[pylint] Detect subclasses of builtin exceptions (PLW0133)

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

@@ -2,15 +2,40 @@
 from contextlib import suppress
 
 
+class MyError(Exception):
+    ...
+
+
+class MySubError(MyError):
+    ...
+
+
+class MyValueError(ValueError):
+    ...
+
+
+class MyUserWarning(UserWarning):
+    ...
+
+
+# Violation test cases with builtin errors: PLW0133
+
+
 # Test case 1: Useless exception statement
 def func():
     AssertionError("This is an assertion error")  # PLW0133
+    MyError("This is a custom error")  # PLW0133
+    MySubError("This is a custom error")  # PLW0133
+    MyValueError("This is a custom value error")  # PLW0133
 
 
 # Test case 2: Useless exception statement in try-except block
 def func():
     try:
         Exception("This is an exception")  # PLW0133
+        MyError("This is an exception")  # PLW0133
+        MySubError("This is an exception")  # PLW0133
+        MyValueError("This is an exception")  # PLW0133
     except Exception as err:
         pass
 
@@ -19,19 +44,28 @@ def func():
 def func():
     if True:
         RuntimeError("This is an exception")  # PLW0133
+        MyError("This is an exception")  # PLW0133
+        MySubError("This is an exception")  # PLW0133
+        MyValueError("This is an exception")  # PLW0133
 
 
 # Test case 4: Useless exception statement in class
 def func():
     class Class:
         def __init__(self):
             TypeError("This is an exception")  # PLW0133
+            MyError("This is an exception")  # PLW0133
+            MySubError("This is an exception")  # PLW0133
+            MyValueError("This is an exception")  # PLW0133
 
 
 # Test case 5: Useless exception statement in function
 def func():
     def inner():
         IndexError("This is an exception")  # PLW0133
+        MyError("This is an exception")  # PLW0133
+        MySubError("This is an exception")  # PLW0133
+        MyValueError("This is an exception")  # PLW0133
 
     inner()
 
@@ -40,6 +74,9 @@ def inner():
 def func():
     while True:
         KeyError("This is an exception")  # PLW0133
+        MyError("This is an exception")  # PLW0133
+        MySubError("This is an exception")  # PLW0133
+        MyValueError("This is an exception")  # PLW0133
 
 
 # Test case 7: Useless exception statement in abstract class
@@ -48,27 +85,58 @@ class Class(ABC):
         @abstractmethod
         def method(self):
             NotImplementedError("This is an exception")  # PLW0133
+            MyError("This is an exception")  # PLW0133
+            MySubError("This is an exception")  # PLW0133
+            MyValueError("This is an exception")  # PLW0133
 
 
 # Test case 8: Useless exception statement inside context manager
 def func():
-    with suppress(AttributeError):
+    with suppress(Exception):
         AttributeError("This is an exception")  # PLW0133
+        MyError("This is an exception")  # PLW0133
+        MySubError("This is an exception")  # PLW0133
+        MyValueError("This is an exception")  # PLW0133
 
 
 # Test case 9: Useless exception statement in parentheses
 def func():
     (RuntimeError("This is an exception"))  # PLW0133
+    (MyError("This is an exception"))  # PLW0133
+    (MySubError("This is an exception"))  # PLW0133
+    (MyValueError("This is an exception"))  # PLW0133
 
 
 # Test case 10: Useless exception statement in continuation
 def func():
     x = 1; (RuntimeError("This is an exception")); y = 2  # PLW0133
+    x = 1; (MyError("This is an exception")); y = 2  # PLW0133
+    x = 1; (MySubError("This is an exception")); y = 2  # PLW0133
+    x = 1; (MyValueError("This is an exception")); y = 2  # PLW0133
 
 
 # Test case 11: Useless warning statement
 def func():
-    UserWarning("This is an assertion error")  # PLW0133
+    UserWarning("This is a user warning")  # PLW0133
+    MyUserWarning("This is a custom user warning")  # PLW0133
+
+
+# Test case 12: Useless exception statement at module level
+import builtins
+
+builtins.TypeError("still an exception even though it's an Attribute")  # PLW0133
+
+PythonFinalizationError("Added in Python 3.13")  # PLW0133
+
+MyError("This is an exception")  # PLW0133
+
+MySubError("This is an exception")  # PLW0133
+
+MyValueError("This is an exception")  # PLW0133
+
+UserWarning("This is a user warning")  # PLW0133
+
+MyUserWarning("This is a custom user warning")  # PLW0133
 
 
 # Non-violation test cases: PLW0133
@@ -119,10 +187,3 @@ def func():
 def func():
     with suppress(AttributeError):
         raise AttributeError("This is an exception")  # OK
-
-
-import builtins
-
-builtins.TypeError("still an exception even though it's an Attribute")
-
-PythonFinalizationError("Added in Python 3.13")

crates/ruff_linter/src/preview.rs

@@ -9,6 +9,11 @@ use crate::settings::LinterSettings;
 
 // Rule-specific behavior
 
+// https://github.com/astral-sh/ruff/pull/21382
+pub(crate) const fn is_custom_exception_checking_enabled(settings: &LinterSettings) -> bool {
+    settings.preview.is_enabled()
+}
+
 // https://github.com/astral-sh/ruff/pull/15541
 pub(crate) const fn is_suspicious_function_reference_enabled(settings: &LinterSettings) -> bool {
     settings.preview.is_enabled()

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

@@ -16,10 +16,10 @@ mod tests {
     use crate::registry::Rule;
     use crate::rules::{flake8_tidy_imports, pylint};
 
-    use crate::assert_diagnostics;
     use crate::settings::LinterSettings;
     use crate::settings::types::PreviewMode;
     use crate::test::test_path;
+    use crate::{assert_diagnostics, assert_diagnostics_diff};
 
     #[test_case(Rule::SingledispatchMethod, Path::new("singledispatch_method.py"))]
     #[test_case(
@@ -253,6 +253,32 @@ mod tests {
         Ok(())
     }
 
+    #[test_case(
+        Rule::UselessExceptionStatement,
+        Path::new("useless_exception_statement.py")
+    )]
+    fn preview_rules(rule_code: Rule, path: &Path) -> Result<()> {
+        let snapshot = format!(
+            "preview__{}_{}",
+            rule_code.noqa_code(),
+            path.to_string_lossy()
+        );
+
+        assert_diagnostics_diff!(
+            snapshot,
+            Path::new("pylint").join(path).as_path(),
+            &LinterSettings {
+                preview: PreviewMode::Disabled,
+                ..LinterSettings::for_rule(rule_code)
+            },
+            &LinterSettings {
+                preview: PreviewMode::Enabled,
+                ..LinterSettings::for_rule(rule_code)
+            }
+        );
+        Ok(())
+    }
+
     #[test]
     fn continue_in_finally() -> Result<()> {
         let diagnostics = test_path(

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

@@ -1,10 +1,11 @@
 use ruff_macros::{ViolationMetadata, derive_message_formats};
 use ruff_python_ast::{self as ast, Expr};
-use ruff_python_semantic::SemanticModel;
+use ruff_python_semantic::{SemanticModel, analyze};
 use ruff_python_stdlib::builtins;
 use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
+use crate::preview::is_custom_exception_checking_enabled;
 use crate::{Edit, Fix, FixAvailability, Violation};
 use ruff_python_ast::PythonVersion;
 
@@ -20,6 +21,9 @@ use ruff_python_ast::PythonVersion;
 /// This rule only detects built-in exceptions, like `ValueError`, and does
 /// not catch user-defined exceptions.
 ///
+/// In [preview], this rule will also detect user-defined exceptions, but only
+/// the ones defined in the file being checked.
+///
 /// ## Example
 /// ```python
 /// ValueError("...")
@@ -32,7 +36,8 @@ use ruff_python_ast::PythonVersion;
 ///
 /// ## Fix safety
 /// This rule's fix is marked as unsafe, as converting a useless exception
-/// statement to a `raise` statement will change the program's behavior.
+///
+/// [preview]: https://docs.astral.sh/ruff/preview/
 #[derive(ViolationMetadata)]
 #[violation_metadata(stable_since = "0.5.0")]
 pub(crate) struct UselessExceptionStatement;
@@ -56,7 +61,10 @@ pub(crate) fn useless_exception_statement(checker: &Checker, expr: &ast::StmtExp
         return;
     };
 
-    if is_builtin_exception(func, checker.semantic(), checker.target_version()) {
+    if is_builtin_exception(func, checker.semantic(), checker.target_version())
+        || (is_custom_exception_checking_enabled(checker.settings())
+            && is_custom_exception(func, checker.semantic(), checker.target_version()))
+    {
         let mut diagnostic = checker.report_diagnostic(UselessExceptionStatement, expr.range());
         diagnostic.set_fix(Fix::unsafe_edit(Edit::insertion(
             "raise ".to_string(),
@@ -78,3 +86,34 @@ fn is_builtin_exception(
             if builtins::is_exception(name, target_version.minor))
         })
 }
+
+/// Returns `true` if the given expression is a custom exception.
+fn is_custom_exception(
+    expr: &Expr,
+    semantic: &SemanticModel,
+    target_version: PythonVersion,
+) -> bool {
+    let Some(qualified_name) = semantic.resolve_qualified_name(expr) else {
+        return false;
+    };
+    let Some(symbol) = qualified_name.segments().last() else {
+        return false;
+    };
+    let Some(binding_id) = semantic.lookup_symbol(symbol) else {
+        return false;
+    };
+    let binding = semantic.binding(binding_id);
+    let Some(source) = binding.source else {
+        return false;
+    };
+    let statement = semantic.statement(source);
+    if let ast::Stmt::ClassDef(class_def) = statement {
+        return analyze::class::any_qualified_base_class(class_def, semantic, &|qualified_name| {
+            if let ["" | "builtins", name] = qualified_name.segments() {
+                return builtins::is_exception(name, target_version.minor);
+            }
+            false
+        });
+    }
+    false
+}