diff --git a/Doc/library/dataclasses.rst b/Doc/library/dataclasses.rst index 1457392ce6e86c..51c1a427b63787 100644 --- a/Doc/library/dataclasses.rst +++ b/Doc/library/dataclasses.rst @@ -231,7 +231,7 @@ Module contents follows a field with a default value. This is true whether this occurs in a single class, or as a result of class inheritance. -.. function:: field(*, default=MISSING, default_factory=MISSING, init=True, repr=True, hash=None, compare=True, metadata=None, kw_only=MISSING) +.. function:: field(*, default=MISSING, default_factory=MISSING, init=True, repr=True, hash=None, compare=True, metadata=None, kw_only=MISSING, doc=None) For common and simple use cases, no other functionality is required. There are, however, some dataclass features that @@ -300,6 +300,10 @@ Module contents .. versionadded:: 3.10 + - ``doc``: optional docstring for this field. + + .. versionadded:: 3.13 + If the default value of a field is specified by a call to :func:`!field`, then the class attribute for this field will be replaced by the specified *default* value. If *default* is not diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py index f5cb97edaf72cd..bdda7cc6c00f5d 100644 --- a/Lib/dataclasses.py +++ b/Lib/dataclasses.py @@ -283,11 +283,12 @@ class Field: 'compare', 'metadata', 'kw_only', + 'doc', '_field_type', # Private: not to be used by user code. ) def __init__(self, default, default_factory, init, repr, hash, compare, - metadata, kw_only): + metadata, kw_only, doc): self.name = None self.type = None self.default = default @@ -300,6 +301,7 @@ def __init__(self, default, default_factory, init, repr, hash, compare, if metadata is None else types.MappingProxyType(metadata)) self.kw_only = kw_only + self.doc = doc self._field_type = None @recursive_repr() @@ -315,6 +317,7 @@ def __repr__(self): f'compare={self.compare!r},' f'metadata={self.metadata!r},' f'kw_only={self.kw_only!r},' + f'doc={self.doc!r},' f'_field_type={self._field_type}' ')') @@ -382,7 +385,7 @@ def __repr__(self): # so that a type checker can be told (via overloads) that this is a # function whose type depends on its parameters. def field(*, default=MISSING, default_factory=MISSING, init=True, repr=True, - hash=None, compare=True, metadata=None, kw_only=MISSING): + hash=None, compare=True, metadata=None, kw_only=MISSING, doc=None): """Return an object to identify dataclass fields. default is the default value of the field. default_factory is a @@ -394,7 +397,7 @@ def field(*, default=MISSING, default_factory=MISSING, init=True, repr=True, comparison functions. metadata, if specified, must be a mapping which is stored but not otherwise examined by dataclass. If kw_only is true, the field will become a keyword-only parameter to - __init__(). + __init__(). doc is an optional docstring for this field. It is an error to specify both default and default_factory. """ @@ -402,7 +405,7 @@ def field(*, default=MISSING, default_factory=MISSING, init=True, repr=True, if default is not MISSING and default_factory is not MISSING: raise ValueError('cannot specify both default and default_factory') return Field(default, default_factory, init, repr, hash, compare, - metadata, kw_only) + metadata, kw_only, doc) def _fields_in_init_order(fields): @@ -1174,7 +1177,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen, if weakref_slot and not slots: raise TypeError('weakref_slot is True but slots is False') if slots: - cls = _add_slots(cls, frozen, weakref_slot) + cls = _add_slots(cls, frozen, weakref_slot, fields) abc.update_abstractmethods(cls) @@ -1239,7 +1242,32 @@ def _update_func_cell_for__class__(f, oldcls, newcls): return False -def _add_slots(cls, is_frozen, weakref_slot): +def _create_slots(defined_fields, inherited_slots, field_names, weakref_slot): + # The slots for our class. Remove slots from our base classes. Add + # '__weakref__' if weakref_slot was given, unless it is already present. + seen_docs = False + slots = {} + for slot in itertools.filterfalse( + inherited_slots.__contains__, + itertools.chain( + # gh-93521: '__weakref__' also needs to be filtered out if + # already present in inherited_slots + field_names, ('__weakref__',) if weakref_slot else () + ) + ): + doc = getattr(defined_fields.get(slot), 'doc', None) + if doc is not None: + seen_docs = True + slots.update({slot: doc}) + + # We only return dict if there's at least one doc member, + # otherwise we return tuple, which is the old default format. + if seen_docs: + return slots + return tuple(slots) + + +def _add_slots(cls, is_frozen, weakref_slot, defined_fields): # Need to create a new class, since we can't set __slots__ after a # class has been created, and the @dataclass decorator is called # after the class is created. @@ -1255,17 +1283,9 @@ def _add_slots(cls, is_frozen, weakref_slot): inherited_slots = set( itertools.chain.from_iterable(map(_get_slots, cls.__mro__[1:-1])) ) - # The slots for our class. Remove slots from our base classes. Add - # '__weakref__' if weakref_slot was given, unless it is already present. - cls_dict["__slots__"] = tuple( - itertools.filterfalse( - inherited_slots.__contains__, - itertools.chain( - # gh-93521: '__weakref__' also needs to be filtered out if - # already present in inherited_slots - field_names, ('__weakref__',) if weakref_slot else () - ) - ), + + cls_dict["__slots__"] = _create_slots( + defined_fields, inherited_slots, field_names, weakref_slot, ) for field_name in field_names: diff --git a/Lib/test/test_dataclasses/__init__.py b/Lib/test/test_dataclasses/__init__.py index bd2f87819a8eb0..2984f4261bd2c4 100644 --- a/Lib/test/test_dataclasses/__init__.py +++ b/Lib/test/test_dataclasses/__init__.py @@ -61,7 +61,7 @@ class C: x: int = field(default=1, default_factory=int) def test_field_repr(self): - int_field = field(default=1, init=True, repr=False) + int_field = field(default=1, init=True, repr=False, doc='Docstring') int_field.name = "id" repr_output = repr(int_field) expected_output = "Field(name='id',type=None," \ @@ -69,6 +69,7 @@ def test_field_repr(self): "init=True,repr=False,hash=None," \ "compare=True,metadata=mappingproxy({})," \ f"kw_only={MISSING!r}," \ + "doc='Docstring'," \ "_field_type=None)" self.assertEqual(repr_output, expected_output) @@ -3304,7 +3305,7 @@ class Base(Root4): j: str h: str - self.assertEqual(Base.__slots__, ('y', )) + self.assertEqual(Base.__slots__, ('y',)) @dataclass(slots=True) class Derived(Base): @@ -3314,7 +3315,7 @@ class Derived(Base): k: str h: str - self.assertEqual(Derived.__slots__, ('z', )) + self.assertEqual(Derived.__slots__, ('z',)) @dataclass class AnotherDerived(Base): @@ -3322,6 +3323,24 @@ class AnotherDerived(Base): self.assertNotIn('__slots__', AnotherDerived.__dict__) + def test_slots_with_docs(self): + class Root: + __slots__ = {'x': 'x'} + + @dataclass(slots=True) + class Base(Root): + y1: int = field(doc='y1') + y2: int + + self.assertEqual(Base.__slots__, {'y1': 'y1', 'y2': None}) + + @dataclass(slots=True) + class Child(Base): + z1: int = field(doc='z1') + z2: int + + self.assertEqual(Child.__slots__, {'z1': 'z1', 'z2': None}) + def test_cant_inherit_from_iterator_slots(self): class Root: diff --git a/Lib/test/test_pydoc/test_pydoc.py b/Lib/test/test_pydoc/test_pydoc.py index 2dba077cdea6a7..776e02f41a1cec 100644 --- a/Lib/test/test_pydoc/test_pydoc.py +++ b/Lib/test/test_pydoc/test_pydoc.py @@ -463,6 +463,14 @@ class BinaryInteger(enum.IntEnum): doc = pydoc.render_doc(BinaryInteger) self.assertIn('BinaryInteger.zero', doc) + def test_slotted_dataclass_with_field_docs(self): + import dataclasses + @dataclasses.dataclass(slots=True) + class My: + x: int = dataclasses.field(doc='Docstring for x') + doc = pydoc.render_doc(My) + self.assertIn('Docstring for x', doc) + def test_mixed_case_module_names_are_lower_cased(self): # issue16484 doc_link = get_pydoc_link(xml.etree.ElementTree) diff --git a/Misc/NEWS.d/next/Library/2024-01-14-11-43-31.gh-issue-113878.dmEIN3.rst b/Misc/NEWS.d/next/Library/2024-01-14-11-43-31.gh-issue-113878.dmEIN3.rst new file mode 100644 index 00000000000000..8e1937ab73c31b --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-01-14-11-43-31.gh-issue-113878.dmEIN3.rst @@ -0,0 +1,9 @@ +Add *doc* parameter to :func:`dataclasses.field`, so it can be stored and +shown as a documentation / metadata. If ``@dataclass(slots=True)`` is used, +then the supplied string is availabl in the :attr:`~object.__slots__` dict. +Otherwise, the supplied string is only available in the corresponding +:class:`dataclasses.Field` object. + +In order to support this feature we are changing the ``__slots__`` format +in dataclasses from :class:`tuple` to :class:`dict` +when documentation / metadata is present.