[flake8-bugbear] Mark B905 and B912 fixes as unsafe (#20695)

Resolves #20694

This PR updates the `zip_without_explicit_strict` and
`map_without_explicit_strict` rules so their fixes are always marked
unsafe, following Brent's guidance that adding `strict=False` can
silently preserve buggy behaviour when inputs differ. The fix safety
docs now spell out that reasoning, the applicability drops to `Unsafe`,
and the snapshots were refreshed so Ruff clearly warns users before
applying the edit.

Author: terror

crates/ruff_linter/src/rules/flake8_bugbear/rules/map_without_explicit_strict.rs

@@ -34,9 +34,10 @@ use crate::{AlwaysFixableViolation, Applicability, Fix};
 /// ```
 ///
 /// ## Fix safety
-/// This rule's fix is marked as unsafe for `map` calls that contain
-/// `**kwargs`, as adding a `strict` keyword argument to such a call may lead
-/// to a duplicate keyword argument error.
+/// This rule's fix is marked as unsafe. While adding `strict=False` preserves
+/// the runtime behavior, it can obscure situations where the iterables are of
+/// unequal length. Ruff prefers to alert users so they can choose the intended
+/// behavior themselves.
 ///
 /// ## References
 /// - [Python documentation: `map`](https://docs.python.org/3/library/functions.html#map)
@@ -73,17 +74,7 @@ pub(crate) fn map_without_explicit_strict(checker: &Checker, call: &ast::ExprCal
                     checker.comment_ranges(),
                     checker.locator().contents(),
                 ),
-                // If the function call contains `**kwargs`, mark the fix as unsafe.
-                if call
-                    .arguments
-                    .keywords
-                    .iter()
-                    .any(|keyword| keyword.arg.is_none())
-                {
-                    Applicability::Unsafe
-                } else {
-                    Applicability::Safe
-                },
+                Applicability::Unsafe,
             ));
     }
 }

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

@@ -31,9 +31,10 @@ use crate::{AlwaysFixableViolation, Applicability, Fix};
 /// ```
 ///
 /// ## Fix safety
-/// This rule's fix is marked as unsafe for `zip` calls that contain
-/// `**kwargs`, as adding a `strict` keyword argument to such a call may lead
-/// to a duplicate keyword argument error.
+/// This rule's fix is marked as unsafe. While adding `strict=False` preserves
+/// the runtime behavior, it can obscure situations where the iterables are of
+/// unequal length. Ruff prefers to alert users so they can choose the intended
+/// behavior themselves.
 ///
 /// ## References
 /// - [Python documentation: `zip`](https://docs.python.org/3/library/functions.html#zip)
@@ -68,17 +69,7 @@ pub(crate) fn zip_without_explicit_strict(checker: &Checker, call: &ast::ExprCal
                     checker.comment_ranges(),
                     checker.locator().contents(),
                 ),
-                // If the function call contains `**kwargs`, mark the fix as unsafe.
-                if call
-                    .arguments
-                    .keywords
-                    .iter()
-                    .any(|keyword| keyword.arg.is_none())
-                {
-                    Applicability::Unsafe
-                } else {
-                    Applicability::Safe
-                },
+                Applicability::Unsafe,
             ));
     }
 }

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B905.py.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
+assertion_line: 156
 ---
 B905 [*] `zip()` without an explicit `strict=` parameter
  --> B905.py:4:1
@@ -19,6 +20,7 @@ help: Add explicit value for parameter `strict=`
 5 | zip(range(3))
 6 | zip("a", "b")
 7 | zip("a", "b", *zip("c"))
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
  --> B905.py:5:1
@@ -39,6 +41,7 @@ help: Add explicit value for parameter `strict=`
 6 | zip("a", "b")
 7 | zip("a", "b", *zip("c"))
 8 | zip(zip("a"), strict=False)
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
  --> B905.py:6:1
@@ -59,6 +62,7 @@ help: Add explicit value for parameter `strict=`
 7 | zip("a", "b", *zip("c"))
 8 | zip(zip("a"), strict=False)
 9 | zip(zip("a", strict=True))
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
  --> B905.py:7:1
@@ -79,6 +83,7 @@ help: Add explicit value for parameter `strict=`
 8  | zip(zip("a"), strict=False)
 9  | zip(zip("a", strict=True))
 10 | 
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
  --> B905.py:7:16
@@ -99,6 +104,7 @@ help: Add explicit value for parameter `strict=`
 8  | zip(zip("a"), strict=False)
 9  | zip(zip("a", strict=True))
 10 | 
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
  --> B905.py:8:5
@@ -118,6 +124,7 @@ help: Add explicit value for parameter `strict=`
 9  | zip(zip("a", strict=True))
 10 | 
 11 | # OK
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
   --> B905.py:9:1
@@ -138,6 +145,7 @@ help: Add explicit value for parameter `strict=`
 10 | 
 11 | # OK
 12 | zip(range(3), strict=True)
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
   --> B905.py:24:1
@@ -156,6 +164,7 @@ help: Add explicit value for parameter `strict=`
 25 | zip([1, 2, 3], repeat(1, times=4))
 26 | 
 27 | import builtins
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
   --> B905.py:25:1
@@ -176,6 +185,7 @@ help: Add explicit value for parameter `strict=`
 26 | 
 27 | import builtins
 28 | # Still an error even though it uses the qualified name
+note: This is an unsafe fix and may change runtime behavior
 
 B905 [*] `zip()` without an explicit `strict=` parameter
   --> B905.py:29:1
@@ -191,3 +201,4 @@ help: Add explicit value for parameter `strict=`
 28 | # Still an error even though it uses the qualified name
    - builtins.zip([1, 2, 3])
 29 + builtins.zip([1, 2, 3], strict=False)
+note: This is an unsafe fix and may change runtime behavior

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__preview__B912_B912.py.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
+assertion_line: 112
 ---
 B912 [*] `map()` without an explicit `strict=` parameter
  --> B912.py:5:1
@@ -20,6 +21,7 @@ help: Add explicit value for parameter `strict=`
 6 | map(lambda x, y, z: x + y + z, [1, 2, 3], [4, 5, 6], [7, 8, 9])
 7 | map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6], *map(lambda x: x, [7, 8, 9]))
 8 | map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6], *map(lambda x: x, [7, 8, 9]), strict=False)
+note: This is an unsafe fix and may change runtime behavior
 
 B912 [*] `map()` without an explicit `strict=` parameter
  --> B912.py:6:1
@@ -40,6 +42,7 @@ help: Add explicit value for parameter `strict=`
 7 | map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6], *map(lambda x: x, [7, 8, 9]))
 8 | map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6], *map(lambda x: x, [7, 8, 9]), strict=False)
 9 | map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6], *map(lambda x: x, [7, 8, 9], strict=True))
+note: This is an unsafe fix and may change runtime behavior
 
 B912 [*] `map()` without an explicit `strict=` parameter
  --> B912.py:7:1
@@ -61,6 +64,7 @@ help: Add explicit value for parameter `strict=`
 9  | map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6], *map(lambda x: x, [7, 8, 9], strict=True))
 10 | 
 11 | # Errors (limited iterators).
+note: This is an unsafe fix and may change runtime behavior
 
 B912 [*] `map()` without an explicit `strict=` parameter
   --> B912.py:9:1
@@ -81,6 +85,7 @@ help: Add explicit value for parameter `strict=`
 10 | 
 11 | # Errors (limited iterators).
 12 | map(lambda x, y: x + y, [1, 2, 3], repeat(1, 1))
+note: This is an unsafe fix and may change runtime behavior
 
 B912 [*] `map()` without an explicit `strict=` parameter
   --> B912.py:12:1
@@ -99,6 +104,7 @@ help: Add explicit value for parameter `strict=`
 13 | map(lambda x, y: x + y, [1, 2, 3], repeat(1, times=4))
 14 | 
 15 | import builtins
+note: This is an unsafe fix and may change runtime behavior
 
 B912 [*] `map()` without an explicit `strict=` parameter
   --> B912.py:13:1
@@ -119,6 +125,7 @@ help: Add explicit value for parameter `strict=`
 14 | 
 15 | import builtins
 16 | # Still an error even though it uses the qualified name
+note: This is an unsafe fix and may change runtime behavior
 
 B912 [*] `map()` without an explicit `strict=` parameter
   --> B912.py:17:1
@@ -139,3 +146,4 @@ help: Add explicit value for parameter `strict=`
 18 | 
 19 | # OK
 20 | map(lambda x: x, [1, 2, 3], strict=True)
+note: This is an unsafe fix and may change runtime behavior