Extend dataclass constructor hinting to attrs next-gen apis.

Trivially extends dataclass constructor hinting to attrs next-gen APIs.

This will stumble in cases where attrs extends beyond the standard
dataclasses API, such as complex use of defaults, converters, et al.
However, it likely covers the vast majority of cases which fall solidly
in the intersection of the two APIs.

Extension beyond these cases could use [PEP0681 dataclass_transforms],
however this is definitely a problem for another day.

[PEP0681 dataclass_transforms]: https://peps.python.org/pep-0681/

https://github.com/davidhalter/jedi/issues/1835

jedi/plugins/stdlib.py

@@ -803,6 +803,15 @@ _implemented = {
         # For now this works at least better than Jedi trying to understand it.
         'dataclass': _dataclass
     },
+    # attrs exposes declaration interface roughly compatible with dataclasses
+    # via attrs.define, attrs.frozen and attrs.mutable
+    # https://www.attrs.org/en/stable/names.html
+    'attr': {
+        'define': _dataclass,
+    },
+    'attrs': {
+        'define': _dataclass,
+    },
     'os.path': {
         'dirname': _create_string_input_function(os.path.dirname),
         'abspath': _create_string_input_function(os.path.abspath),

test/test_inference/test_signature.py

@@ -355,6 +355,45 @@ def test_dataclass_signature(Script, skip_pre_python37, start, start_params):
     price, = sig.params[-2].infer()
     assert price.name == 'float'
 
+@pytest.mark.parametrize(
+    'start, start_params', [
+        ['@define\nclass X:', []],
+        ['@frozen\nclass X:', []],
+        ['@mutable\nclass X:', []],
+        ['@define(eq=True)\nclass X:', []],
+        [dedent('''
+         class Y():
+             y: int
+         @define
+         class X(Y):'''), []],
+        [dedent('''
+         @define
+         class Y():
+             y: int
+             z = 5
+         @define
+         class X(Y):'''), ['y']],
+    ]
+)
+def test_attrs_signature(Script, skip_pre_python37, start, start_params):
+    code = dedent('''
+            name: str
+            foo = 3
+            price: float
+            quantity: int = 0.0
+
+        X(''')
+
+    # attrs exposes two namespaces
+    code = 'from attrs import define, frozen\n' + start + code
+
+    sig, = Script(code).get_signatures()
+    assert [p.name for p in sig.params] == start_params + ['name', 'price', 'quantity']
+    quantity, = sig.params[-1].infer()
+    assert quantity.name == 'int'
+    price, = sig.params[-2].infer()
+    assert price.name == 'float'
+
 
 @pytest.mark.parametrize(
     'stmt, expected', [