dict_keys issue with python-3.7

[Alexis PRAYEZ]

Hi folks,

I know python-3.7 is not officially supported, but the readme says to report issues with python>3.6 so here I am !

We are running our automated tests on python-2.7.15 and  python-3.7.2 and never had any issue until now.

We recently upgraded from mongoengine-0.16.2 to mongoengine-0.18.1 and we started seeing the following errors

[gw3] win32 -- Python 3.7.2 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

[...]

    def __init__(self, *args, **values):

        """

        Initialise a document or an embedded document.

    

        :param dict values: A dictionary of keys and values for the document.

            It may contain additional reserved keywords, e.g. "__auto_convert".

        :param bool __auto_convert: If True, supplied values will be converted

            to Python-type values via each field's `to_python` method.

        :param set __only_fields: A set of fields that have been loaded for

            this document. Empty if all fields have been loaded.

        :param bool _created: Indicates whether this is a brand new document

            or whether it's already been persisted before. Defaults to true.

        """

        self._initialised = False

        self._created = True

    

        if args:

            # Combine positional arguments with named arguments.

            # We only want named arguments.

            field = iter(self._fields_ordered)

            # If its an automatic id field then skip to the first defined field

            if getattr(self, '_auto_id_field', False):

                next(field)

            for value in args:

                name = next(field)

                if name in values:

                    raise TypeError(

                        'Multiple values for keyword argument "%s"' % name)

                values[name] = value

    

        __auto_convert = values.pop('__auto_convert', True)

    

        __only_fields = set(values.pop('__only_fields', values))

    

        _created = values.pop('_created', True)

    

        signals.pre_init.send(self.__class__, document=self, values=values)

    

        # Check if there are undefined fields supplied to the constructor,

        # if so raise an Exception.

        if not self._dynamic and (self._meta.get('strict', True) or _created):

            _undefined_fields = set(values.keys()) - set(

>               self._fields.keys() + ['id', 'pk', '_cls', '_text_score'])

E           TypeError: unsupported operand type(s) for +: 'dict_keys' and 'list'

[...]\0.18.1\python\mongoengine\base\document.py:88: TypeError

[gw0] win32 -- Python 3.7.2 

[...]

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

[...]

[...]\0.18.1\python\mongoengine\document.py:712: in reload

    **self._object_key).only(*fields).limit(

[...]\0.18.1\python\mongoengine\queryset\base.py:919: in only

    return self.fields(True, **fields)

[...]\0.18.1\python\mongoengine\queryset\base.py:989: in fields

    queryset = self.clone()

[...]\0.18.1\python\mongoengine\queryset\base.py:734: in clone

    return self._clone_into(self.__class__(self._document, self._collection_obj))

[...]\0.18.1\python\mongoengine\queryset\base.py:755: in _clone_into

    setattr(new_qs, prop, copy.copy(val))

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

x = dict_keys(['versions'])

    def copy(x):

        """Shallow copy operation on arbitrary Python objects.

    

        See the module's __doc__ string for more info.

        """

    

        cls = type(x)

    

        copier = _copy_dispatch.get(cls)

        if copier:

            return copier(x)

    

        try:

            issc = issubclass(cls, type)

        except TypeError: # cls is not a class

            issc = False

        if issc:

            # treat it as a regular class:

            return _copy_immutable(x)

    

        copier = getattr(cls, "__copy__", None)

        if copier:

            return copier(x)

    

        reductor = dispatch_table.get(cls)

        if reductor:

            rv = reductor(x)

        else:

            reductor = getattr(x, "__reduce_ex__", None)

            if reductor:

>               rv = reductor(4)

E               TypeError: can't pickle dict_keys objects

[...]\python\3.7\Lib\copy.py:96: TypeError

Both relates to the change of dict.keys() returning a view object 

Can you confirm this issue ?

Should I open one, two or as many issues as there are instances of this errror I encounter, or one global issue ?

Cheers,

Alexis