ignore if using infinite iterators in B905 (#4914)

crates/ruff/resources/test/fixtures/flake8_bugbear/B905.py

@@ -1,3 +1,6 @@
+from itertools import count, cycle, repeat
+
+# Errors
 zip()
 zip(range(3))
 zip("a", "b")
@@ -5,6 +8,18 @@ zip("a", "b", *zip("c"))
 zip(zip("a"), strict=False)
 zip(zip("a", strict=True))
 
+# OK
 zip(range(3), strict=True)
 zip("a", "b", strict=False)
 zip("a", "b", "c", strict=True)
+
+# OK (infinite iterators).
+zip([1, 2, 3], cycle("ABCDEF"))
+zip([1, 2, 3], count())
+zip([1, 2, 3], repeat(1))
+zip([1, 2, 3], repeat(1, None))
+zip([1, 2, 3], repeat(1, times=None))
+
+# Errors (limited iterators).
+zip([1, 2, 3], repeat(1, 1))
+zip([1, 2, 3], repeat(1, times=4))

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

@@ -2633,7 +2633,9 @@ where
                 if self.enabled(Rule::ZipWithoutExplicitStrict)
                     && self.settings.target_version >= PythonVersion::Py310
                 {
-                    flake8_bugbear::rules::zip_without_explicit_strict(self, expr, func, keywords);
+                    flake8_bugbear::rules::zip_without_explicit_strict(
+                        self, expr, func, args, keywords,
+                    );
                 }
                 if self.enabled(Rule::NoExplicitStacklevel) {
                     flake8_bugbear::rules::no_explicit_stacklevel(self, func, args, keywords);

crates/ruff/src/rules/flake8_bugbear/rules/zip_without_explicit_strict.rs

@@ -2,6 +2,8 @@ use rustpython_parser::ast::{self, Expr, Keyword, Ranged};
 
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::helpers::is_const_none;
+use ruff_python_semantic::model::SemanticModel;
 
 use crate::checkers::ast::Checker;
 
@@ -20,6 +22,7 @@ pub(crate) fn zip_without_explicit_strict(
     checker: &mut Checker,
     expr: &Expr,
     func: &Expr,
+    args: &[Expr],
     kwargs: &[Keyword],
 ) {
     if let Expr::Name(ast::ExprName { id, .. }) = func {
@@ -28,6 +31,9 @@ pub(crate) fn zip_without_explicit_strict(
             && !kwargs
                 .iter()
                 .any(|keyword| keyword.arg.as_ref().map_or(false, |name| name == "strict"))
+            && !args
+                .iter()
+                .any(|arg| is_infinite_iterator(arg, checker.semantic_model()))
         {
             checker
                 .diagnostics
@@ -35,3 +41,40 @@ pub(crate) fn zip_without_explicit_strict(
         }
     }
 }
+
+/// Return `true` if the [`Expr`] appears to be an infinite iterator (e.g., a call to
+/// `itertools.cycle` or similar).
+fn is_infinite_iterator(arg: &Expr, model: &SemanticModel) -> bool {
+    let Expr::Call(ast::ExprCall { func, args, keywords, .. }) = &arg else {
+        return false;
+    };
+
+    return model
+        .resolve_call_path(func)
+        .map_or(false, |call_path| match call_path.as_slice() {
+            ["itertools", "cycle" | "count"] => true,
+            ["itertools", "repeat"] => {
+                // Ex) `itertools.repeat(1)`
+                if keywords.is_empty() && args.len() == 1 {
+                    return true;
+                }
+
+                // Ex) `itertools.repeat(1, None)`
+                if args.len() == 2 && is_const_none(&args[1]) {
+                    return true;
+                }
+
+                // Ex) `iterools.repeat(1, times=None)`
+                for keyword in keywords {
+                    if keyword.arg.as_ref().map_or(false, |name| name == "times") {
+                        if is_const_none(&keyword.value) {
+                            return true;
+                        }
+                    }
+                }
+
+                false
+            }
+            _ => false,
+        });
+}

crates/ruff/src/rules/flake8_bugbear/snapshots/ruff__rules__flake8_bugbear__tests__B905_B905.py.snap

@@ -1,70 +1,88 @@
 ---
 source: crates/ruff/src/rules/flake8_bugbear/mod.rs
 ---
-B905.py:1:1: B905 `zip()` without an explicit `strict=` parameter
-  |
-1 | zip()
-  | ^^^^^ B905
-2 | zip(range(3))
-3 | zip("a", "b")
-  |
-
-B905.py:2:1: B905 `zip()` without an explicit `strict=` parameter
-  |
-2 | zip()
-3 | zip(range(3))
-  | ^^^^^^^^^^^^^ B905
-4 | zip("a", "b")
-5 | zip("a", "b", *zip("c"))
-  |
-
-B905.py:3:1: B905 `zip()` without an explicit `strict=` parameter
-  |
-3 | zip()
-4 | zip(range(3))
-5 | zip("a", "b")
-  | ^^^^^^^^^^^^^ B905
-6 | zip("a", "b", *zip("c"))
-7 | zip(zip("a"), strict=False)
-  |
-
 B905.py:4:1: B905 `zip()` without an explicit `strict=` parameter
   |
-4 | zip(range(3))
-5 | zip("a", "b")
-6 | zip("a", "b", *zip("c"))
-  | ^^^^^^^^^^^^^^^^^^^^^^^^ B905
-7 | zip(zip("a"), strict=False)
-8 | zip(zip("a", strict=True))
+4 | # Errors
+5 | zip()
+  | ^^^^^ B905
+6 | zip(range(3))
+7 | zip("a", "b")
   |
 
-B905.py:4:16: B905 `zip()` without an explicit `strict=` parameter
+B905.py:5:1: B905 `zip()` without an explicit `strict=` parameter
   |
-4 | zip(range(3))
-5 | zip("a", "b")
-6 | zip("a", "b", *zip("c"))
-  |                ^^^^^^^^ B905
-7 | zip(zip("a"), strict=False)
-8 | zip(zip("a", strict=True))
-  |
-
-B905.py:5:5: B905 `zip()` without an explicit `strict=` parameter
-  |
-5 | zip("a", "b")
-6 | zip("a", "b", *zip("c"))
-7 | zip(zip("a"), strict=False)
-  |     ^^^^^^^^ B905
-8 | zip(zip("a", strict=True))
+5 | # Errors
+6 | zip()
+7 | zip(range(3))
+  | ^^^^^^^^^^^^^ B905
+8 | zip("a", "b")
+9 | zip("a", "b", *zip("c"))
   |
 
 B905.py:6:1: B905 `zip()` without an explicit `strict=` parameter
    |
- 6 | zip("a", "b", *zip("c"))
- 7 | zip(zip("a"), strict=False)
- 8 | zip(zip("a", strict=True))
+ 6 | zip()
+ 7 | zip(range(3))
+ 8 | zip("a", "b")
+   | ^^^^^^^^^^^^^ B905
+ 9 | zip("a", "b", *zip("c"))
+10 | zip(zip("a"), strict=False)
+   |
+
+B905.py:7:1: B905 `zip()` without an explicit `strict=` parameter
+   |
+ 7 | zip(range(3))
+ 8 | zip("a", "b")
+ 9 | zip("a", "b", *zip("c"))
+   | ^^^^^^^^^^^^^^^^^^^^^^^^ B905
+10 | zip(zip("a"), strict=False)
+11 | zip(zip("a", strict=True))
+   |
+
+B905.py:7:16: B905 `zip()` without an explicit `strict=` parameter
+   |
+ 7 | zip(range(3))
+ 8 | zip("a", "b")
+ 9 | zip("a", "b", *zip("c"))
+   |                ^^^^^^^^ B905
+10 | zip(zip("a"), strict=False)
+11 | zip(zip("a", strict=True))
+   |
+
+B905.py:8:5: B905 `zip()` without an explicit `strict=` parameter
+   |
+ 8 | zip("a", "b")
+ 9 | zip("a", "b", *zip("c"))
+10 | zip(zip("a"), strict=False)
+   |     ^^^^^^^^ B905
+11 | zip(zip("a", strict=True))
+   |
+
+B905.py:9:1: B905 `zip()` without an explicit `strict=` parameter
+   |
+ 9 | zip("a", "b", *zip("c"))
+10 | zip(zip("a"), strict=False)
+11 | zip(zip("a", strict=True))
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^ B905
- 9 | 
-10 | zip(range(3), strict=True)
+12 | 
+13 | # OK
+   |
+
+B905.py:24:1: B905 `zip()` without an explicit `strict=` parameter
+   |
+24 | # Errors (limited iterators).
+25 | zip([1, 2, 3], repeat(1, 1))
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ B905
+26 | zip([1, 2, 3], repeat(1, times=4))
+   |
+
+B905.py:25:1: B905 `zip()` without an explicit `strict=` parameter
+   |
+25 | # Errors (limited iterators).
+26 | zip([1, 2, 3], repeat(1, 1))
+27 | zip([1, 2, 3], repeat(1, times=4))
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ B905
    |