[flake8-bugbear] Offer unsafe autofix for no-explicit-stacklevel (B028) (#14829)

This PR introduces an unsafe autofix for [no-explicit-stacklevel
(B028)](https://docs.astral.sh/ruff/rules/no-explicit-stacklevel/#no-explicit-stacklevel-b028):
we add the `stacklevel` argument, set to `2`.

Closes #14805

crates/ruff_linter/resources/test/fixtures/flake8_bugbear/B028.py

@@ -9,3 +9,9 @@ warnings.warn(DeprecationWarning("test"))
 warnings.warn(DeprecationWarning("test"), source=None)
 warnings.warn(DeprecationWarning("test"), source=None, stacklevel=2)
 warnings.warn(DeprecationWarning("test"), stacklevel=1)
+
+warnings.warn(
+        DeprecationWarning("test"),
+        # some comments here
+        source = None # no trailing comma
+    )

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

@@ -1,9 +1,9 @@
-use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Fix};
 use ruff_macros::{derive_message_formats, ViolationMetadata};
 use ruff_python_ast::{self as ast};
 use ruff_text_size::Ranged;
 
-use crate::checkers::ast::Checker;
+use crate::{checkers::ast::Checker, fix::edits::add_argument};
 
 /// ## What it does
 /// Checks for `warnings.warn` calls without an explicit `stacklevel` keyword
@@ -28,16 +28,26 @@ use crate::checkers::ast::Checker;
 /// warnings.warn("This is a warning", stacklevel=2)
 /// ```
 ///
+/// ## Fix safety
+/// This rule's fix is marked as unsafe because it changes
+/// the behavior of the code. Moreover, the fix will assign
+/// a stacklevel of 2, while the user may wish to assign a
+/// higher stacklevel to address the diagnostic.
+///
 /// ## References
 /// - [Python documentation: `warnings.warn`](https://docs.python.org/3/library/warnings.html#warnings.warn)
 #[derive(ViolationMetadata)]
 pub(crate) struct NoExplicitStacklevel;
 
-impl Violation for NoExplicitStacklevel {
+impl AlwaysFixableViolation for NoExplicitStacklevel {
     #[derive_message_formats]
     fn message(&self) -> String {
         "No explicit `stacklevel` keyword argument found".to_string()
     }
+
+    fn fix_title(&self) -> String {
+        "Set `stacklevel=2`".to_string()
+    }
 }
 
 /// B028
@@ -53,8 +63,16 @@ pub(crate) fn no_explicit_stacklevel(checker: &mut Checker, call: &ast::ExprCall
     if call.arguments.find_keyword("stacklevel").is_some() {
         return;
     }
+    let mut diagnostic = Diagnostic::new(NoExplicitStacklevel, call.func.range());
 
-    checker
-        .diagnostics
-        .push(Diagnostic::new(NoExplicitStacklevel, call.func.range()));
+    let edit = add_argument(
+        "stacklevel=2",
+        &call.arguments,
+        checker.comment_ranges(),
+        checker.locator().contents(),
+    );
+
+    diagnostic.set_fix(Fix::unsafe_edit(edit));
+
+    checker.diagnostics.push(diagnostic);
 }

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B028_B028.py.snap

@@ -1,8 +1,7 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
-snapshot_kind: text
 ---
-B028.py:8:1: B028 No explicit `stacklevel` keyword argument found
+B028.py:8:1: B028 [*] No explicit `stacklevel` keyword argument found
    |
  6 | """
  7 | 
@@ -11,8 +10,19 @@ B028.py:8:1: B028 No explicit `stacklevel` keyword argument found
  9 | warnings.warn(DeprecationWarning("test"), source=None)
 10 | warnings.warn(DeprecationWarning("test"), source=None, stacklevel=2)
    |
+   = help: Set `stacklevel=2`
 
-B028.py:9:1: B028 No explicit `stacklevel` keyword argument found
+ℹ Unsafe fix
+5 5 | B028 - on lines 8 and 9
+6 6 | """
+7 7 | 
+8   |-warnings.warn(DeprecationWarning("test"))
+  8 |+warnings.warn(DeprecationWarning("test"), stacklevel=2)
+9 9 | warnings.warn(DeprecationWarning("test"), source=None)
+10 10 | warnings.warn(DeprecationWarning("test"), source=None, stacklevel=2)
+11 11 | warnings.warn(DeprecationWarning("test"), stacklevel=1)
+
+B028.py:9:1: B028 [*] No explicit `stacklevel` keyword argument found
    |
  8 | warnings.warn(DeprecationWarning("test"))
  9 | warnings.warn(DeprecationWarning("test"), source=None)
@@ -20,3 +30,34 @@ B028.py:9:1: B028 No explicit `stacklevel` keyword argument found
 10 | warnings.warn(DeprecationWarning("test"), source=None, stacklevel=2)
 11 | warnings.warn(DeprecationWarning("test"), stacklevel=1)
    |
+   = help: Set `stacklevel=2`
+
+ℹ Unsafe fix
+6  6  | """
+7  7  | 
+8  8  | warnings.warn(DeprecationWarning("test"))
+9     |-warnings.warn(DeprecationWarning("test"), source=None)
+10 9  | warnings.warn(DeprecationWarning("test"), source=None, stacklevel=2)
+   10 |+warnings.warn(DeprecationWarning("test"), source=None, stacklevel=2)
+11 11 | warnings.warn(DeprecationWarning("test"), stacklevel=1)
+12 12 | 
+13 13 | warnings.warn(
+
+B028.py:13:1: B028 [*] No explicit `stacklevel` keyword argument found
+   |
+11 | warnings.warn(DeprecationWarning("test"), stacklevel=1)
+12 | 
+13 | warnings.warn(
+   | ^^^^^^^^^^^^^ B028
+14 |         DeprecationWarning("test"),
+15 |         # some comments here
+   |
+   = help: Set `stacklevel=2`
+
+ℹ Unsafe fix
+13 13 | warnings.warn(
+14 14 |         DeprecationWarning("test"),
+15 15 |         # some comments here
+16    |-        source = None # no trailing comma
+   16 |+        source = None, stacklevel=2 # no trailing comma
+17 17 |     )