chore: improve rich maintenance path

rich/cells.py

@@ -2,11 +2,11 @@
 
 from functools import lru_cache
 from operator import itemgetter
-from typing import Callable, NamedTuple, Sequence, Tuple
+from typing import Callable, NamedTuple, Sequence
 
 from rich._unicode_data import load as load_cell_table
 
-CellSpan = Tuple[int, int, int]
+CellSpan = tuple[int, int, int]
 
 _span_get_cell_len = itemgetter(2)
 
@@ -160,7 +160,7 @@ def _cell_len(text: str, unicode_version: str) -> int:
 
 def split_graphemes(
     text: str, unicode_version: str = "auto"
-) -> "tuple[list[CellSpan], int]":
+) -> tuple[list[CellSpan], int]:
     """Divide text into spans that define a single grapheme, and additionally return the cell length of the whole string.
 
     The returned spans will cover every index in the string, with no gaps. It is possible for some graphemes to have a cell length of zero.

tests/test_cells.py

@@ -11,6 +11,7 @@
     cell_len,
     chop_cells,
     get_character_cell_size,
+    set_cell_size,
     split_graphemes,
     split_text,
 )
@@ -252,3 +253,31 @@ def test_non_printable():
     for ordinal in range(31):
         character = chr(ordinal)
         assert cell_len(character) == 0
+
+
+def test_cell_len_edge_cases() -> None:
+    """cell_len for empty strings, ZWJ sequences, and mixed CJK."""
+    assert cell_len("") == 0
+    assert cell_len("👩\u200d🔧") == 2
+    assert cell_len("👩\u200d👩\u200d👧\u200d👧") == 2
+    assert cell_len("あ1り2") == 6
+
+
+def test_set_cell_size_edge_cases() -> None:
+    """set_cell_size for empty strings and exact-boundary cases."""
+    assert set_cell_size("", 0) == ""
+    assert set_cell_size("", 3) == "   "
+    assert set_cell_size("foo", 3) == "foo"
+    assert set_cell_size("あい", 4) == "あい"
+    assert set_cell_size("あ1り2", 6) == "あ1り2"
+    assert set_cell_size("👩\u200d🔧", 2) == "👩\u200d🔧"
+    assert set_cell_size("👩\u200d🔧", 1) == " "
+
+
+def test_chop_cells_edge_cases() -> None:
+    """chop_cells for empty strings, ZWJ sequences, and mixed CJK boundaries."""
+    assert chop_cells("", 3) == []
+    assert chop_cells("👩\u200d🔧", 2) == ["👩\u200d🔧"]
+    assert chop_cells("👩\u200d🔧👩\u200d🔧", 2) == ["👩\u200d🔧", "👩\u200d🔧"]
+    assert chop_cells("あ1り2", 3) == ["あ1", "り2"]
+    assert chop_cells("あ1り2", 6) == ["あ1り2"]