Fix for psf#4264

CHANGES.md

@@ -15,6 +15,8 @@
   of Black would incorrectly format the contents of certain unusual f-strings containing
   nested strings with the same quote type. Now, Black will crash on such strings until
   support for the new f-string syntax is implemented. (#4270)
+- Fixed a bug where line-ranges exceeding the last code line would not work as expected
+  (#4273)
 
 ### Preview style
 

src/black/__init__.py

@@ -1220,6 +1220,7 @@ def f(
         hey
 
     """
+    lines = adjusted_lines(lines, src_contents, src_contents)
     dst_contents = _format_str_once(src_contents, mode=mode, lines=lines)
     # Forced second pass to work around optional trailing commas (becoming
     # forced trailing commas on pass 2) interacting differently with optional

src/black/ranges.py

@@ -84,11 +84,14 @@ def adjusted_lines(
     """
     lines_mappings = _calculate_lines_mappings(original_source, modified_source)
 
+    original_line_count = len(original_source.splitlines())
     new_lines = []
     # Keep an index of the current search. Since the lines and lines_mappings are
     # sorted, this makes the search complexity linear.
     current_mapping_index = 0
     for start, end in sorted(lines):
+        if end > original_line_count:
+            end = original_line_count
         start_mapping_index = _find_lines_mapping_index(
             start,
             lines_mappings,

tests/test_ranges.py

@@ -27,9 +27,10 @@ def func():
         [(1, 0)],
         [(-8, 0)],
         [(-8, 8)],
-        [(1, 100)],
         [(2, 1)],
         [(0, 8), (3, 1)],
+        [(12, 13)],
+        [(100, 200)],
     ],
 )
 def test_invalid_lines(lines: List[Tuple[int, int]]) -> None:
@@ -76,6 +77,10 @@ def func(arg1, arg2, arg3):
             [(1, 6)],
             [(1, 2)],
         ),
+        (
+            [(1, 100)],
+            [(1, 2)],
+        ),
         (
             [(6, 6)],
             [],
@@ -111,6 +116,10 @@ def test_removals(
             [(1, 2)],
             [(2, 5)],
         ),
+        (
+            [(1, 100)],
+            [(2, 5)],
+        ),
         (
             [(2, 2)],
             [(5, 5)],
@@ -146,6 +155,10 @@ def test_additions(
             [(1, 12)],
             [(1, 11)],
         ),
+        (
+            [(1, 100)],
+            [(1, 11)],
+        ),
         (
             [(10, 10)],
             [(9, 9)],