bugfix: IndexError when 'n' exceeds length

docs/intro.rst

@@ -654,6 +654,10 @@ languages:
 History
 =======
 
+0.8.2 *2026-06-29*
+  * **Bugfix** Do not raise IndexError when given legacy POSIX ``n`` argument to `wcswidth()`_ or
+    `wcstwidth()`_ exceed string length without raising IndexError
+
 0.8.1 *2026-06-08*
   * **Improved** `wcstwidth()`_ with new ``zeroer``, ``narrow_wider``, and ``narrow_zeroer``
     Corrections_. `PR #226`_

pyproject.toml

@@ -4,7 +4,7 @@ requires = [ "hatchling" ]
 
 [project]
 name = "wcwidth"
-version = "0.8.1"  # don't forget to also update wcwidth/__init__.py:__version__
+version = "0.8.2"  # don't forget to also update wcwidth/__init__.py:__version__
 description = "Measures the displayed width of unicode strings in a terminal"
 readme = "README.rst"
 keywords = [

tests/test_core.py

@@ -497,6 +497,12 @@ def test_zwj_at_end_of_string():
     assert wcwidth.wcswidth('a\u200D') == 1
 
 
+def test_wcswidth_n_exceeds_length():
+    """Verify wcswidth() with n > len(string) does not raise IndexError."""
+    assert wcwidth.wcswidth('hello', n=999) == 5
+    assert wcwidth.wcswidth('\u30B3\u30F3', n=999) == 4
+
+
 def test_soft_hyphen():
     # Test SOFT HYPHEN, category 'Cf' usually are zero-width, but most
     # implementations agree to draw it was '1' cell, visually

tests/test_term_overrides.py

@@ -418,6 +418,13 @@ def test_get_term_overrides_narrow_wider_still_empty():
     assert overrides.narrow_wider == ()
 
 
+@pytest.mark.parametrize('func', [wcwidth.wcstwidth, wcwidth.width])
+def test_narrow_wider_width(func):
+    """Verify width() & wcstwidth() match result of narrow_wider overrides."""
+    assert wcwidth.wcswidth('\u261d') == 1
+    assert func('\u261d', term_program='kitty') == 2
+
+
 @pytest.mark.parametrize('codepoint', [
     '\u00ad',
     '\u0600',

wcwidth/__init__.py

@@ -78,4 +78,4 @@
 # Using 'hatchling', it does not seem to provide the pyproject.toml nicety, "dynamic = ['version']"
 # like flit_core, maybe there is some better way but for now we have to duplicate it in both places
 # Prefer the installed distribution version when available (helps test environments)
-__version__ = '0.8.1'  # don't forget to also update pyproject.toml:version
+__version__ = '0.8.2'  # don't forget to also update pyproject.toml:version

wcwidth/_wcswidth.py

@@ -98,7 +98,7 @@ def wcswidth(
 
     _wcwidth = wcwidth if ambiguous_width == 1 else lambda c: wcwidth(c, 'auto', ambiguous_width)
 
-    end = len(pwcs) if n is None else n
+    end = len(pwcs) if n is None else min(n, len(pwcs))
     total_width = 0
     idx = 0
 
@@ -262,7 +262,7 @@ def wcstwidth(
     # Select wcwidth call pattern for best lru_cache performance
     _wcwidth = wcwidth if ambiguous_width == 1 else lambda c: wcwidth(c, 'auto', ambiguous_width)
 
-    end = len(pwcs) if n is None else n
+    end = len(pwcs) if n is None else min(n, len(pwcs))
     total_width = 0
     idx = 0