Implement B016 (#595)

README.md

@@ -469,6 +469,7 @@ The 🛠 emoji indicates that a rule is automatically fixable by the `--fix` com
 | B013 | RedundantTupleInExceptionHandler | A length-one tuple literal is redundant. Write `except ValueError:` instead of `except (ValueError,):`. |  |
 | B014 | DuplicateHandlerException | Exception handler with duplicate exception: `ValueError` | 🛠 |
 | B015 | UselessComparison | Pointless comparison. This comparison does nothing but waste CPU instructions. Either prepend `assert` or remove it. |  |
+| B016 | CannotRaiseLiteral | Cannot raise a literal. Did you intend to return it or raise an Exception? |  |
 | B017 | NoAssertRaisesException | `assertRaises(Exception):` should be considered evil. |  |
 | B018 | UselessExpression | Found useless expression. Either assign it to a variable or remove it. |  |
 | B025 | DuplicateTryBlockException | try-except block with duplicate exception `Exception` |  |

resources/test/fixtures/B016.py

@@ -0,0 +1,11 @@
+"""
+Should emit:
+B016 - on lines 6, 7, and 8
+"""
+
+raise False
+raise 1
+raise "string"
+raise Exception(False)
+raise Exception(1)
+raise Exception("string")

src/check_ast.rs

@@ -733,6 +733,11 @@ where
                         pyflakes::plugins::raise_not_implemented(self, expr);
                     }
                 }
+                if self.settings.enabled.contains(&CheckCode::B016) {
+                    if let Some(exc) = exc {
+                        flake8_bugbear::plugins::cannot_raise_literal(self, exc);
+                    }
+                }
             }
             StmtKind::AugAssign { target, .. } => {
                 self.handle_node_load(target);

src/checks.rs

@@ -85,6 +85,7 @@ pub enum CheckCode {
     B013,
     B014,
     B015,
+    B016,
     B017,
     B018,
     B025,
@@ -303,6 +304,7 @@ pub enum CheckKind {
     RedundantTupleInExceptionHandler(String),
     DuplicateHandlerException(Vec<String>),
     UselessComparison,
+    CannotRaiseLiteral,
     NoAssertRaisesException,
     UselessExpression,
     DuplicateTryBlockException(String),
@@ -493,6 +495,7 @@ impl CheckCode {
             }
             CheckCode::B014 => CheckKind::DuplicateHandlerException(vec!["ValueError".to_string()]),
             CheckCode::B015 => CheckKind::UselessComparison,
+            CheckCode::B016 => CheckKind::CannotRaiseLiteral,
             CheckCode::B017 => CheckKind::NoAssertRaisesException,
             CheckCode::B018 => CheckKind::UselessExpression,
             CheckCode::B025 => CheckKind::DuplicateTryBlockException("Exception".to_string()),
@@ -688,6 +691,7 @@ impl CheckCode {
             CheckCode::B013 => CheckCategory::Flake8Bugbear,
             CheckCode::B014 => CheckCategory::Flake8Bugbear,
             CheckCode::B015 => CheckCategory::Flake8Bugbear,
+            CheckCode::B016 => CheckCategory::Flake8Bugbear,
             CheckCode::B017 => CheckCategory::Flake8Bugbear,
             CheckCode::B018 => CheckCategory::Flake8Bugbear,
             CheckCode::B025 => CheckCategory::Flake8Bugbear,
@@ -850,6 +854,7 @@ impl CheckKind {
             CheckKind::RedundantTupleInExceptionHandler(_) => &CheckCode::B013,
             CheckKind::DuplicateHandlerException(_) => &CheckCode::B014,
             CheckKind::UselessComparison => &CheckCode::B015,
+            CheckKind::CannotRaiseLiteral => &CheckCode::B016,
             CheckKind::NoAssertRaisesException => &CheckCode::B017,
             CheckKind::UselessExpression => &CheckCode::B018,
             CheckKind::DuplicateTryBlockException(_) => &CheckCode::B025,
@@ -1134,6 +1139,9 @@ impl CheckKind {
                                              but waste CPU instructions. Either prepend `assert` \
                                              or remove it."
                 .to_string(),
+            CheckKind::CannotRaiseLiteral => "Cannot raise a literal. Did you intend to return it \
+                                              or raise an Exception?"
+                .to_string(),
             CheckKind::DuplicateHandlerException(names) => {
                 if names.len() == 1 {
                     let name = &names[0];

src/checks_gen.rs

@@ -25,6 +25,7 @@ pub enum CheckCodePrefix {
     B013,
     B014,
     B015,
+    B016,
     B017,
     B018,
     B02,
@@ -263,6 +264,7 @@ impl CheckCodePrefix {
                 CheckCode::B013,
                 CheckCode::B014,
                 CheckCode::B015,
+                CheckCode::B016,
                 CheckCode::B017,
                 CheckCode::B018,
                 CheckCode::B025,
@@ -276,6 +278,7 @@ impl CheckCodePrefix {
                 CheckCode::B013,
                 CheckCode::B014,
                 CheckCode::B015,
+                CheckCode::B016,
                 CheckCode::B017,
                 CheckCode::B018,
                 CheckCode::B025,
@@ -290,6 +293,7 @@ impl CheckCodePrefix {
                 CheckCode::B013,
                 CheckCode::B014,
                 CheckCode::B015,
+                CheckCode::B016,
                 CheckCode::B017,
                 CheckCode::B018,
             ],
@@ -297,6 +301,7 @@ impl CheckCodePrefix {
             CheckCodePrefix::B013 => vec![CheckCode::B013],
             CheckCodePrefix::B014 => vec![CheckCode::B014],
             CheckCodePrefix::B015 => vec![CheckCode::B015],
+            CheckCodePrefix::B016 => vec![CheckCode::B016],
             CheckCodePrefix::B017 => vec![CheckCode::B017],
             CheckCodePrefix::B018 => vec![CheckCode::B018],
             CheckCodePrefix::B02 => vec![CheckCode::B025],
@@ -923,6 +928,7 @@ impl CheckCodePrefix {
             CheckCodePrefix::B013 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B014 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B015 => PrefixSpecificity::Explicit,
+            CheckCodePrefix::B016 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B017 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B018 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B02 => PrefixSpecificity::Tens,

src/flake8_bugbear/plugins/cannot_raise_literal.rs

@@ -0,0 +1,15 @@
+use rustpython_ast::{Expr, ExprKind};
+
+use crate::ast::types::{CheckLocator, Range};
+use crate::check_ast::Checker;
+use crate::checks::{Check, CheckKind};
+
+/// B016
+pub fn cannot_raise_literal(checker: &mut Checker, expr: &Expr) {
+    if let ExprKind::Constant { .. } = &expr.node {
+        checker.add_check(Check::new(
+            CheckKind::CannotRaiseLiteral,
+            checker.locate_check(Range::from_located(expr)),
+        ));
+    }
+}

src/flake8_bugbear/plugins/mod.rs

@@ -1,5 +1,6 @@
 pub use assert_false::assert_false;
 pub use assert_raises_exception::assert_raises_exception;
+pub use cannot_raise_literal::cannot_raise_literal;
 pub use duplicate_exceptions::{duplicate_exceptions, duplicate_handler_exceptions};
 pub use function_call_argument_default::function_call_argument_default;
 pub use mutable_argument_default::mutable_argument_default;
@@ -11,6 +12,7 @@ pub use useless_expression::useless_expression;
 
 mod assert_false;
 mod assert_raises_exception;
+mod cannot_raise_literal;
 mod duplicate_exceptions;
 mod function_call_argument_default;
 mod mutable_argument_default;

src/linter.rs

@@ -300,6 +300,7 @@ mod tests {
     #[test_case(CheckCode::B013, Path::new("B013.py"); "B013")]
     #[test_case(CheckCode::B014, Path::new("B014.py"); "B014")]
     #[test_case(CheckCode::B015, Path::new("B015.py"); "B015")]
+    #[test_case(CheckCode::B016, Path::new("B016.py"); "B016")]
     #[test_case(CheckCode::B017, Path::new("B017.py"); "B017")]
     #[test_case(CheckCode::B018, Path::new("B018.py"); "B018")]
     #[test_case(CheckCode::B025, Path::new("B025.py"); "B025")]

src/snapshots/ruff__linter__tests__B016_B016.py.snap

@@ -0,0 +1,29 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: CannotRaiseLiteral
+  location:
+    row: 6
+    column: 6
+  end_location:
+    row: 6
+    column: 11
+  fix: ~
+- kind: CannotRaiseLiteral
+  location:
+    row: 7
+    column: 6
+  end_location:
+    row: 7
+    column: 7
+  fix: ~
+- kind: CannotRaiseLiteral
+  location:
+    row: 8
+    column: 6
+  end_location:
+    row: 8
+    column: 14
+  fix: ~
+