Implement unnecessary-direct-lambda-call (#1008)

Author: harupy

README.md

@@ -751,8 +751,9 @@ For more, see [Pylint](https://pypi.org/project/pylint/2.15.7/) on PyPI.
 
 | Code | Name | Message | Fix |
 | ---- | ---- | ------- | --- |
-| PLE1142 | AwaitOutsideAsync | `await` should be used within an async function |  |
+| PLC3002 | UnnecessaryDirectLambdaCall | Lambda expression called directly. Execute the expression inline instead. |  |
 | PLR0206 | PropertyWithParameters | Cannot have defined parameters for properties |  |
+| PLE1142 | AwaitOutsideAsync | `await` should be used within an async function |  |
 
 ### Ruff-specific rules
 

resources/test/fixtures/pylint/unnecessary_direct_lambda_call.py

@@ -0,0 +1,5 @@
+"""Test unnecessary direct calls to lambda expressions."""
+# pylint: disable=undefined-variable, line-too-long
+
+y = (lambda x: x**2 + 2*x + 1)(a)  # [unnecessary-direct-lambda-call]
+y = max((lambda x: x**2)(a), (lambda x: x+1)(a))  # [unnecessary-direct-lambda-call,unnecessary-direct-lambda-call]

src/check_ast.rs

@@ -442,7 +442,7 @@ where
                 }
 
                 if self.settings.enabled.contains(&CheckCode::PLR0206) {
-                    pylint::plugins::property_with_parameters(self, stmt, decorator_list, args)
+                    pylint::plugins::property_with_parameters(self, stmt, decorator_list, args);
                 }
 
                 self.check_builtin_shadowing(name, Range::from_located(stmt), true);
@@ -1712,6 +1712,11 @@ where
                     pygrep_hooks::checks::no_eval(self, func);
                 }
 
+                // pylint
+                if self.settings.enabled.contains(&CheckCode::PLC3002) {
+                    pylint::plugins::unnecessary_direct_lambda_call(self, expr, func);
+                }
+
                 // Ruff
                 if self.settings.enabled.contains(&CheckCode::RUF101) {
                     rules::plugins::convert_exit_to_sys_exit(self, func);

src/checks.rs

@@ -91,6 +91,7 @@ pub enum CheckCode {
     F841,
     F901,
     // pylint errors
+    PLC3002,
     PLR0206,
     PLE1142,
     // flake8-builtins
@@ -541,6 +542,7 @@ pub enum CheckKind {
     UnusedVariable(String),
     YieldOutsideFunction(DeferralKeyword),
     // pylint errors
+    UnnecessaryDirectLambdaCall,
     PropertyWithParameters,
     AwaitOutsideAsync,
     // flake8-builtins
@@ -827,6 +829,7 @@ impl CheckCode {
             CheckCode::F841 => CheckKind::UnusedVariable("...".to_string()),
             CheckCode::F901 => CheckKind::RaiseNotImplemented,
             // pylint errors
+            CheckCode::PLC3002 => CheckKind::UnnecessaryDirectLambdaCall,
             CheckCode::PLR0206 => CheckKind::PropertyWithParameters,
             CheckCode::PLE1142 => CheckKind::AwaitOutsideAsync,
             // flake8-builtins
@@ -1240,6 +1243,7 @@ impl CheckCode {
             CheckCode::N817 => CheckCategory::PEP8Naming,
             CheckCode::N818 => CheckCategory::PEP8Naming,
             CheckCode::PGH001 => CheckCategory::PygrepHooks,
+            CheckCode::PLC3002 => CheckCategory::Pylint,
             CheckCode::PLR0206 => CheckCategory::Pylint,
             CheckCode::PLE1142 => CheckCategory::Pylint,
             CheckCode::Q000 => CheckCategory::Flake8Quotes,
@@ -1354,6 +1358,7 @@ impl CheckKind {
             CheckKind::NoNewLineAtEndOfFile => &CheckCode::W292,
             CheckKind::InvalidEscapeSequence(_) => &CheckCode::W605,
             // pylint errors
+            CheckKind::UnnecessaryDirectLambdaCall => &CheckCode::PLC3002,
             CheckKind::PropertyWithParameters => &CheckCode::PLR0206,
             CheckKind::AwaitOutsideAsync => &CheckCode::PLE1142,
             // flake8-builtins
@@ -1728,6 +1733,9 @@ impl CheckKind {
                 format!("Invalid escape sequence: '\\{char}'")
             }
             // pylint errors
+            CheckKind::UnnecessaryDirectLambdaCall => "Lambda expression called directly. Execute \
+                                                       the expression inline instead."
+                .to_string(),
             CheckKind::PropertyWithParameters => {
                 "Cannot have defined parameters for properties".to_string()
             }

src/checks_gen.rs

@@ -282,6 +282,11 @@ pub enum CheckCodePrefix {
     PGH0,
     PGH00,
     PGH001,
+    PLC,
+    PLC3,
+    PLC30,
+    PLC300,
+    PLC3002,
     PLE,
     PLE1,
     PLE11,
@@ -1161,6 +1166,11 @@ impl CheckCodePrefix {
             CheckCodePrefix::PGH0 => vec![CheckCode::PGH001],
             CheckCodePrefix::PGH00 => vec![CheckCode::PGH001],
             CheckCodePrefix::PGH001 => vec![CheckCode::PGH001],
+            CheckCodePrefix::PLC => vec![CheckCode::PLC3002],
+            CheckCodePrefix::PLC3 => vec![CheckCode::PLC3002],
+            CheckCodePrefix::PLC30 => vec![CheckCode::PLC3002],
+            CheckCodePrefix::PLC300 => vec![CheckCode::PLC3002],
+            CheckCodePrefix::PLC3002 => vec![CheckCode::PLC3002],
             CheckCodePrefix::PLE => vec![CheckCode::PLE1142],
             CheckCodePrefix::PLE1 => vec![CheckCode::PLE1142],
             CheckCodePrefix::PLE11 => vec![CheckCode::PLE1142],
@@ -1637,6 +1647,11 @@ impl CheckCodePrefix {
             CheckCodePrefix::PGH0 => SuffixLength::One,
             CheckCodePrefix::PGH00 => SuffixLength::Two,
             CheckCodePrefix::PGH001 => SuffixLength::Three,
+            CheckCodePrefix::PLC => SuffixLength::Zero,
+            CheckCodePrefix::PLC3 => SuffixLength::One,
+            CheckCodePrefix::PLC30 => SuffixLength::Two,
+            CheckCodePrefix::PLC300 => SuffixLength::Three,
+            CheckCodePrefix::PLC3002 => SuffixLength::Four,
             CheckCodePrefix::PLE => SuffixLength::Zero,
             CheckCodePrefix::PLE1 => SuffixLength::One,
             CheckCodePrefix::PLE11 => SuffixLength::Two,
@@ -1741,6 +1756,7 @@ pub const CATEGORIES: &[CheckCodePrefix] = &[
     CheckCodePrefix::M,
     CheckCodePrefix::N,
     CheckCodePrefix::PGH,
+    CheckCodePrefix::PLC,
     CheckCodePrefix::PLE,
     CheckCodePrefix::PLR,
     CheckCodePrefix::Q,

src/pylint/mod.rs

@@ -11,6 +11,7 @@ mod tests {
     use crate::linter::test_path;
     use crate::Settings;
 
+    #[test_case(CheckCode::PLC3002, Path::new("unnecessary_direct_lambda_call.py"); "PLC3002")]
     #[test_case(CheckCode::PLR0206, Path::new("property_with_parameters.py"); "PLR0206")]
     #[test_case(CheckCode::PLE1142, Path::new("await_outside_async.py"); "PLE1142")]
     fn checks(check_code: CheckCode, path: &Path) -> Result<()> {

src/pylint/plugins.rs

@@ -5,6 +5,16 @@ use crate::check_ast::Checker;
 use crate::checks::CheckKind;
 use crate::Check;
 
+/// PLC3002
+pub fn unnecessary_direct_lambda_call(checker: &mut Checker, expr: &Expr, func: &Expr) {
+    if let ExprKind::Lambda { .. } = &func.node {
+        checker.add_check(Check::new(
+            CheckKind::UnnecessaryDirectLambdaCall,
+            Range::from_located(expr),
+        ));
+    }
+}
+
 /// PLR0206
 pub fn property_with_parameters(
     checker: &mut Checker,

src/pylint/snapshots/ruff__pylint__tests__unnecessary_direct_lambda_call.py.snap

@@ -0,0 +1,29 @@
+---
+source: src/pylint/mod.rs
+expression: checks
+---
+- kind: UnnecessaryDirectLambdaCall
+  location:
+    row: 4
+    column: 4
+  end_location:
+    row: 4
+    column: 33
+  fix: ~
+- kind: UnnecessaryDirectLambdaCall
+  location:
+    row: 5
+    column: 8
+  end_location:
+    row: 5
+    column: 27
+  fix: ~
+- kind: UnnecessaryDirectLambdaCall
+  location:
+    row: 5
+    column: 29
+  end_location:
+    row: 5
+    column: 47
+  fix: ~
+