Allow descriptor instantiations in dataclass fields (#5537)

## Summary

Per the Python documentation, dataclasses are allowed to instantiate
descriptors, like so:

```python
class IntConversionDescriptor:
  def __init__(self, *, default):
    self._default = default

  def __set_name__(self, owner, name):
    self._name = "_" + name

  def __get__(self, obj, type):
    if obj is None:
      return self._default

    return getattr(obj, self._name, self._default)

  def __set__(self, obj, value):
    setattr(obj, self._name, int(value))

@dataclass
class InventoryItem:
  quantity_on_hand: IntConversionDescriptor = IntConversionDescriptor(default=100)
```

Closes https://github.com/astral-sh/ruff/issues/4451.

crates/ruff/resources/test/fixtures/ruff/RUF009.py

@@ -6,6 +6,7 @@ from fractions import Fraction
 from pathlib import Path
 from typing import ClassVar, NamedTuple
 
+
 def default_function() -> list[int]:
     return []
 
@@ -25,12 +26,13 @@ class A:
     fine_timedelta: datetime.timedelta = datetime.timedelta(hours=7)
     fine_tuple: tuple[int] = tuple([1])
     fine_regex: re.Pattern = re.compile(r".*")
-    fine_float: float = float('-inf')
+    fine_float: float = float("-inf")
     fine_int: int = int(12)
     fine_complex: complex = complex(1, 2)
     fine_str: str = str("foo")
     fine_bool: bool = bool("foo")
-    fine_fraction: Fraction = Fraction(1,2)
+    fine_fraction: Fraction = Fraction(1, 2)
+
 
 DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES = ImmutableType(40)
 DEFAULT_A_FOR_ALL_DATACLASSES = A([1, 2, 3])
@@ -45,3 +47,25 @@ class B:
     okay_variant: A = DEFAULT_A_FOR_ALL_DATACLASSES
 
     fine_dataclass_function: list[int] = field(default_factory=list)
+
+
+class IntConversionDescriptor:
+    def __init__(self, *, default):
+        self._default = default
+
+    def __set_name__(self, owner, name):
+        self._name = "_" + name
+
+    def __get__(self, obj, type):
+        if obj is None:
+            return self._default
+
+        return getattr(obj, self._name, self._default)
+
+    def __set__(self, obj, value):
+        setattr(obj, self._name, int(value))
+
+
+@dataclass
+class InventoryItem:
+    quantity_on_hand: IntConversionDescriptor = IntConversionDescriptor(default=100)

crates/ruff/src/rules/ruff/rules/function_call_in_dataclass_default.rs

@@ -8,7 +8,7 @@ use ruff_python_semantic::analyze::typing::is_immutable_func;
 
 use crate::checkers::ast::Checker;
 use crate::rules::ruff::rules::helpers::{
-    is_class_var_annotation, is_dataclass, is_dataclass_field,
+    is_class_var_annotation, is_dataclass, is_dataclass_field, is_descriptor_class,
 };
 
 /// ## What it does
@@ -98,6 +98,7 @@ pub(crate) fn function_call_in_dataclass_default(
                 if !is_class_var_annotation(annotation, checker.semantic())
                     && !is_immutable_func(func, checker.semantic(), &extend_immutable_calls)
                     && !is_dataclass_field(func, checker.semantic())
+                    && !is_descriptor_class(func, checker.semantic())
                 {
                     checker.diagnostics.push(Diagnostic::new(
                         FunctionCallInDataclassDefaultArgument {

crates/ruff/src/rules/ruff/rules/helpers.rs

@@ -1,7 +1,7 @@
 use rustpython_parser::ast::{self, Expr};
 
 use ruff_python_ast::helpers::map_callable;
-use ruff_python_semantic::SemanticModel;
+use ruff_python_semantic::{BindingKind, SemanticModel};
 
 /// Return `true` if the given [`Expr`] is a special class attribute, like `__slots__`.
 ///
@@ -64,3 +64,22 @@ pub(super) fn is_pydantic_model(class_def: &ast::StmtClassDef, semantic: &Semant
         })
     })
 }
+
+/// Returns `true` if the given function is an instantiation of a class that implements the
+/// descriptor protocol.
+///
+/// See: <https://docs.python.org/3.10/reference/datamodel.html#descriptors>
+pub(super) fn is_descriptor_class(func: &Expr, semantic: &SemanticModel) -> bool {
+    semantic.lookup_attribute(func).map_or(false, |id| {
+        let BindingKind::ClassDefinition(scope_id) = semantic.binding(id).kind else {
+            return false;
+        };
+
+        // Look for `__get__`, `__set__`, and `__delete__` methods.
+        ["__get__", "__set__", "__delete__"].iter().any(|method| {
+            semantic.scopes[scope_id].get(method).map_or(false, |id| {
+                semantic.binding(id).kind.is_function_definition()
+            })
+        })
+    })
+}

crates/ruff/src/rules/ruff/snapshots/ruff__rules__ruff__tests__RUF009_RUF009.py.snap

@@ -1,44 +1,44 @@
 ---
 source: crates/ruff/src/rules/ruff/mod.rs
 ---
-RUF009.py:19:41: RUF009 Do not perform function call `default_function` in dataclass defaults
+RUF009.py:20:41: RUF009 Do not perform function call `default_function` in dataclass defaults
    |
-17 | @dataclass()
+18 | @dataclass()
-18 | class A:
+19 | class A:
-19 |     hidden_mutable_default: list[int] = default_function()
+20 |     hidden_mutable_default: list[int] = default_function()
    |                                         ^^^^^^^^^^^^^^^^^^ RUF009
-20 |     class_variable: typing.ClassVar[list[int]] = default_function()
+21 |     class_variable: typing.ClassVar[list[int]] = default_function()
-21 |     another_class_var: ClassVar[list[int]] = default_function()
+22 |     another_class_var: ClassVar[list[int]] = default_function()
    |
 
-RUF009.py:41:41: RUF009 Do not perform function call `default_function` in dataclass defaults
+RUF009.py:43:41: RUF009 Do not perform function call `default_function` in dataclass defaults
    |
-39 | @dataclass
+41 | @dataclass
-40 | class B:
+42 | class B:
-41 |     hidden_mutable_default: list[int] = default_function()
+43 |     hidden_mutable_default: list[int] = default_function()
    |                                         ^^^^^^^^^^^^^^^^^^ RUF009
-42 |     another_dataclass: A = A()
+44 |     another_dataclass: A = A()
-43 |     not_optimal: ImmutableType = ImmutableType(20)
+45 |     not_optimal: ImmutableType = ImmutableType(20)
    |
 
-RUF009.py:42:28: RUF009 Do not perform function call `A` in dataclass defaults
+RUF009.py:44:28: RUF009 Do not perform function call `A` in dataclass defaults
    |
-40 | class B:
+42 | class B:
-41 |     hidden_mutable_default: list[int] = default_function()
+43 |     hidden_mutable_default: list[int] = default_function()
-42 |     another_dataclass: A = A()
+44 |     another_dataclass: A = A()
    |                            ^^^ RUF009
-43 |     not_optimal: ImmutableType = ImmutableType(20)
+45 |     not_optimal: ImmutableType = ImmutableType(20)
-44 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
+46 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
    |
 
-RUF009.py:43:34: RUF009 Do not perform function call `ImmutableType` in dataclass defaults
+RUF009.py:45:34: RUF009 Do not perform function call `ImmutableType` in dataclass defaults
    |
-41 |     hidden_mutable_default: list[int] = default_function()
+43 |     hidden_mutable_default: list[int] = default_function()
-42 |     another_dataclass: A = A()
+44 |     another_dataclass: A = A()
-43 |     not_optimal: ImmutableType = ImmutableType(20)
+45 |     not_optimal: ImmutableType = ImmutableType(20)
    |                                  ^^^^^^^^^^^^^^^^^ RUF009
-44 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
+46 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
-45 |     okay_variant: A = DEFAULT_A_FOR_ALL_DATACLASSES
+47 |     okay_variant: A = DEFAULT_A_FOR_ALL_DATACLASSES
    |