Implement E0117 (nonlocal-without-binding) (#1180)

resources/test/fixtures/pylint/nonlocal_without_binding.py

@@ -0,0 +1,19 @@
+nonlocal x
+
+
+def f():
+    nonlocal x
+
+
+def f():
+    nonlocal y
+
+
+def f():
+    x = 1
+
+    def f():
+        nonlocal x
+
+    def f():
+        nonlocal y

src/check_ast.rs

@@ -305,11 +305,23 @@ where
                     // Mark the binding in the defining scopes as used too. (Skip the global scope
                     // and the current scope.)
                     for name in names {
+                        let mut exists = false;
                         for index in self.scope_stack.iter().skip(1).rev().skip(1) {
                             if let Some(index) = self.scopes[*index].values.get(&name.as_str()) {
+                                exists = true;
                                 self.bindings[*index].used = usage;
                             }
                         }
+
+                        // Ensure that every nonlocal has an existing binding from a parent scope.
+                        if !exists {
+                            if self.settings.enabled.contains(&CheckCode::PLE0117) {
+                                self.add_check(Check::new(
+                                    CheckKind::NonlocalWithoutBinding(name.to_string()),
+                                    Range::from_located(stmt),
+                                ));
+                            }
+                        }
                     }
                 }
 

src/checks.rs

@@ -99,6 +99,7 @@ pub enum CheckCode {
     PLC0414,
     PLC2201,
     PLC3002,
+    PLE0117,
     PLE0118,
     PLE1142,
     PLR0206,
@@ -642,6 +643,7 @@ pub enum CheckKind {
     ConsiderUsingFromImport(String, String),
     GlobalVariableNotAssigned(String),
     MisplacedComparisonConstant(String),
+    NonlocalWithoutBinding(String),
     PropertyWithParameters,
     UnnecessaryDirectLambdaCall,
     UseSysExit(String),
@@ -954,6 +956,7 @@ impl CheckCode {
             CheckCode::PLC0414 => CheckKind::UselessImportAlias,
             CheckCode::PLC2201 => CheckKind::MisplacedComparisonConstant("...".to_string()),
             CheckCode::PLC3002 => CheckKind::UnnecessaryDirectLambdaCall,
+            CheckCode::PLE0117 => CheckKind::NonlocalWithoutBinding("...".to_string()),
             CheckCode::PLE0118 => CheckKind::UsedPriorGlobalDeclaration("...".to_string(), 1),
             CheckCode::PLE1142 => CheckKind::AwaitOutsideAsync,
             CheckCode::PLR0402 => {
@@ -1408,6 +1411,7 @@ impl CheckCode {
             CheckCode::PLC0414 => CheckCategory::Pylint,
             CheckCode::PLC2201 => CheckCategory::Pylint,
             CheckCode::PLC3002 => CheckCategory::Pylint,
+            CheckCode::PLE0117 => CheckCategory::Pylint,
             CheckCode::PLE0118 => CheckCategory::Pylint,
             CheckCode::PLE1142 => CheckCategory::Pylint,
             CheckCode::PLR0206 => CheckCategory::Pylint,
@@ -1546,6 +1550,7 @@ impl CheckKind {
             CheckKind::PropertyWithParameters => &CheckCode::PLR0206,
             CheckKind::UnnecessaryDirectLambdaCall => &CheckCode::PLC3002,
             CheckKind::UseSysExit(_) => &CheckCode::PLR1722,
+            CheckKind::NonlocalWithoutBinding(..) => &CheckCode::PLE0117,
             CheckKind::UsedPriorGlobalDeclaration(..) => &CheckCode::PLE0118,
             CheckKind::UselessElseOnLoop => &CheckCode::PLW0120,
             CheckKind::UselessImportAlias => &CheckCode::PLC0414,
@@ -1957,6 +1962,9 @@ impl CheckKind {
             CheckKind::MisplacedComparisonConstant(comparison) => {
                 format!("Comparison should be {comparison}")
             }
+            CheckKind::NonlocalWithoutBinding(name) => {
+                format!("Nonlocal name `{name}` found without binding")
+            }
             CheckKind::UnnecessaryDirectLambdaCall => "Lambda expression called directly. Execute \
                                                        the expression inline instead."
                 .to_string(),

src/checks_gen.rs

@@ -318,6 +318,7 @@ pub enum CheckCodePrefix {
     PLE0,
     PLE01,
     PLE011,
+    PLE0117,
     PLE0118,
     PLE1,
     PLE11,
@@ -1350,10 +1351,13 @@ impl CheckCodePrefix {
             CheckCodePrefix::PLC30 => vec![CheckCode::PLC3002],
             CheckCodePrefix::PLC300 => vec![CheckCode::PLC3002],
             CheckCodePrefix::PLC3002 => vec![CheckCode::PLC3002],
-            CheckCodePrefix::PLE => vec![CheckCode::PLE0118, CheckCode::PLE1142],
-            CheckCodePrefix::PLE0 => vec![CheckCode::PLE0118],
-            CheckCodePrefix::PLE01 => vec![CheckCode::PLE0118],
-            CheckCodePrefix::PLE011 => vec![CheckCode::PLE0118],
+            CheckCodePrefix::PLE => {
+                vec![CheckCode::PLE0117, CheckCode::PLE0118, CheckCode::PLE1142]
+            }
+            CheckCodePrefix::PLE0 => vec![CheckCode::PLE0117, CheckCode::PLE0118],
+            CheckCodePrefix::PLE01 => vec![CheckCode::PLE0117, CheckCode::PLE0118],
+            CheckCodePrefix::PLE011 => vec![CheckCode::PLE0117, CheckCode::PLE0118],
+            CheckCodePrefix::PLE0117 => vec![CheckCode::PLE0117],
             CheckCodePrefix::PLE0118 => vec![CheckCode::PLE0118],
             CheckCodePrefix::PLE1 => vec![CheckCode::PLE1142],
             CheckCodePrefix::PLE11 => vec![CheckCode::PLE1142],
@@ -2135,6 +2139,7 @@ impl CheckCodePrefix {
             CheckCodePrefix::PLE0 => SuffixLength::One,
             CheckCodePrefix::PLE01 => SuffixLength::Two,
             CheckCodePrefix::PLE011 => SuffixLength::Three,
+            CheckCodePrefix::PLE0117 => SuffixLength::Four,
             CheckCodePrefix::PLE0118 => SuffixLength::Four,
             CheckCodePrefix::PLE1 => SuffixLength::One,
             CheckCodePrefix::PLE11 => SuffixLength::Two,

src/pylint/mod.rs

@@ -14,6 +14,7 @@ mod tests {
     #[test_case(CheckCode::PLC0414, Path::new("import_aliasing.py"); "PLC0414")]
     #[test_case(CheckCode::PLC2201, Path::new("misplaced_comparison_constant.py"); "PLC2201")]
     #[test_case(CheckCode::PLC3002, Path::new("unnecessary_direct_lambda_call.py"); "PLC3002")]
+    #[test_case(CheckCode::PLE0117, Path::new("nonlocal_without_binding.py"); "PLE0117")]
     #[test_case(CheckCode::PLE0118, Path::new("used_prior_global_declaration.py"); "PLE0118")]
     #[test_case(CheckCode::PLE1142, Path::new("await_outside_async.py"); "PLE1142")]
     #[test_case(CheckCode::PLR0206, Path::new("property_with_parameters.py"); "PLR0206")]

src/pylint/snapshots/ruff__pylint__tests__PLE0117_nonlocal_without_binding.py.snap

@@ -0,0 +1,32 @@
+---
+source: src/pylint/mod.rs
+expression: checks
+---
+- kind:
+    NonlocalWithoutBinding: x
+  location:
+    row: 5
+    column: 4
+  end_location:
+    row: 5
+    column: 14
+  fix: ~
+- kind:
+    NonlocalWithoutBinding: y
+  location:
+    row: 9
+    column: 4
+  end_location:
+    row: 9
+    column: 14
+  fix: ~
+- kind:
+    NonlocalWithoutBinding: y
+  location:
+    row: 19
+    column: 8
+  end_location:
+    row: 19
+    column: 18
+  fix: ~
+