[pylint] removed dunder methods in Python 3 (PLW3201)

crates/ruff_linter/resources/test/fixtures/pylint/bad_dunder_method_name.py

@@ -94,6 +94,9 @@ def __prepare__():
     def __mro_entries__(self, bases):
         pass
 
+    # Deprecated in Python 3
+    def __unicode__(self):
+        pass
 
 def __foo_bar__():  # this is not checked by the [bad-dunder-name] rule
     ...

crates/ruff_linter/src/rules/pylint/helpers.rs

@@ -307,3 +307,30 @@ pub(super) fn is_known_dunder_method(method: &str) -> bool {
             | "_generate_next_value_"
     )
 }
+
+/// Returns `true` if the method is a known dunder method that is only allowed in Python 2.
+pub(super) fn is_deprecated_dunder_method_in_python3(method: &str) -> bool {
+    matches!(
+        method,
+        "__unicode__"
+            | "__div__"
+            | "__rdiv__"
+            | "__idiv__"
+            | "__nonzero__"
+            | "__metaclass__"
+            | "__cmp__"
+            | "__getslice__"
+            | "__setslice__"
+            | "__delslice__"
+            | "__oct__"
+            | "__hex__"
+            | "__members__"
+            | "__method__"
+            | "__corece__"
+            | "__long__"
+            | "__rcmp__"
+            | "__iop__"
+            | "__rop__"
+            | "__op__"
+    )
+}

crates/ruff_linter/src/rules/pylint/rules/bad_dunder_method_name.rs

@@ -5,13 +5,20 @@ use ruff_python_ast::identifier::Identifier;
 use ruff_python_semantic::analyze::visibility;
 
 use crate::checkers::ast::Checker;
+use crate::rules::pylint::helpers::is_deprecated_dunder_method_in_python3;
 use crate::rules::pylint::helpers::is_known_dunder_method;
 
+#[derive(PartialEq, Eq, Debug)]
+enum Kind {
+    Misspelled,
+    DeprecatedInPython3,
+}
+
 /// ## What it does
-/// Checks for misspelled and unknown dunder names in method definitions.
+/// Checks for misspelled, unknown, and deprecated dunder names in method definitions.
 ///
 /// ## Why is this bad?
-/// Misspelled dunder name methods may cause your code to not function
+/// Misspelled or deprecated dunder name methods may cause your code to not function
 /// as expected.
 ///
 /// Since dunder methods are associated with customizing the behavior
@@ -45,13 +52,19 @@ use crate::rules::pylint::helpers::is_known_dunder_method;
 #[violation]
 pub struct BadDunderMethodName {
     name: String,
+    kind: Kind,
 }
 
 impl Violation for BadDunderMethodName {
     #[derive_message_formats]
     fn message(&self) -> String {
-        let BadDunderMethodName { name } = self;
-        format!("Bad or misspelled dunder method name `{name}`")
+        let BadDunderMethodName { name, kind } = self;
+        match kind {
+            Kind::Misspelled => format!("Bad or misspelled dunder method name `{name}`"),
+            Kind::DeprecatedInPython3 => {
+                format!("Deprecated dunder method name in Python 3 `{name}`")
+            }
+        }
     }
 }
 
@@ -78,9 +91,16 @@ pub(crate) fn bad_dunder_method_name(checker: &mut Checker, method: &ast::StmtFu
         return;
     }
 
+    let kind = if is_deprecated_dunder_method_in_python3(&method.name) {
+        Kind::DeprecatedInPython3
+    } else {
+        Kind::Misspelled
+    };
+
     checker.diagnostics.push(Diagnostic::new(
         BadDunderMethodName {
             name: method.name.to_string(),
+            kind,
         },
         method.identifier(),
     ));

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLW3201_bad_dunder_method_name.py.snap

@@ -58,4 +58,10 @@ bad_dunder_method_name.py:23:9: PLW3201 Bad or misspelled dunder method name `__
 25 |         pass
    |
 
-
+bad_dunder_method_name.py:98:9: PLW3201 Deprecated dunder method name in Python 3 `__unicode__`
+   |
+97 |     # Deprecated in Python 3
+98 |     def __unicode__(self):
+   |         ^^^^^^^^^^^ PLW3201
+99 |         pass
+   |