Python attr.fields() Examples

def resolve_types(cls, global_ns=None, local_ns=None):
    """
    Resolve any strings and forward annotations in type annotations.

    :param type cls: Class to resolve.
    :param globalns: Dictionary containing global variables, if needed.
    :param localns: Dictionary containing local variables, if needed.
    :raise TypeError: If *cls* is not a class.
    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
           class.
    :raise NameError: If types cannot be resolved because of missing variables.

    """
    hints = typing.get_type_hints(cls, globalns=global_ns, localns=local_ns)
    for field in attr.fields(cls):
        if field.name in hints:
            # Since fields have been frozen we must work around it.
            object.__setattr__(field, "type", hints[field.name]) 

def test_basic_annotations(self):
        """
        Sets the `Attribute.type` attr from basic type annotations.
        """

        @attr.s
        class C:
            x: int = attr.ib()
            y = attr.ib(type=str)
            z = attr.ib()

        assert int is attr.fields(C).x.type
        assert str is attr.fields(C).y.type
        assert None is attr.fields(C).z.type
        assert C.__init__.__annotations__ == {
            "x": int,
            "y": str,
            "return": None,
        } 

def test_fallback(cl_and_vals):
    """The fallback case works."""
    cl, vals = cl_and_vals

    assume(attr.fields(cl))  # At least one field.

    @attr.s
    class A(object):
        pass

    fn = create_uniq_field_dis_func(A, cl)

    assert fn({}) is A
    assert fn(attr.asdict(cl(*vals))) is cl

    attr_names = {a.name for a in attr.fields(cl)}

    if "xyz" not in attr_names:
        fn({"xyz": 1}) is A  # Uses the fallback. 

def _to_type_from_attrs(spec) -> Type:
  """Converts an `attr.s` class or instance to a `tff.Type`."""
  if isinstance(spec, type):
    # attrs class type, introspect the attributes for their type annotations.
    elements = [(a.name, a.type) for a in attr.fields(spec)]
    missing_types = [n for (n, t) in elements if not t]
    if missing_types:
      raise TypeError((
          "Cannot infer tff.Type for attr.s class '{}' because some attributes "
          'were missing type specifications: {}').format(
              spec.__name__, missing_types))
    the_type = spec
  else:
    # attrs class instance, inspect the field values for instances convertible
    # to types.
    elements = attr.asdict(
        spec, dict_factory=collections.OrderedDict, recurse=False)
    the_type = type(spec)

  return NamedTupleTypeWithPyContainerType(elements, the_type) 

def test_structure_simple_from_dict_default(converter, cl_and_vals, data):
    """Test structuring non-nested attrs classes with default value."""
    cl, vals = cl_and_vals
    obj = cl(*vals)
    attrs_with_defaults = [a for a in fields(cl) if a.default is not NOTHING]
    to_remove = data.draw(
        lists(elements=sampled_from(attrs_with_defaults), unique=True)
    )

    for a in to_remove:
        if isinstance(a.default, Factory):
            setattr(obj, a.name, a.default.factory())
        else:
            setattr(obj, a.name, a.default)

    dumped = asdict(obj)

    for a in to_remove:
        del dumped[a.name]

    assert obj == converter.structure(dumped, cl) 

def test_structure_union_none(converter, cl_and_vals_a, cl_and_vals_b):
    """Structuring of automatically-disambiguable unions works."""
    cl_a, vals_a = cl_and_vals_a
    cl_b, vals_b = cl_and_vals_b
    a_field_names = {a.name for a in fields(cl_a)}
    b_field_names = {a.name for a in fields(cl_b)}
    assume(a_field_names)
    assume(b_field_names)

    common_names = a_field_names & b_field_names
    if len(a_field_names) > len(common_names):
        obj = cl_a(*vals_a)
        dumped = asdict(obj)
        res = converter.structure(dumped, Union[cl_a, cl_b, None])
        assert isinstance(res, cl_a)
        assert obj == res

    assert converter.structure(None, Union[cl_a, cl_b, None]) is None 

def test_structure_union(converter, cl_and_vals_a, cl_and_vals_b):
    """Structuring of automatically-disambiguable unions works."""
    cl_a, vals_a = cl_and_vals_a
    cl_b, vals_b = cl_and_vals_b
    a_field_names = {a.name for a in fields(cl_a)}
    b_field_names = {a.name for a in fields(cl_b)}
    assume(a_field_names)
    assume(b_field_names)

    common_names = a_field_names & b_field_names
    if len(a_field_names) > len(common_names):
        obj = cl_a(*vals_a)
        dumped = asdict(obj)
        res = converter.structure(dumped, Union[cl_a, cl_b])
        assert isinstance(res, cl_a)
        assert obj == res 

def test_disambiguation(cl_and_vals_a, cl_and_vals_b):
    """Disambiguation should work when there are unique fields."""
    cl_a, vals_a = cl_and_vals_a
    cl_b, vals_b = cl_and_vals_b

    req_a = {a.name for a in attr.fields(cl_a)}
    req_b = {a.name for a in attr.fields(cl_b)}

    assume(len(req_a))
    assume(len(req_b))

    assume((req_a - req_b) or (req_b - req_a))

    fn = create_uniq_field_dis_func(cl_a, cl_b)

    assert fn(attr.asdict(cl_a(*vals_a))) is cl_a 

def test_unit_suffix():
    class Foo(DumpableAttrs):
        xs: int = with_units("xs")
        ys: int = with_units("ys", default=2)
        no_unit: int = 3

    # Assert class constructor works.
    foo = Foo(1, 2, 3)
    foo_default = Foo(1)

    # Assert units work.
    foo_fields = attr.fields(Foo)
    assert get_units(foo_fields.xs) == " xs"
    assert get_units(foo_fields.ys) == " ys"
    assert get_units(foo_fields.no_unit) == ""


# Dataclass dump testing 

def _to_config(config_cls, default_get, environ, prefix):
    vals = {}
    for a in attr.fields(config_cls):
        try:
            ce = a.metadata[CNF_KEY]
        except KeyError:
            continue
        if ce.sub_cls is None:
            get = ce.callback or default_get
            val = get(environ, a.metadata, prefix, a.name)
        else:
            val = _to_config(
                ce.sub_cls,
                default_get,
                environ,
                prefix + ((a.name if prefix else a.name),),
            )

        vals[a.name] = val
    return config_cls(**vals) 

def _to_config(config_cls, default_get, environ, prefix):
    vals = {}
    for a in attr.fields(config_cls):
        try:
            ce = a.metadata[CNF_KEY]
        except KeyError:
            continue
        if ce.sub_cls is None:
            get = ce.callback or default_get
            val = get(environ, a.metadata, prefix, a.name)
        else:
            val = _to_config(
                ce.sub_cls, default_get, environ,
                prefix + ((a.name if prefix else a.name),)
            )

        vals[a.name] = val
    return config_cls(**vals) 

def from_pipfile(cls, name, pipfile):
        # type: (S, TPIPFILE) -> NamedRequirement
        creation_args = {}  # type: TPIPFILE
        if hasattr(pipfile, "keys"):
            attr_fields = [field.name for field in attr.fields(cls)]
            creation_args = {
                k: v for k, v in pipfile.items() if k in attr_fields
            }  # type: ignore
        creation_args["name"] = name
        version = get_version(pipfile)  # type: Optional[STRING_TYPE]
        extras = creation_args.get("extras", None)
        creation_args["version"] = version  # type: ignore
        req = init_requirement("{0}{1}".format(name, version))
        if req and extras and req.extras and isinstance(req.extras, tuple):
            if isinstance(extras, six.string_types):
                req.extras = (extras) + tuple(["{0}".format(xtra) for xtra in req.extras])
            elif isinstance(extras, (tuple, list)):
                req.extras += tuple(extras)
        creation_args["req"] = req
        return cls(**creation_args)  # type: ignore 

def test_load_post_init():
    """ yaml.load() does not natively call __init__.
    So DumpableAttrs modifies __setstate__ to call __attrs_post_init__. """

    class Foo(DumpableAttrs):
        foo: int

        def __attrs_post_init__(self):
            self.foo = 99

    s = """\
!Foo
foo: 0
"""
    assert yaml.load(s) == Foo(99)


# Test handling of _prefix fields, or init=False 

def test_typing_annotations(self):
        """
        Sets the `Attribute.type` attr from typing annotations.
        """

        @attr.s
        class C:
            x: typing.List[int] = attr.ib()
            y = attr.ib(type=typing.Optional[str])

        assert typing.List[int] is attr.fields(C).x.type
        assert typing.Optional[str] is attr.fields(C).y.type
        assert C.__init__.__annotations__ == {
            "x": typing.List[int],
            "y": typing.Optional[str],
            "return": None,
        } 

def test_metadata_immutability(self, C, string):
        """
        The metadata dict should be best-effort immutable.
        """
        for a in fields(C):
            with pytest.raises(TypeError):
                a.metadata[string] = string
            with pytest.raises(AttributeError):
                a.metadata.update({string: string})
            with pytest.raises(AttributeError):
                a.metadata.clear()
            with pytest.raises(AttributeError):
                a.metadata.setdefault(string, string)

            for k in a.metadata:
                # For some reason, Python 3's MappingProxyType throws an
                # IndexError for deletes on a large integer key.
                with pytest.raises((TypeError, IndexError)):
                    del a.metadata[k]
                with pytest.raises(AttributeError):
                    a.metadata.pop(k)
            with pytest.raises(AttributeError):
                a.metadata.popitem() 

def test_metadata_present(self, list_of_attrs):
        """
        Assert dictionaries are copied and present.
        """
        C = make_class("C", dict(zip(gen_attr_names(), list_of_attrs)))

        for hyp_attr, class_attr in zip(list_of_attrs, fields(C)):
            if hyp_attr.metadata is None:
                # The default is a singleton empty dict.
                assert class_attr.metadata is not None
                assert len(class_attr.metadata) == 0
            else:
                assert hyp_attr.metadata == class_attr.metadata

                # Once more, just to assert getting items and iteration.
                for k in class_attr.metadata:
                    assert hyp_attr.metadata[k] == class_attr.metadata[k]
                    assert hyp_attr.metadata.get(k) == class_attr.metadata.get(
                        k
                    ) 

def test_recurse_property(self, cls, tuple_class):
        """
        Property tests for recursive astuple.
        """
        obj = cls()
        obj_tuple = astuple(obj, tuple_factory=tuple_class)

        def assert_proper_tuple_class(obj, obj_tuple):
            assert isinstance(obj_tuple, tuple_class)
            for index, field in enumerate(fields(obj.__class__)):
                field_val = getattr(obj, field.name)
                if has(field_val.__class__):
                    # This field holds a class, recurse the assertions.
                    assert_proper_tuple_class(field_val, obj_tuple[index])

        assert_proper_tuple_class(obj, obj_tuple) 

def test_change(self, C, data):
        """
        Changes work.
        """
        # Take the first attribute, and change it.
        assume(fields(C))  # Skip classes with no attributes.
        field_names = [a.name for a in fields(C)]
        original = C()
        chosen_names = data.draw(st.sets(st.sampled_from(field_names)))
        change_dict = {name: data.draw(st.integers()) for name in chosen_names}

        with pytest.deprecated_call():
            changed = assoc(original, **change_dict)

        for k, v in change_dict.items():
            assert getattr(changed, k) == v 

def test_change(self, C, data):
        """
        Changes work.
        """
        # Take the first attribute, and change it.
        assume(fields(C))  # Skip classes with no attributes.
        field_names = [a.name for a in fields(C)]
        original = C()
        chosen_names = data.draw(st.sets(st.sampled_from(field_names)))
        # We pay special attention to private attributes, they should behave
        # like in `__init__`.
        change_dict = {
            name.replace("_", ""): data.draw(st.integers())
            for name in chosen_names
        }
        changed = evolve(original, **change_dict)
        for name in chosen_names:
            assert getattr(changed, name) == change_dict[name.replace("_", "")] 

def __init__(self, strategy, source="<string>"):
        self._config = ConfigParser(default_section="strategy", interpolation=None)
        self._config.read_string(strategy, source)

        self._situations = dict()
        for name in self._config.sections():
            # configparser set non-specified values to '', we want default to None
            attr_names = [a.name for a in attr.fields(_Situation)]
            values = dict.fromkeys(attr_names, None)
            for key, val in self._config[name].items():
                # filter out fields not implemented, otherwise it would
                # cause TypeError for _Situation constructor
                if (not val) or (key not in attr_names):
                    continue
                elif key in _POSITIONS:
                    values[key] = Range(val)
                else:
                    values[key] = val
            self._situations[name] = _Situation(**values)

        self._tuple = tuple(self._situations.values()) 

def from_pipfile(cls, name, pipfile):
        attr_fields = [field.name for field in attr.fields(cls)]
        found_keys = [k for k in pipfile.keys() if k in attr_fields]
        marker_strings = ["{0} {1}".format(k, pipfile[k]) for k in found_keys]
        if pipfile.get("markers"):
            marker_strings.append(pipfile.get("markers"))
        markers = set()
        for marker in marker_strings:
            markers.add(marker)
        combined_marker = None
        try:
            combined_marker = cls.make_marker(" and ".join(sorted(markers)))
        except RequirementError:
            pass
        else:
            return combined_marker 

def test_dump_load_ignored():
    """ Ensure loading `xx=Ignored` works.
    Does not check constructor `Config(xx=1)`.
    """

    class Config(DumpableAttrs):
        xx = Ignored

    # Test dumping
    assert len(attr.fields(Config)) == 0
    cfg = Config()
    s = yaml.dump(cfg)
    assert (
        s
        == """\
!Config {}
"""
    )
    assert yaml.load(s) == cfg

    # Test loading
    s = """\
!Config
xx: 1
"""
    assert yaml.load(s) == Config() 

def test_recurse_property(self, cls, dict_class):
        """
        Property tests for recursive asdict.
        """
        obj = cls()
        obj_dict = asdict(obj, dict_factory=dict_class)

        def assert_proper_dict_class(obj, obj_dict):
            assert isinstance(obj_dict, dict_class)

            for field in fields(obj.__class__):
                field_val = getattr(obj, field.name)
                if has(field_val.__class__):
                    # This field holds a class, recurse the assertions.
                    assert_proper_dict_class(field_val, obj_dict[field.name])
                elif isinstance(field_val, Sequence):
                    dict_val = obj_dict[field.name]
                    for item, item_dict in zip(field_val, dict_val):
                        if has(item.__class__):
                            assert_proper_dict_class(item, item_dict)
                elif isinstance(field_val, Mapping):
                    # This field holds a dictionary.
                    assert isinstance(obj_dict[field.name], dict_class)

                    for key, val in field_val.items():
                        if has(val.__class__):
                            assert_proper_dict_class(
                                val, obj_dict[field.name][key]
                            )

        assert_proper_dict_class(obj, obj_dict) 

def test_only_attrs_annotations_collected(self):
        """
        Annotations that aren't set to an attr.ib are ignored.
        """

        @attr.s
        class C:
            x: typing.List[int] = attr.ib()
            y: int

        assert 1 == len(attr.fields(C))
        assert C.__init__.__annotations__ == {
            "x": typing.List[int],
            "return": None,
        } 

def test_allow(self, incl, value):
        """
        Return True if a class or attribute is whitelisted.
        """
        i = include(*incl)
        assert i(fields(C).a, value) is True 

def test_drop_class(self, incl, value):
        """
        Return False on non-whitelisted classes and attributes.
        """
        i = include(*incl)
        assert i(fields(C).a, value) is False 

def test_allow(self, excl, value):
        """
        Return True if class or attribute is not blacklisted.
        """
        e = exclude(*excl)
        assert e(fields(C).a, value) is True 

def test_exclude_dump():
    """
    Test that the exclude="" parameter can remove fields from always_dump="*".
    """

    class Config(DumpableAttrs, always_dump="*", exclude="b"):
        a: int = 1
        b: int = 2

    s = yaml.dump(Config())
    assert (
        s
        == """\
!Config
a: 1
"""
    )

    class Special(Config, exclude="d"):
        c: int = 3
        d: int = 4

    s = yaml.dump(Special())
    assert (
        s
        == """\
!Special
a: 1
c: 3
"""
    )


# Dataclass load testing 

def test_ignore_unrecognized_fields():
    """Ensure unrecognized fields yield warning, not exception."""

    class Foo(DumpableAttrs):
        foo: int

    s = """\
!Foo
foo: 1
bar: 2
"""
    with pytest.warns(CorrWarning):
        assert yaml.load(s) == Foo(1) 

def test_fields(self, cls):
        """
        `attr.fields` works.
        """
        assert (
            Attribute(
                name="x",
                default=foo,
                validator=None,
                repr=True,
                cmp=None,
                eq=True,
                order=True,
                hash=None,
                init=True,
                inherited=False,
            ),
            Attribute(
                name="y",
                default=attr.Factory(list),
                validator=None,
                repr=True,
                cmp=None,
                eq=True,
                order=True,
                hash=None,
                init=True,
                inherited=False,
            ),
        ) == attr.fields(cls)