[perflint] Add PERF101 with autofix

crates/ruff/resources/test/fixtures/perflint/PERF101.py

@@ -0,0 +1,52 @@
+foo_tuple = (1, 2, 3)
+foo_list = [1, 2, 3]
+foo_set = {1, 2, 3}
+foo_dict = {1: 2, 3: 4}
+foo_int = 123
+
+for i in list(foo_tuple):  # PERF101
+    pass
+
+for i in list(foo_list):  # PERF101
+    pass
+
+for i in list(foo_set):  # PERF101
+    pass
+
+for i in list((1, 2, 3)):  # PERF101
+    pass
+
+for i in list([1, 2, 3]):  # PERF101
+    pass
+
+for i in list({1, 2, 3}):  # PERF101
+    pass
+
+for i in list(
+    {
+    1,
+    2,
+    3,
+    }
+):
+    pass
+
+for i in list( # Comment
+    {1, 2, 3}
+):  # PERF101
+    pass
+
+for i in list(foo_dict):  # Ok
+    pass
+
+for i in list(1):  # Ok
+    pass
+
+for i in list(foo_int):  # Ok
+    pass
+
+
+import itertools
+
+for i in itertools.product(foo_int):  # Ok
+    pass

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

@@ -1481,6 +1481,9 @@ where
                 if self.enabled(Rule::IncorrectDictIterator) {
                     perflint::rules::incorrect_dict_iterator(self, target, iter);
                 }
+                if self.enabled(Rule::UnnecessaryListCast) {
+                    perflint::rules::unnecessary_list_cast(self, iter);
+                }
             }
             Stmt::Try(ast::StmtTry {
                 body,

crates/ruff/src/codes.rs

@@ -784,6 +784,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Airflow, "001") => (RuleGroup::Unspecified, rules::airflow::rules::AirflowVariableNameTaskIdMismatch),
 
         // perflint
+        (Perflint, "101") => (RuleGroup::Unspecified, rules::perflint::rules::UnnecessaryListCast),
         (Perflint, "102") => (RuleGroup::Unspecified, rules::perflint::rules::IncorrectDictIterator),
 
         // flake8-fixme

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

@@ -13,6 +13,7 @@ mod tests {
     use crate::settings::Settings;
     use crate::test::test_path;
 
+    #[test_case(Rule::UnnecessaryListCast, Path::new("PERF101.py"))]
     #[test_case(Rule::IncorrectDictIterator, Path::new("PERF102.py"))]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());

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

@@ -1,3 +1,5 @@
-pub(crate) use incorrect_dict_iterator::{incorrect_dict_iterator, IncorrectDictIterator};
+pub(crate) use incorrect_dict_iterator::*;
+pub(crate) use unnecessary_list_cast::*;
 
 mod incorrect_dict_iterator;
+mod unnecessary_list_cast;

crates/ruff/src/rules/perflint/rules/unnecessary_list_cast.rs

@@ -0,0 +1,129 @@
+use ruff_text_size::TextRange;
+use rustpython_parser::ast::{self, Expr};
+
+use ruff_diagnostics::{AlwaysAutofixableViolation, Diagnostic, Edit, Fix};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::prelude::Stmt;
+
+use crate::checkers::ast::Checker;
+use crate::registry::AsRule;
+
+/// ## What it does
+/// Checks for explicit casts to `list` on for-loop iterables.
+///
+/// ## Why is this bad?
+/// Using a `list()` call to eagerly iterate over an already-iterable type
+/// (like a tuple, list, or set) is inefficient, as it forces Python to create
+/// a new list unnecessarily.
+///
+/// Removing the `list()` call will not change the behavior of the code, but
+/// may improve performance.
+///
+/// ## Example
+/// ```python
+/// items = (1, 2, 3)
+/// for i in list(items):
+///     print(i)
+/// ```
+///
+/// Use instead:
+/// ```python
+/// items = (1, 2, 3)
+/// for i in items:
+///     print(i)
+/// ```
+#[violation]
+pub struct UnnecessaryListCast;
+
+impl AlwaysAutofixableViolation for UnnecessaryListCast {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Do not cast an iterable to `list` before iterating over it")
+    }
+
+    fn autofix_title(&self) -> String {
+        format!("Remove `list()` cast")
+    }
+}
+
+/// PERF101
+pub(crate) fn unnecessary_list_cast(checker: &mut Checker, iter: &Expr) {
+    let Expr::Call(ast::ExprCall{ func, args, range: list_range, ..}) = iter else {
+        return;
+    };
+
+    if args.len() != 1 {
+        return;
+    }
+
+    let Expr::Name(ast::ExprName { id, .. }) = func.as_ref() else{
+        return;
+    };
+
+    if !(id == "list" && checker.semantic().is_builtin("list")) {
+        return;
+    }
+
+    match &args[0] {
+        Expr::Tuple(ast::ExprTuple {
+            range: iterable_range,
+            ..
+        })
+        | Expr::List(ast::ExprList {
+            range: iterable_range,
+            ..
+        })
+        | Expr::Set(ast::ExprSet {
+            range: iterable_range,
+            ..
+        }) => {
+            let mut diagnostic = Diagnostic::new(UnnecessaryListCast, *list_range);
+            if checker.patch(diagnostic.kind.rule()) {
+                diagnostic.set_fix(remove_cast(*list_range, *iterable_range));
+            }
+            checker.diagnostics.push(diagnostic);
+        }
+        Expr::Name(ast::ExprName {
+            id,
+            range: iterable_range,
+            ..
+        }) => {
+            let scope = checker.semantic().scope();
+            if let Some(binding_id) = scope.get(id) {
+                let binding = checker.semantic().binding(binding_id);
+                if binding.kind.is_assignment() || binding.kind.is_named_expr_assignment() {
+                    if let Some(parent_id) = binding.source {
+                        let parent = checker.semantic().stmts[parent_id];
+                        if let Stmt::Assign(ast::StmtAssign { value, .. })
+                        | Stmt::AnnAssign(ast::StmtAnnAssign {
+                            value: Some(value), ..
+                        })
+                        | Stmt::AugAssign(ast::StmtAugAssign { value, .. }) = parent
+                        {
+                            if matches!(
+                                value.as_ref(),
+                                Expr::Tuple(_) | Expr::List(_) | Expr::Set(_)
+                            ) {
+                                let mut diagnostic =
+                                    Diagnostic::new(UnnecessaryListCast, *list_range);
+                                if checker.patch(diagnostic.kind.rule()) {
+                                    diagnostic.set_fix(remove_cast(*list_range, *iterable_range));
+                                }
+                                checker.diagnostics.push(diagnostic);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        _ => {}
+    }
+}
+
+/// Generate a [`Fix`] to remove a `list` cast from an expression.
+fn remove_cast(list_range: TextRange, iterable_range: TextRange) -> Fix {
+    Fix::automatic_edits(
+        Edit::deletion(list_range.start(), iterable_range.start()),
+        [Edit::deletion(iterable_range.end(), list_range.end())],
+    )
+}

crates/ruff/src/rules/perflint/snapshots/ruff__rules__perflint__tests__PERF101_PERF101.py.snap

@@ -0,0 +1,183 @@
+---
+source: crates/ruff/src/rules/perflint/mod.rs
+---
+PERF101.py:7:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+  |
+5 | foo_int = 123
+6 | 
+7 | for i in list(foo_tuple):  # PERF101
+  |          ^^^^^^^^^^^^^^^ PERF101
+8 |     pass
+  |
+  = help: Remove `list()` cast
+
+ℹ Fix
+4 4 | foo_dict = {1: 2, 3: 4}
+5 5 | foo_int = 123
+6 6 | 
+7   |-for i in list(foo_tuple):  # PERF101
+  7 |+for i in foo_tuple:  # PERF101
+8 8 |     pass
+9 9 | 
+10 10 | for i in list(foo_list):  # PERF101
+
+PERF101.py:10:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+   |
+ 8 |     pass
+ 9 | 
+10 | for i in list(foo_list):  # PERF101
+   |          ^^^^^^^^^^^^^^ PERF101
+11 |     pass
+   |
+   = help: Remove `list()` cast
+
+ℹ Fix
+7  7  | for i in list(foo_tuple):  # PERF101
+8  8  |     pass
+9  9  | 
+10    |-for i in list(foo_list):  # PERF101
+   10 |+for i in foo_list:  # PERF101
+11 11 |     pass
+12 12 | 
+13 13 | for i in list(foo_set):  # PERF101
+
+PERF101.py:13:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+   |
+11 |     pass
+12 | 
+13 | for i in list(foo_set):  # PERF101
+   |          ^^^^^^^^^^^^^ PERF101
+14 |     pass
+   |
+   = help: Remove `list()` cast
+
+ℹ Fix
+10 10 | for i in list(foo_list):  # PERF101
+11 11 |     pass
+12 12 | 
+13    |-for i in list(foo_set):  # PERF101
+   13 |+for i in foo_set:  # PERF101
+14 14 |     pass
+15 15 | 
+16 16 | for i in list((1, 2, 3)):  # PERF101
+
+PERF101.py:16:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+   |
+14 |     pass
+15 | 
+16 | for i in list((1, 2, 3)):  # PERF101
+   |          ^^^^^^^^^^^^^^^ PERF101
+17 |     pass
+   |
+   = help: Remove `list()` cast
+
+ℹ Fix
+13 13 | for i in list(foo_set):  # PERF101
+14 14 |     pass
+15 15 | 
+16    |-for i in list((1, 2, 3)):  # PERF101
+   16 |+for i in (1, 2, 3):  # PERF101
+17 17 |     pass
+18 18 | 
+19 19 | for i in list([1, 2, 3]):  # PERF101
+
+PERF101.py:19:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+   |
+17 |     pass
+18 | 
+19 | for i in list([1, 2, 3]):  # PERF101
+   |          ^^^^^^^^^^^^^^^ PERF101
+20 |     pass
+   |
+   = help: Remove `list()` cast
+
+ℹ Fix
+16 16 | for i in list((1, 2, 3)):  # PERF101
+17 17 |     pass
+18 18 | 
+19    |-for i in list([1, 2, 3]):  # PERF101
+   19 |+for i in [1, 2, 3]:  # PERF101
+20 20 |     pass
+21 21 | 
+22 22 | for i in list({1, 2, 3}):  # PERF101
+
+PERF101.py:22:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+   |
+20 |     pass
+21 | 
+22 | for i in list({1, 2, 3}):  # PERF101
+   |          ^^^^^^^^^^^^^^^ PERF101
+23 |     pass
+   |
+   = help: Remove `list()` cast
+
+ℹ Fix
+19 19 | for i in list([1, 2, 3]):  # PERF101
+20 20 |     pass
+21 21 | 
+22    |-for i in list({1, 2, 3}):  # PERF101
+   22 |+for i in {1, 2, 3}:  # PERF101
+23 23 |     pass
+24 24 | 
+25 25 | for i in list(
+
+PERF101.py:25:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+   |
+23 |       pass
+24 |   
+25 |   for i in list(
+   |  __________^
+26 | |     {
+27 | |     1,
+28 | |     2,
+29 | |     3,
+30 | |     }
+31 | | ):
+   | |_^ PERF101
+32 |       pass
+   |
+   = help: Remove `list()` cast
+
+ℹ Fix
+22 22 | for i in list({1, 2, 3}):  # PERF101
+23 23 |     pass
+24 24 | 
+25    |-for i in list(
+26    |-    {
+   25 |+for i in {
+27 26 |     1,
+28 27 |     2,
+29 28 |     3,
+30    |-    }
+31    |-):
+   29 |+    }:
+32 30 |     pass
+33 31 | 
+34 32 | for i in list( # Comment
+
+PERF101.py:34:10: PERF101 [*] Do not cast an iterable to `list` before iterating over it
+   |
+32 |       pass
+33 |   
+34 |   for i in list( # Comment
+   |  __________^
+35 | |     {1, 2, 3}
+36 | | ):  # PERF101
+   | |_^ PERF101
+37 |       pass
+   |
+   = help: Remove `list()` cast
+
+ℹ Fix
+31 31 | ):
+32 32 |     pass
+33 33 | 
+34    |-for i in list( # Comment
+35    |-    {1, 2, 3}
+36    |-):  # PERF101
+   34 |+for i in {1, 2, 3}:  # PERF101
+37 35 |     pass
+38 36 | 
+39 37 | for i in list(foo_dict):  # Ok
+
+