[pylint] Implement nonlocal-and-global (E115)

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

@@ -0,0 +1,67 @@
+# Positive cases
+
+counter = 0
+
+
+def count():
+    global counter
+    nonlocal counter
+    counter += 1
+
+
+def count():
+    counter = 0
+
+    def count(counter_type):
+        if counter_type == "nonlocal":
+            nonlocal counter
+            counter += 1
+        else:
+            global counter
+            counter += 1
+
+
+def count():
+    counter = 0
+
+    def count_twice():
+        for i in range(2):
+            nonlocal counter
+            counter += 1
+        global counter
+
+
+def count():
+    nonlocal counter
+    global counter
+    counter += 1
+
+
+# Negative cases
+
+counter = 0
+
+
+def count():
+    global counter
+    counter += 1
+
+
+def count():
+    counter = 0
+
+    def count_local():
+        nonlocal counter
+        counter += 1
+
+
+def count():
+    counter = 0
+
+    def count_local():
+        nonlocal counter
+        counter += 1
+
+    def count_global():
+        global counter
+        counter += 1

crates/ruff_linter/src/checkers/ast/analyze/statement.rs

@@ -30,7 +30,7 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
                 }));
             }
         }
-        Stmt::Nonlocal(ast::StmtNonlocal { names, range: _ }) => {
+        Stmt::Nonlocal(nonlocal @ ast::StmtNonlocal { names, range: _ }) => {
             if checker.enabled(Rule::AmbiguousVariableName) {
                 checker.diagnostics.extend(names.iter().filter_map(|name| {
                     pycodestyle::rules::ambiguous_variable_name(name, name.range())
@@ -50,6 +50,9 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
                     }
                 }
             }
+            if checker.enabled(Rule::NonlocalAndGlobal) {
+                pylint::rules::nonlocal_and_global(checker, nonlocal);
+            }
         }
         Stmt::Break(_) => {
             if checker.enabled(Rule::BreakOutsideLoop) {

crates/ruff_linter/src/codes.rs

@@ -234,6 +234,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pylint, "C3002") => (RuleGroup::Stable, rules::pylint::rules::UnnecessaryDirectLambdaCall),
         (Pylint, "E0100") => (RuleGroup::Stable, rules::pylint::rules::YieldInInit),
         (Pylint, "E0101") => (RuleGroup::Stable, rules::pylint::rules::ReturnInInit),
+        (Pylint, "E0115") => (RuleGroup::Preview, rules::pylint::rules::NonlocalAndGlobal),
         (Pylint, "E0116") => (RuleGroup::Stable, rules::pylint::rules::ContinueInFinally),
         (Pylint, "E0117") => (RuleGroup::Stable, rules::pylint::rules::NonlocalWithoutBinding),
         (Pylint, "E0118") => (RuleGroup::Stable, rules::pylint::rules::LoadBeforeGlobalDeclaration),

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

@@ -92,6 +92,7 @@ mod tests {
         Rule::NamedExprWithoutContext,
         Path::new("named_expr_without_context.py")
     )]
+    #[test_case(Rule::NonlocalAndGlobal, Path::new("nonlocal_and_global.py"))]
     #[test_case(Rule::NonlocalWithoutBinding, Path::new("nonlocal_without_binding.py"))]
     #[test_case(Rule::NonSlotAssignment, Path::new("non_slot_assignment.py"))]
     #[test_case(Rule::PropertyWithParameters, Path::new("property_with_parameters.py"))]

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

@@ -44,6 +44,7 @@ pub(crate) use no_self_use::*;
 pub(crate) use non_ascii_module_import::*;
 pub(crate) use non_ascii_name::*;
 pub(crate) use non_slot_assignment::*;
+pub(crate) use nonlocal_and_global::*;
 pub(crate) use nonlocal_without_binding::*;
 pub(crate) use potential_index_error::*;
 pub(crate) use property_with_parameters::*;
@@ -134,6 +135,7 @@ mod no_self_use;
 mod non_ascii_module_import;
 mod non_ascii_name;
 mod non_slot_assignment;
+mod nonlocal_and_global;
 mod nonlocal_without_binding;
 mod potential_index_error;
 mod property_with_parameters;

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

@@ -0,0 +1,70 @@
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast as ast;
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for variables which are both declared as both `nonlocal` and
+/// `global`.
+///
+/// ## Why is this bad?
+/// A `nonlocal` variable is a variable that is defined in the nearest
+/// enclosing scope, but not in the global scope, while a `global` variable is
+/// a variable that is defined in the global scope.
+///
+/// Declaring a variable as both `nonlocal` and `global` is contradictory and
+/// will raise a `SyntaxError`.
+///
+/// ## Example
+/// ```python
+/// counter = 0
+///
+///
+/// def increment():
+///     global counter
+///     nonlocal counter
+///     counter += 1
+/// ```
+///
+/// Use instead:
+/// ```python
+/// counter = 0
+///
+///
+/// def increment():
+///     global counter
+///     counter += 1
+/// ```
+///
+/// ## References
+/// - [Python documentation: The `global` statement](https://docs.python.org/3/reference/simple_stmts.html#the-global-statement)
+/// - [Python documentation: The `nonlocal` statement](https://docs.python.org/3/reference/simple_stmts.html#nonlocal)
+#[violation]
+pub struct NonlocalAndGlobal {
+    pub(crate) name: String,
+}
+
+impl Violation for NonlocalAndGlobal {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let NonlocalAndGlobal { name } = self;
+        format!("Name `{name}` is both `nonlocal` and `global`")
+    }
+}
+
+/// E115
+pub(crate) fn nonlocal_and_global(checker: &mut Checker, nonlocal: &ast::StmtNonlocal) {
+    // Determine whether any of the newly declared `nonlocal` variables are already declared as
+    // `global`.
+    for name in &nonlocal.names {
+        if let Some(global) = checker.semantic().global(name) {
+            checker.diagnostics.push(Diagnostic::new(
+                NonlocalAndGlobal {
+                    name: name.to_string(),
+                },
+                global,
+            ));
+        }
+    }
+}

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLE0115_nonlocal_and_global.py.snap

@@ -0,0 +1,37 @@
+---
+source: crates/ruff_linter/src/rules/pylint/mod.rs
+---
+nonlocal_and_global.py:7:12: PLE0115 Name `counter` is both `nonlocal` and `global`
+  |
+6 | def count():
+7 |     global counter
+  |            ^^^^^^^ PLE0115
+8 |     nonlocal counter
+9 |     counter += 1
+  |
+
+nonlocal_and_global.py:20:20: PLE0115 Name `counter` is both `nonlocal` and `global`
+   |
+18 |             counter += 1
+19 |         else:
+20 |             global counter
+   |                    ^^^^^^^ PLE0115
+21 |             counter += 1
+   |
+
+nonlocal_and_global.py:31:16: PLE0115 Name `counter` is both `nonlocal` and `global`
+   |
+29 |             nonlocal counter
+30 |             counter += 1
+31 |         global counter
+   |                ^^^^^^^ PLE0115
+   |
+
+nonlocal_and_global.py:36:12: PLE0115 Name `counter` is both `nonlocal` and `global`
+   |
+34 | def count():
+35 |     nonlocal counter
+36 |     global counter
+   |            ^^^^^^^ PLE0115
+37 |     counter += 1
+   |