IOException {
-    Descriptors.FieldDescriptor field = extension.descriptor;
-    Object value = target.parseMessage(input, extensionRegistry, field,
-                                       extension.defaultInstance);
-    target.setField(field, value);
-  }
-}