Handle when pos is equal to line length

crates/ruff_linter/resources/test/fixtures/flake8_bugbear/B006_6.py

@@ -0,0 +1,5 @@
+# Docstring followed by whitespace with no newline
+# Regression test for https://github.com/astral-sh/ruff/issues/7155
+
+def foobar(foor, bar={}):    
+    import os                    

crates/ruff_linter/resources/test/fixtures/flake8_bugbear/B006_7.py

@@ -0,0 +1,5 @@
+# Docstring with no newline
+
+
+def foobar(foor, bar={}):    
+    import os

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

@@ -38,6 +38,8 @@ mod tests {
     #[test_case(Rule::MutableArgumentDefault, Path::new("B006_3.py"))]
     #[test_case(Rule::MutableArgumentDefault, Path::new("B006_4.py"))]
     #[test_case(Rule::MutableArgumentDefault, Path::new("B006_5.py"))]
+    #[test_case(Rule::MutableArgumentDefault, Path::new("B006_6.py"))]
+    #[test_case(Rule::MutableArgumentDefault, Path::new("B006_7.py"))]
     #[test_case(Rule::NoExplicitStacklevel, Path::new("B028.py"))]
     #[test_case(Rule::RaiseLiteral, Path::new("B016.py"))]
     #[test_case(Rule::RaiseWithoutFromInsideExcept, Path::new("B904.py"))]

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

@@ -192,6 +192,12 @@ fn move_initialization(
         } else if statement.is_import_stmt() || statement.is_import_from_stmt() {
             // If the statement in the function is an import, insert _after_ it.
             pos = locator.full_line_end(statement.end());
+            if pos == locator.text_len() {
+                // If the statement is at the end of the file, without a trailing newline, insert
+                // _after_ it with an extra newline.
+                content = format!("{}{}", stylist.line_ending().as_str(), content);
+                break;
+            }
         } else {
             break;
         };

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B006_B006_5.py.snap

@@ -151,7 +151,8 @@ B006_5.py:35:59: B006 [*] Do not use mutable data structures for argument defaul
    35 |+def import_docstring_module_wrong(value: dict[str, str] = None):
 36 36 |     """Docstring"""
 37 37 |     import os
-   38 |+    if value is None:
-   39 |+        value = {}
+   38 |+
+   39 |+    if value is None:
+   40 |+        value = {}
 
 

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B006_B006_6.py.snap

@@ -0,0 +1,25 @@
+---
+source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
+---
+B006_6.py:4:22: B006 [*] Do not use mutable data structures for argument defaults
+  |
+2 | # Regression test for https://github.com/astral-sh/ruff/issues/7155
+3 | 
+4 | def foobar(foor, bar={}):    
+  |                      ^^ B006
+5 |     import os                    
+  |
+  = help: Replace with `None`; initialize within function
+
+ℹ Possible fix
+1 1 | # Docstring followed by whitespace with no newline
+2 2 | # Regression test for https://github.com/astral-sh/ruff/issues/7155
+3 3 | 
+4   |-def foobar(foor, bar={}):    
+5   |-    import os                    
+  4 |+def foobar(foor, bar=None):    
+  5 |+    import os                    
+  6 |+    if bar is None:
+  7 |+        bar = {}
+
+

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B006_B006_7.py.snap

@@ -0,0 +1,23 @@
+---
+source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
+---
+B006_7.py:4:22: B006 [*] Do not use mutable data structures for argument defaults
+  |
+4 | def foobar(foor, bar={}):    
+  |                      ^^ B006
+5 |     import os
+  |
+  = help: Replace with `None`; initialize within function
+
+ℹ Possible fix
+1 1 | # Docstring with no newline
+2 2 | 
+3 3 | 
+4   |-def foobar(foor, bar={}):    
+5   |-    import os
+  4 |+def foobar(foor, bar=None):    
+  5 |+    import os
+  6 |+    if bar is None:
+  7 |+        bar = {}
+
+