[flake8-bugbear] Treat raise NotImplemented-only bodies as stub functions

crates/ruff_linter/resources/test/fixtures/flake8_bugbear/B006_8.py

@@ -0,0 +1,20 @@
+def foo(a: list = []):
+    raise NotImplementedError("")
+
+
+def bar(a: dict = {}):
+    """ This one also has a docstring"""
+    raise NotImplementedError("and has some text in here")
+
+
+def baz(a: list = []):
+    """This one raises a different exception"""
+    raise IndexError()
+
+
+def qux(a: list = []):
+    raise NotImplementedError
+
+
+def quux(a: list = []):
+    raise NotImplemented

crates/ruff_linter/src/rules/flake8_bugbear/mod.rs

@@ -41,6 +41,7 @@ mod tests {
     #[test_case(Rule::MutableArgumentDefault, Path::new("B006_5.py"))]
     #[test_case(Rule::MutableArgumentDefault, Path::new("B006_6.py"))]
     #[test_case(Rule::MutableArgumentDefault, Path::new("B006_7.py"))]
+    #[test_case(Rule::MutableArgumentDefault, Path::new("B006_8.py"))]
     #[test_case(Rule::MutableArgumentDefault, Path::new("B006_B008.py"))]
     #[test_case(Rule::NoExplicitStacklevel, Path::new("B028.py"))]
     #[test_case(Rule::RaiseLiteral, Path::new("B016.py"))]

crates/ruff_linter/src/rules/flake8_bugbear/rules/mutable_argument_default.rs

@@ -1,11 +1,12 @@
 use ruff_diagnostics::{Diagnostic, Edit, Fix, FixAvailability, Violation};
 use ruff_macros::{derive_message_formats, violation};
-use ruff_python_ast::helpers::is_docstring_stmt;
+use ruff_python_ast::helpers::{is_docstring_stmt, map_callable};
 use ruff_python_ast::name::QualifiedName;
-use ruff_python_ast::{self as ast, Expr, Parameter, ParameterWithDefault, Stmt};
+use ruff_python_ast::{self as ast, Expr, Parameter, ParameterWithDefault, Stmt, StmtRaise};
 use ruff_python_codegen::{Generator, Stylist};
 use ruff_python_index::Indexer;
 use ruff_python_semantic::analyze::typing::{is_immutable_annotation, is_mutable_expr};
+use ruff_python_semantic::SemanticModel;
 use ruff_python_trivia::{indentation_at_offset, textwrap};
 use ruff_source_file::Locator;
 use ruff_text_size::Ranged;
@@ -118,6 +119,7 @@ pub(crate) fn mutable_argument_default(checker: &mut Checker, function_def: &ast
                 function_def,
                 parameter,
                 default,
+                checker.semantic(),
                 checker.locator(),
                 checker.stylist(),
                 checker.indexer(),
@@ -132,10 +134,12 @@ pub(crate) fn mutable_argument_default(checker: &mut Checker, function_def: &ast
 
 /// Generate a [`Fix`] to move a mutable argument default initialization
 /// into the function body.
+#[allow(clippy::too_many_arguments)]
 fn move_initialization(
     function_def: &ast::StmtFunctionDef,
     parameter: &Parameter,
     default: &Expr,
+    semantic: &SemanticModel,
     locator: &Locator,
     stylist: &Stylist,
     indexer: &Indexer,
@@ -153,7 +157,7 @@ fn move_initialization(
     let default_edit = Edit::range_replacement("None".to_string(), default.range());
 
     // If the function is a stub, this is the only necessary edit.
-    if is_stub(function_def) {
+    if is_stub(function_def, semantic) {
         return Some(Fix::unsafe_edit(default_edit));
     }
 
@@ -213,8 +217,8 @@ fn move_initialization(
 /// Returns `true` if a function has an empty body, and is therefore a stub.
 ///
 /// A function body is considered to be empty if it contains only `pass` statements, `...` literals,
-/// and docstrings.
-fn is_stub(function_def: &ast::StmtFunctionDef) -> bool {
+/// `NotImplementedError` raises, or string literal statements (docstrings).
+fn is_stub(function_def: &ast::StmtFunctionDef, semantic: &SemanticModel) -> bool {
     function_def.body.iter().all(|stmt| match stmt {
         Stmt::Pass(_) => true,
         Stmt::Expr(ast::StmtExpr { value, range: _ }) => {
@@ -223,6 +227,15 @@ fn is_stub(function_def: &ast::StmtFunctionDef) -> bool {
                 Expr::StringLiteral(_) | Expr::EllipsisLiteral(_)
             )
         }
+        Stmt::Raise(StmtRaise {
+            range: _,
+            exc: exception,
+            cause: _,
+        }) => exception.as_ref().is_some_and(|exc| {
+            semantic
+                .resolve_builtin_symbol(map_callable(exc))
+                .is_some_and(|name| matches!(name, "NotImplementedError" | "NotImplemented"))
+        }),
         _ => false,
     })
 }

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B006_B006_8.py.snap

@@ -0,0 +1,92 @@
+---
+source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
+---
+B006_8.py:1:19: B006 [*] Do not use mutable data structures for argument defaults
+  |
+1 | def foo(a: list = []):
+  |                   ^^ B006
+2 |     raise NotImplementedError("")
+  |
+  = help: Replace with `None`; initialize within function
+
+ℹ Unsafe fix
+1   |-def foo(a: list = []):
+  1 |+def foo(a: list = None):
+2 2 |     raise NotImplementedError("")
+3 3 | 
+4 4 | 
+
+B006_8.py:5:19: B006 [*] Do not use mutable data structures for argument defaults
+  |
+5 | def bar(a: dict = {}):
+  |                   ^^ B006
+6 |     """ This one also has a docstring"""
+7 |     raise NotImplementedError("and has some text in here")
+  |
+  = help: Replace with `None`; initialize within function
+
+ℹ Unsafe fix
+2 2 |     raise NotImplementedError("")
+3 3 | 
+4 4 | 
+5   |-def bar(a: dict = {}):
+  5 |+def bar(a: dict = None):
+6 6 |     """ This one also has a docstring"""
+7 7 |     raise NotImplementedError("and has some text in here")
+8 8 | 
+
+B006_8.py:10:19: B006 [*] Do not use mutable data structures for argument defaults
+   |
+10 | def baz(a: list = []):
+   |                   ^^ B006
+11 |     """This one raises a different exception"""
+12 |     raise IndexError()
+   |
+   = help: Replace with `None`; initialize within function
+
+ℹ Unsafe fix
+7  7  |     raise NotImplementedError("and has some text in here")
+8  8  | 
+9  9  | 
+10    |-def baz(a: list = []):
+   10 |+def baz(a: list = None):
+11 11 |     """This one raises a different exception"""
+   12 |+    if a is None:
+   13 |+        a = []
+12 14 |     raise IndexError()
+13 15 | 
+14 16 | 
+
+B006_8.py:15:19: B006 [*] Do not use mutable data structures for argument defaults
+   |
+15 | def qux(a: list = []):
+   |                   ^^ B006
+16 |     raise NotImplementedError
+   |
+   = help: Replace with `None`; initialize within function
+
+ℹ Unsafe fix
+12 12 |     raise IndexError()
+13 13 | 
+14 14 | 
+15    |-def qux(a: list = []):
+   15 |+def qux(a: list = None):
+16 16 |     raise NotImplementedError
+17 17 | 
+18 18 | 
+
+B006_8.py:19:20: B006 [*] Do not use mutable data structures for argument defaults
+   |
+19 | def quux(a: list = []):
+   |                    ^^ B006
+20 |     raise NotImplemented
+   |
+   = help: Replace with `None`; initialize within function
+
+ℹ Unsafe fix
+16 16 |     raise NotImplementedError
+17 17 | 
+18 18 | 
+19    |-def quux(a: list = []):
+   19 |+def quux(a: list = None):
+20 20 |     raise NotImplemented