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Add __dataclass_fields__ and __attrs_attrs__ to dataclasses #8578

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merged 18 commits into from
Aug 20, 2021
Merged

Add __dataclass_fields__ and __attrs_attrs__ to dataclasses #8578

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07f8894
Add __attrs_attrs__ attribute to attr.s decorated classes
tkukushkin Mar 23, 2020
abfe951
Add __dataclass_fields__ attribute to dataclasses
tkukushkin Mar 23, 2020
4a8688e
Add explicit Any as type argument to dataclasses.Field and attr.Attri…
tkukushkin Mar 27, 2020
17a9403
Fix some tests
tkukushkin Mar 27, 2020
229c568
Fix almost all tests
tkukushkin Mar 29, 2020
426d644
Remove commented code from stub
tkukushkin Mar 29, 2020
0b97db1
Merge branch 'master' into fix-6568
tkukushkin Oct 11, 2020
8dadb8a
Fix narrowing tests
tkukushkin Oct 11, 2020
62b8497
Fix test
tkukushkin Oct 11, 2020
7b26c67
Fix mypy errors
tkukushkin Oct 11, 2020
a5bcda1
Fix flake8 errors
tkukushkin Oct 11, 2020
e75b83a
Merge branch 'master' into fix-6568
tkukushkin Jan 16, 2021
0932037
Fix tests
tkukushkin Jan 17, 2021
3a66912
Merge branch 'master' of github.com:python/mypy into fix-6568
tkukushkin Aug 13, 2021
2d3a6ca
Generate precise type for `__attrs_attrs__` in attrs plugin
tkukushkin Aug 13, 2021
e932c50
Fix self mypy check
tkukushkin Aug 13, 2021
be97c26
Fix tests
tkukushkin Aug 16, 2021
528d587
Delete stray file
tkukushkin Aug 20, 2021
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16 changes: 16 additions & 0 deletions mypy/plugins/attrs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -278,6 +278,8 @@ def attr_class_maker_callback(ctx: 'mypy.plugin.ClassDefContext',
ctx.api.defer()
return

_add_attrs_magic_attribute(ctx)

# Save the attributes so that subclasses can reuse them.
ctx.cls.info.metadata['attrs'] = {
'attributes': [attr.serialize() for attr in attributes],
Expand Down Expand Up @@ -656,6 +658,20 @@ def _add_init(ctx: 'mypy.plugin.ClassDefContext', attributes: List[Attribute],
adder.add_method('__init__', args, NoneType())


def _add_attrs_magic_attribute(ctx: 'mypy.plugin.ClassDefContext') -> None:
attr_name = '__attrs_attrs__'
attr_type = ctx.api.named_type('__builtins__.tuple', [
ctx.api.named_type('attr.Attribute'),
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@ilevkivskyi ctx.api.named_type is for builtin types, but what i should use instead of it?

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It is not for builtin types, it is for types that are guaranteed to be present (i.e. loaded).

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@ilevkivskyi, and how to ensure that attr.Attribute is loaded? Or maybe need to use Any if it is not loaded?

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They should be loaded, because the attr module must be analyzed if this plugin is called. The tests fail because they run with partial stubs, not the real ones, see for example https://github.com/python/mypy/blob/master/test-data/unit/lib-stub/attr.pyi, Attribute is not present there.

Also the latter is generic, so I would explicitly add a type argument here (even if it is Any).

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They should be loaded, because the attr module must be analyzed if this plugin is called.

I have a problem with different styles of import of attr.

This example works fine:

import attr

@attr.s
class Foo:
    pass

class AttrsProtocol(Protocol):
    __attrs_attrs__: Tuple[attr.Attribute, ...]

def foo(x: AttrsProtocol) -> None:
    pass

foo(Foo())

But if I change import to:

from attr import attrs, Attribute

@attrs
class Foo:
    pass

I get exception:

  File "/Users/tkukushkin/Projects/mypy/mypy/plugins/attrs.py", line 664, in _add_attrs_magic_attribute
    ctx.api.named_type('attr.Attribute'),
  File "/Users/tkukushkin/Projects/mypy/mypy/semanal.py", line 4143, in named_type
    assert sym, "Internal error: attempted to construct unknown type"
AssertionError: Internal error: attempted to construct unknown type

Some tests fail because of this.

The tests fail because they run with partial stubs, not the real ones, see for example https://github.com/python/mypy/blob/master/test-data/unit/lib-stub/attr.pyi, Attribute is not present there.

Yes, I already added Attribute to stub, but not pushed yet.

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Well, I just looked at the code of named_type() and it is horrible, it uses lookup_qualified() (which is just a normal symbol lookup following Python name resolution rules) so I wonder how it ever worked. You can try using named_type_or_none() instead, that one looks reasonable.

Another option is to actually fix named_type(), but it may be not the best task as a first contribution.

])
var = Var(name=attr_name, type=attr_type)
var.info = ctx.cls.info
ctx.cls.info.names[attr_name] = SymbolTableNode(
kind=MDEF,
node=var,
plugin_generated=True,
)


class MethodAdder:
"""Helper to add methods to a TypeInfo.

Expand Down
17 changes: 17 additions & 0 deletions mypy/plugins/dataclasses.py
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Original file line number Diff line number Diff line change
Expand Up @@ -183,6 +183,8 @@ def transform(self) -> None:

self.reset_init_only_vars(info, attributes)

self._add_dataclass_fields_magic_attribute()

info.metadata['dataclass'] = {
'attributes': [attr.serialize() for attr in attributes],
'frozen': decorator_arguments['frozen'],
Expand Down Expand Up @@ -361,6 +363,21 @@ def _freeze(self, attributes: List[DataclassAttribute]) -> None:
var._fullname = info.fullname + '.' + var.name
info.names[var.name] = SymbolTableNode(MDEF, var)

def _add_dataclass_fields_magic_attribute(self) -> None:
attr_name = '__dataclass_fields__'
dataclass_field_type = self._ctx.api.named_type('dataclasses.Field')
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Same comment here.

attr_type = self._ctx.api.named_type('__builtins__.dict', [
self._ctx.api.named_type('__builtins__.str'),
dataclass_field_type,
])
var = Var(name=attr_name, type=attr_type)
var.info = self._ctx.cls.info
self._ctx.cls.info.names[attr_name] = SymbolTableNode(
kind=MDEF,
node=var,
plugin_generated=True,
)


def dataclass_class_maker_callback(ctx: ClassDefContext) -> None:
"""Hooks into the class typechecking process to add support for dataclasses.
Expand Down