def get_checked_field(document, name, value_type, default_value):
"""Validates and retrieves a typed field from a document.
This function attempts to look up doc[name], and raises
appropriate errors if the field is missing or not an
instance of the given type.
:param document: dict-like object
:param name: field name
:param value_type: expected value type, or '*' to accept any type
:param default_value: Default value to use if the value is missing,
or None to make the value required.
:raises: BadRequest if the field is missing or not an
instance of value_type
:returns: value obtained from doc[name]
"""
try:
value = document[name]
except KeyError:
if default_value is not None:
value = default_value
else:
description = _(u'Missing "{name}" field.').format(name=name)
raise api_errors.BadRequest(description)
# PERF(kgriffs): We do our own little spec thing because it is way
# faster than jsonschema.
if value_type == '*' or isinstance(value, value_type):
return value
description = _(u'The value of the "{name}" field must be a {vtype}.')
description = description.format(name=name, vtype=value_type.__name__)
raise api_errors.BadRequest(description)
def get_client_uuid(req):
"""Read a required Client-ID from a request.
:param req: Request object
:raises: BadRequest if the Client-ID header is missing or
does not represent a valid UUID
:returns: A UUID object
"""
try:
return uuid.UUID(req._headers.get('Client-ID'))
except ValueError:
description = _(u'Malformed hexadecimal UUID.')
raise api_errors.BadRequest(description)
