api/validate.py

# -*- coding: utf-8 -*-
# Copyright 2019 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Validation helpers for simple input validation in the API."""

from __future__ import print_function

import os

from chromite.lib import cros_build_lib
from chromite.lib import cros_logging as logging

from google.protobuf import message as protobuf_message


def _value(field, message):
  """Helper function to fetch the value of the field.

  Args:
    field (str): The field name. Can be nested via . separation.
    message (Message): The protobuf message it is being fetched from.

  Returns:
    str|None|int|list|Message|bool - The value of the field.
  """
  value = message
  for part in field.split('.'):
    if not isinstance(value, protobuf_message.Message):
      value = None
      break

    try:
      value = getattr(value, part)
    except AttributeError as e:
      cros_build_lib.Die('Invalid field: %s', e.message)

  return value


#pylint: disable=docstring-misnamed-args
def exists(*fields):
  """Validate that the paths in |fields| exist.

  Args:
    fields (str): The fields being checked. Can be . separated nested
      fields.
  """
  assert fields

  def decorator(func):
    def _exists(input_proto, *args, **kwargs):
      for field in fields:
        logging.debug('Validating %s exists.', field)

        value = _value(field, input_proto)
        if not value or not os.path.exists(value):
          cros_build_lib.Die('%s path does not exist: %s' % (field, value))

      return func(input_proto, *args, **kwargs)

    return _exists

  return decorator


#pylint: disable=docstring-misnamed-args
def require(*fields):
  """Verify |fields| have all been set.

  Args:
    fields (str): The fields being checked. May be . separated nested
      fields.
  """
  assert fields

  def decorator(func):
    def _require(input_proto, *args, **kwargs):
      for field in fields:
        logging.debug('Validating %s is set.', field)

        value = _value(field, input_proto)
        if not value:
          cros_build_lib.Die('%s is required.', field)

      return func(input_proto, *args, **kwargs)

    return _require

  return decorator


def validation_complete(func):
  """Automatically skip the endpoint when called after all other validators.

  This decorator MUST be applied after all other validate decorators.
  The config can be checked manually if there is non-decorator validation, but
  this is much cleaner if it is all done in decorators.
  """
  def _validate_only(request, response, configs, *args, **kwargs):
    if configs.validate_only:
      # Avoid calling the endpoint.
      return 0
    else:
      return func(request, response, configs, *args, **kwargs)

  return _validate_only