protobuf/python/google/protobuf/json_format.py

# Protocol Buffers - Google's data interchange format
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"""Contains routines for printing protocol messages in JSON format.

Simple usage example:

  # Create a proto object and serialize it to a json format string.
  message = my_proto_pb2.MyMessage(foo='bar')
  json_string = json_format.MessageToJson(message)

  # Parse a json format string to proto object.
  message = json_format.Parse(json_string, my_proto_pb2.MyMessage())
"""

__author__ = 'jieluo@google.com (Jie Luo)'

import base64
import json
import math
from six import text_type
import sys

from google.protobuf import descriptor

_TIMESTAMPFOMAT = '%Y-%m-%dT%H:%M:%S'
_INT_TYPES = frozenset([descriptor.FieldDescriptor.CPPTYPE_INT32,
                        descriptor.FieldDescriptor.CPPTYPE_UINT32,
                        descriptor.FieldDescriptor.CPPTYPE_INT64,
                        descriptor.FieldDescriptor.CPPTYPE_UINT64])
_INT64_TYPES = frozenset([descriptor.FieldDescriptor.CPPTYPE_INT64,
                          descriptor.FieldDescriptor.CPPTYPE_UINT64])
_FLOAT_TYPES = frozenset([descriptor.FieldDescriptor.CPPTYPE_FLOAT,
                          descriptor.FieldDescriptor.CPPTYPE_DOUBLE])
_INFINITY = 'Infinity'
_NEG_INFINITY = '-Infinity'
_NAN = 'NaN'


class Error(Exception):
  """Top-level module error for json_format."""


class SerializeToJsonError(Error):
  """Thrown if serialization to JSON fails."""


class ParseError(Error):
  """Thrown in case of parsing error."""


def MessageToJson(message, including_default_value_fields=False):
  """Converts protobuf message to JSON format.

  Args:
    message: The protocol buffers message instance to serialize.
    including_default_value_fields: If True, singular primitive fields,
        repeated fields, and map fields will always be serialized.  If
        False, only serialize non-empty fields.  Singular message fields
        and oneof fields are not affected by this option.

  Returns:
    A string containing the JSON formatted protocol buffer message.
  """
  js = _MessageToJsonObject(message, including_default_value_fields)
  return json.dumps(js, indent=2)


def _MessageToJsonObject(message, including_default_value_fields):
  """Converts message to an object according to Proto3 JSON Specification."""
  message_descriptor = message.DESCRIPTOR
  if hasattr(message, 'ToJsonString'):
    return message.ToJsonString()
  if _IsWrapperMessage(message_descriptor):
    return _WrapperMessageToJsonObject(message)
  return _RegularMessageToJsonObject(message, including_default_value_fields)


def _IsMapEntry(field):
  return (field.type == descriptor.FieldDescriptor.TYPE_MESSAGE and
          field.message_type.has_options and
          field.message_type.GetOptions().map_entry)


def _RegularMessageToJsonObject(message, including_default_value_fields):
  """Converts normal message according to Proto3 JSON Specification."""
  js = {}
  fields = message.ListFields()
  include_default = including_default_value_fields

  try:
    for field, value in fields:
      name = field.camelcase_name
      if _IsMapEntry(field):
        # Convert a map field.
        v_field = field.message_type.fields_by_name['value']
        js_map = {}
        for key in value:
          if isinstance(key, bool):
            if key:
              recorded_key = 'true'
            else:
              recorded_key = 'false'
          else:
            recorded_key = key
          js_map[recorded_key] = _FieldToJsonObject(
              v_field, value[key], including_default_value_fields)
        js[name] = js_map
      elif field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
        # Convert a repeated field.
        js[name] = [_FieldToJsonObject(field, k, include_default)
                    for k in value]
      else:
        js[name] = _FieldToJsonObject(field, value, include_default)

    # Serialize default value if including_default_value_fields is True.
    if including_default_value_fields:
      message_descriptor = message.DESCRIPTOR
      for field in message_descriptor.fields:
        # Singular message fields and oneof fields will not be affected.
        if ((field.label != descriptor.FieldDescriptor.LABEL_REPEATED and
             field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE) or
            field.containing_oneof):
          continue
        name = field.camelcase_name
        if name in js:
          # Skip the field which has been serailized already.
          continue
        if _IsMapEntry(field):
          js[name] = {}
        elif field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
          js[name] = []
        else:
          js[name] = _FieldToJsonObject(field, field.default_value)

  except ValueError as e:
    raise SerializeToJsonError(
        'Failed to serialize {0} field: {1}.'.format(field.name, e))

  return js


def _FieldToJsonObject(
    field, value, including_default_value_fields=False):
  """Converts field value according to Proto3 JSON Specification."""
  if field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
    return _MessageToJsonObject(value, including_default_value_fields)
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_ENUM:
    enum_value = field.enum_type.values_by_number.get(value, None)
    if enum_value is not None:
      return enum_value.name
    else:
      raise SerializeToJsonError('Enum field contains an integer value '
                                 'which can not mapped to an enum value.')
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_STRING:
    if field.type == descriptor.FieldDescriptor.TYPE_BYTES:
      # Use base64 Data encoding for bytes
      return base64.b64encode(value).decode('utf-8')
    else:
      return value
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_BOOL:
    return bool(value)
  elif field.cpp_type in _INT64_TYPES:
    return str(value)
  elif field.cpp_type in _FLOAT_TYPES:
    if math.isinf(value):
      if value < 0.0:
        return _NEG_INFINITY
      else:
        return _INFINITY
    if math.isnan(value):
      return _NAN
  return value


def _IsWrapperMessage(message_descriptor):
  return message_descriptor.file.name == 'google/protobuf/wrappers.proto'


def _WrapperMessageToJsonObject(message):
  return _FieldToJsonObject(
      message.DESCRIPTOR.fields_by_name['value'], message.value)


def _DuplicateChecker(js):
  result = {}
  for name, value in js:
    if name in result:
      raise ParseError('Failed to load JSON: duplicate key {0}.'.format(name))
    result[name] = value
  return result


def Parse(text, message):
  """Parses a JSON representation of a protocol message into a message.

  Args:
    text: Message JSON representation.
    message: A protocol beffer message to merge into.

  Returns:
    The same message passed as argument.

  Raises::
    ParseError: On JSON parsing problems.
  """
  if not isinstance(text, text_type): text = text.decode('utf-8')
  try:
    if sys.version_info < (2, 7):
      # object_pair_hook is not supported before python2.7
      js = json.loads(text)
    else:
      js = json.loads(text, object_pairs_hook=_DuplicateChecker)
  except ValueError as e:
    raise ParseError('Failed to load JSON: {0}.'.format(str(e)))
  _ConvertFieldValuePair(js, message)
  return message


def _ConvertFieldValuePair(js, message):
  """Convert field value pairs into regular message.

  Args:
    js: A JSON object to convert the field value pairs.
    message: A regular protocol message to record the data.

  Raises:
    ParseError: In case of problems converting.
  """
  names = []
  message_descriptor = message.DESCRIPTOR
  for name in js:
    try:
      field = message_descriptor.fields_by_camelcase_name.get(name, None)
      if not field:
        raise ParseError(
            'Message type "{0}" has no field named "{1}".'.format(
                message_descriptor.full_name, name))
      if name in names:
        raise ParseError(
            'Message type "{0}" should not have multiple "{1}" fields.'.format(
                message.DESCRIPTOR.full_name, name))
      names.append(name)
      # Check no other oneof field is parsed.
      if field.containing_oneof is not None:
        oneof_name = field.containing_oneof.name
        if oneof_name in names:
          raise ParseError('Message type "{0}" should not have multiple "{1}" '
                           'oneof fields.'.format(
                               message.DESCRIPTOR.full_name, oneof_name))
        names.append(oneof_name)

      value = js[name]
      if value is None:
        message.ClearField(field.name)
        continue

      # Parse field value.
      if _IsMapEntry(field):
        message.ClearField(field.name)
        _ConvertMapFieldValue(value, message, field)
      elif field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
        message.ClearField(field.name)
        if not isinstance(value, list):
          raise ParseError('repeated field {0} must be in [] which is '
                           '{1}.'.format(name, value))
        for item in value:
          if item is None:
            continue
          if field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
            sub_message = getattr(message, field.name).add()
            _ConvertMessage(item, sub_message)
          else:
            getattr(message, field.name).append(
                _ConvertScalarFieldValue(item, field))
      elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
        sub_message = getattr(message, field.name)
        _ConvertMessage(value, sub_message)
      else:
        setattr(message, field.name, _ConvertScalarFieldValue(value, field))
    except ParseError as e:
      if field and field.containing_oneof is None:
        raise ParseError('Failed to parse {0} field: {1}'.format(name, e))
      else:
        raise ParseError(str(e))
    except ValueError as e:
      raise ParseError('Failed to parse {0} field: {1}.'.format(name, e))
    except TypeError as e:
      raise ParseError('Failed to parse {0} field: {1}.'.format(name, e))


def _ConvertMessage(value, message):
  """Convert a JSON object into a message.

  Args:
    value: A JSON object.
    message: A WKT or regular protocol message to record the data.

  Raises:
    ParseError: In case of convert problems.
  """
  message_descriptor = message.DESCRIPTOR
  if hasattr(message, 'FromJsonString'):
    message.FromJsonString(value)
  elif _IsWrapperMessage(message_descriptor):
    _ConvertWrapperMessage(value, message)
  else:
    _ConvertFieldValuePair(value, message)

def _ConvertWrapperMessage(value, message):
  """Convert a JSON representation into Wrapper message."""
  field = message.DESCRIPTOR.fields_by_name['value']
  setattr(message, 'value', _ConvertScalarFieldValue(value, field))


def _ConvertMapFieldValue(value, message, field):
  """Convert map field value for a message map field.

  Args:
    value: A JSON object to convert the map field value.
    message: A protocol message to record the converted data.
    field: The descriptor of the map field to be converted.

  Raises:
    ParseError: In case of convert problems.
  """
  if not isinstance(value, dict):
    raise ParseError(
        'Map fieled {0} must be in {} which is {1}.'.format(field.name, value))
  key_field = field.message_type.fields_by_name['key']
  value_field = field.message_type.fields_by_name['value']
  for key in value:
    key_value = _ConvertScalarFieldValue(key, key_field, True)
    if value_field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
      _ConvertMessage(value[key], getattr(message, field.name)[key_value])
    else:
      getattr(message, field.name)[key_value] = _ConvertScalarFieldValue(
          value[key], value_field)


def _ConvertScalarFieldValue(value, field, require_str=False):
  """Convert a single scalar field value.

  Args:
    value: A scalar value to convert the scalar field value.
    field: The descriptor of the field to convert.
    require_str: If True, the field value must be a str.

  Returns:
    The converted scalar field value

  Raises:
    ParseError: In case of convert problems.
  """
  if field.cpp_type in _INT_TYPES:
    return _ConvertInteger(value)
  elif field.cpp_type in _FLOAT_TYPES:
    return _ConvertFloat(value)
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_BOOL:
    return _ConvertBool(value, require_str)
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_STRING:
    if field.type == descriptor.FieldDescriptor.TYPE_BYTES:
      return base64.b64decode(value)
    else:
      return value
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_ENUM:
    # Convert an enum value.
    enum_value = field.enum_type.values_by_name.get(value, None)
    if enum_value is None:
      raise ParseError(
          'Enum value must be a string literal with double quotes. '
          'Type "{0}" has no value named {1}.'.format(
              field.enum_type.full_name, value))
    return enum_value.number


def _ConvertInteger(value):
  """Convert an integer.

  Args:
    value: A scalar value to convert.

  Returns:
    The integer value.

  Raises:
    ParseError: If an integer couldn't be consumed.
  """
  if isinstance(value, float):
    raise ParseError('Couldn\'t parse integer: {0}.'.format(value))

  if isinstance(value, text_type) and value.find(' ') != -1:
    raise ParseError('Couldn\'t parse integer: "{0}".'.format(value))

  return int(value)


def _ConvertFloat(value):
  """Convert an floating point number."""
  if value == 'nan':
    raise ParseError('Couldn\'t parse float "nan", use "NaN" instead.')
  try:
    # Assume Python compatible syntax.
    return float(value)
  except ValueError:
    # Check alternative spellings.
    if value == _NEG_INFINITY:
      return float('-inf')
    elif value == _INFINITY:
      return float('inf')
    elif value == _NAN:
      return float('nan')
    else:
      raise ParseError('Couldn\'t parse float: {0}.'.format(value))


def _ConvertBool(value, require_str):
  """Convert a boolean value.

  Args:
    value: A scalar value to convert.
    require_str: If True, value must be a str.

  Returns:
    The bool parsed.

  Raises:
    ParseError: If a boolean value couldn't be consumed.
  """
  if require_str:
    if value == 'true':
      return True
    elif value == 'false':
      return False
    else:
      raise ParseError('Expected "true" or "false", not {0}.'.format(value))

  if not isinstance(value, bool):
    raise ParseError('Expected true or false without quotes.')
  return value