[pylint] - implement global-at-module-level (W0604)

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

@@ -0,0 +1,10 @@
+global price  # W0604
+
+price = 25
+
+if True:
+    global X  # W0604
+
+def no_error():
+    global price
+    price = 30

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

@@ -21,6 +21,9 @@ use crate::settings::types::PythonVersion;
 pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
     match stmt {
         Stmt::Global(ast::StmtGlobal { names, range: _ }) => {
+            if checker.enabled(Rule::GlobalAtModuleLevel) {
+                pylint::rules::global_at_module_level(checker, stmt);
+            }
             if checker.enabled(Rule::AmbiguousVariableName) {
                 checker.diagnostics.extend(names.iter().filter_map(|name| {
                     pycodestyle::rules::ambiguous_variable_name(name, name.range())

crates/ruff_linter/src/codes.rs

@@ -264,6 +264,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pylint, "W0131") => (RuleGroup::Stable, rules::pylint::rules::NamedExprWithoutContext),
         (Pylint, "W0406") => (RuleGroup::Stable, rules::pylint::rules::ImportSelf),
         (Pylint, "W0602") => (RuleGroup::Stable, rules::pylint::rules::GlobalVariableNotAssigned),
+        (Pylint, "W0604") => (RuleGroup::Preview, rules::pylint::rules::GlobalAtModuleLevel),
         (Pylint, "W0603") => (RuleGroup::Stable, rules::pylint::rules::GlobalStatement),
         (Pylint, "W0711") => (RuleGroup::Stable, rules::pylint::rules::BinaryOpException),
         (Pylint, "W1508") => (RuleGroup::Stable, rules::pylint::rules::InvalidEnvvarDefault),

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

@@ -138,6 +138,7 @@ mod tests {
     #[test_case(Rule::NoSelfUse, Path::new("no_self_use.py"))]
     #[test_case(Rule::MisplacedBareRaise, Path::new("misplaced_bare_raise.py"))]
     #[test_case(Rule::LiteralMembership, Path::new("literal_membership.py"))]
+    #[test_case(Rule::GlobalAtModuleLevel, Path::new("global_at_module_level.py"))]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());
         let diagnostics = test_path(

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

@@ -0,0 +1,34 @@
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::Stmt;
+use ruff_text_size::Ranged;
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for uses of the `global` keyword at the module level.
+///
+/// ## Why is this bad?
+/// The `global` keyword is used within functions to indicate that a name
+/// refers to a global variable, rather than a local variable.
+///
+/// At the module level, all names are global by default, so the `global`
+/// keyword is redundant.
+#[violation]
+pub struct GlobalAtModuleLevel;
+
+impl Violation for GlobalAtModuleLevel {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("`global` at module level is redundant")
+    }
+}
+
+/// PLW0604
+pub(crate) fn global_at_module_level(checker: &mut Checker, stmt: &Stmt) {
+    if checker.semantic().current_scope().kind.is_module() {
+        checker
+            .diagnostics
+            .push(Diagnostic::new(GlobalAtModuleLevel, stmt.range()));
+    }
+}

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

@@ -14,6 +14,7 @@ pub(crate) use comparison_with_itself::*;
 pub(crate) use continue_in_finally::*;
 pub(crate) use duplicate_bases::*;
 pub(crate) use eq_without_hash::*;
+pub(crate) use global_at_module_level::*;
 pub(crate) use global_statement::*;
 pub(crate) use global_variable_not_assigned::*;
 pub(crate) use import_self::*;
@@ -78,6 +79,7 @@ mod comparison_with_itself;
 mod continue_in_finally;
 mod duplicate_bases;
 mod eq_without_hash;
+mod global_at_module_level;
 mod global_statement;
 mod global_variable_not_assigned;
 mod import_self;

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLW0604_global_at_module_level.py.snap

@@ -0,0 +1,21 @@
+---
+source: crates/ruff_linter/src/rules/pylint/mod.rs
+---
+global_at_module_level.py:1:1: PLW0604 `global` at module level is redundant
+  |
+1 | global price  # W0604
+  | ^^^^^^^^^^^^ PLW0604
+2 | 
+3 | price = 25
+  |
+
+global_at_module_level.py:6:5: PLW0604 `global` at module level is redundant
+  |
+5 | if True:
+6 |     global X  # W0604
+  |     ^^^^^^^^ PLW0604
+7 | 
+8 | def no_error():
+  |
+
+