[pylint] Implement import-self (W0406) (#4154)

crates/ruff/resources/test/fixtures/pylint/import_self/module.py

@@ -0,0 +1,3 @@
+import import_self.module
+from import_self import module
+from . import module

crates/ruff/src/checkers/ast/mod.rs

@@ -1000,6 +1000,13 @@ where
                     if self.settings.rules.enabled(Rule::ManualFromImport) {
                         pylint::rules::manual_from_import(self, stmt, alias, names);
                     }
+                    if self.settings.rules.enabled(Rule::ImportSelf) {
+                        if let Some(diagnostic) =
+                            pylint::rules::import_self(alias, self.module_path.as_deref())
+                        {
+                            self.diagnostics.push(diagnostic);
+                        }
+                    }
 
                     if let Some(asname) = &alias.node.asname {
                         let name = alias.node.name.split('.').last().unwrap();
@@ -1477,6 +1484,17 @@ where
                     }
                 }
 
+                if self.settings.rules.enabled(Rule::ImportSelf) {
+                    if let Some(diagnostic) = pylint::rules::import_from_self(
+                        *level,
+                        module.as_deref(),
+                        names,
+                        self.module_path.as_deref(),
+                    ) {
+                        self.diagnostics.push(diagnostic);
+                    }
+                }
+
                 if self.settings.rules.enabled(Rule::BannedImportFrom) {
                     if let Some(diagnostic) = flake8_import_conventions::rules::banned_import_from(
                         stmt,

crates/ruff/src/codes.rs

@@ -204,6 +204,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<Rule> {
         (Pylint, "R5501") => Rule::CollapsibleElseIf,
         (Pylint, "W0120") => Rule::UselessElseOnLoop,
         (Pylint, "W0129") => Rule::AssertOnStringLiteral,
+        (Pylint, "W0406") => Rule::ImportSelf,
         (Pylint, "W0602") => Rule::GlobalVariableNotAssigned,
         (Pylint, "W0603") => Rule::GlobalStatement,
         (Pylint, "W0711") => Rule::BinaryOpException,

crates/ruff/src/registry.rs

@@ -156,6 +156,7 @@ ruff_macros::register_rules!(
     rules::pylint::rules::BadStringFormatType,
     rules::pylint::rules::BidirectionalUnicode,
     rules::pylint::rules::BinaryOpException,
+    rules::pylint::rules::ImportSelf,
     rules::pylint::rules::InvalidCharacterBackspace,
     rules::pylint::rules::InvalidCharacterSub,
     rules::pylint::rules::InvalidCharacterEsc,

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

@@ -40,6 +40,7 @@ mod tests {
     #[test_case(Rule::ContinueInFinally, Path::new("continue_in_finally.py"); "PLE0116")]
     #[test_case(Rule::GlobalStatement, Path::new("global_statement.py"); "PLW0603")]
     #[test_case(Rule::GlobalVariableNotAssigned, Path::new("global_variable_not_assigned.py"); "PLW0602")]
+    #[test_case(Rule::ImportSelf, Path::new("import_self/module.py"); "PLW0406")]
     #[test_case(Rule::InvalidAllFormat, Path::new("invalid_all_format.py"); "PLE0605")]
     #[test_case(Rule::InvalidAllObject, Path::new("invalid_all_object.py"); "PLE0604")]
     #[test_case(Rule::InvalidCharacterBackspace, Path::new("invalid_characters.py"); "PLE2510")]

crates/ruff/src/rules/pylint/rules/import_self.rs

@@ -0,0 +1,70 @@
+use rustpython_parser::ast::Alias;
+
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::helpers::resolve_imported_module_path;
+
+#[violation]
+pub struct ImportSelf {
+    pub name: String,
+}
+
+impl Violation for ImportSelf {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let Self { name } = self;
+        format!("Module `{name}` imports itself")
+    }
+}
+
+/// PLW0406
+pub fn import_self(alias: &Alias, module_path: Option<&[String]>) -> Option<Diagnostic> {
+    let Some(module_path) = module_path else {
+        return None;
+    };
+
+    if alias.node.name.split('.').eq(module_path) {
+        return Some(Diagnostic::new(
+            ImportSelf {
+                name: alias.node.name.clone(),
+            },
+            alias.range(),
+        ));
+    }
+
+    None
+}
+
+/// PLW0406
+pub fn import_from_self(
+    level: Option<usize>,
+    module: Option<&str>,
+    names: &[Alias],
+    module_path: Option<&[String]>,
+) -> Option<Diagnostic> {
+    let Some(module_path) = module_path else {
+        return None;
+    };
+    let Some(imported_module_path) = resolve_imported_module_path(level, module, Some(module_path)) else {
+        return None;
+    };
+
+    if imported_module_path
+        .split('.')
+        .eq(&module_path[..module_path.len() - 1])
+    {
+        if let Some(alias) = names
+            .iter()
+            .find(|alias| alias.node.name == module_path[module_path.len() - 1])
+        {
+            return Some(Diagnostic::new(
+                ImportSelf {
+                    name: format!("{}.{}", imported_module_path, alias.node.name),
+                },
+                alias.range(),
+            ));
+        }
+    }
+
+    None
+}

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

@@ -10,6 +10,7 @@ pub use comparison_of_constant::{comparison_of_constant, ComparisonOfConstant};
 pub use continue_in_finally::{continue_in_finally, ContinueInFinally};
 pub use global_statement::{global_statement, GlobalStatement};
 pub use global_variable_not_assigned::GlobalVariableNotAssigned;
+pub use import_self::{import_from_self, import_self, ImportSelf};
 pub use invalid_all_format::{invalid_all_format, InvalidAllFormat};
 pub use invalid_all_object::{invalid_all_object, InvalidAllObject};
 pub use invalid_envvar_default::{invalid_envvar_default, InvalidEnvvarDefault};
@@ -57,6 +58,7 @@ mod comparison_of_constant;
 mod continue_in_finally;
 mod global_statement;
 mod global_variable_not_assigned;
+mod import_self;
 mod invalid_all_format;
 mod invalid_all_object;
 mod invalid_envvar_default;

crates/ruff/src/rules/pylint/snapshots/ruff__rules__pylint__tests__PLW0406_import_self__module.py.snap

@@ -0,0 +1,28 @@
+---
+source: crates/ruff/src/rules/pylint/mod.rs
+---
+module.py:1:8: PLW0406 Module `import_self.module` imports itself
+  |
+1 | import import_self.module
+  |        ^^^^^^^^^^^^^^^^^^ PLW0406
+2 | from import_self import module
+3 | from . import module
+  |
+
+module.py:2:25: PLW0406 Module `import_self.module` imports itself
+  |
+2 | import import_self.module
+3 | from import_self import module
+  |                         ^^^^^^ PLW0406
+4 | from . import module
+  |
+
+module.py:3:15: PLW0406 Module `import_self.module` imports itself
+  |
+3 | import import_self.module
+4 | from import_self import module
+5 | from . import module
+  |               ^^^^^^ PLW0406
+  |
+
+