From a4a13a7930898bc5c61a019d3870384633ed3d16 Mon Sep 17 00:00:00 2001
From: Pitchfork-and-Torch <pitchfork-and-torch@users.noreply.github.com>
Date: Fri, 18 Sep 2026 03:17:21 +0000
Subject: [PATCH] Reject bool/float/nan in maxcolwidths

bool is an int subclass, so maxcolwidths=True previously wrapped every
character. float('nan') bypassed the width<=0 guard (NaN comparisons are
false) and hung forever inside textwrap. Require positive ints or None.
---
 tabulate/__init__.py    | 20 ++++++++++++++++++++
 test/test_regression.py | 21 ++++++++++++++++++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/tabulate/__init__.py b/tabulate/__init__.py
index 12a2950..6fa0dca 100644
--- a/tabulate/__init__.py
+++ b/tabulate/__init__.py
@@ -1613,6 +1613,25 @@ def _normalize_tabular_data(tabular_data, headers, showindex="default"):
     return rows, headers, headers_pad
 
 
+def _validate_maxcolwidth(width):
+    """Return a positive int column width, or None to leave the column unbound.
+
+    ``bool`` is rejected (it is an ``int`` subclass): ``True`` previously wrapped
+    every character. Non-ints — including ``float('nan')`` — are rejected too;
+    ``nan`` bypassed ``width <= 0`` (comparisons with NaN are false) and hung
+    inside ``textwrap`` forever.
+    """
+    if width is None:
+        return None
+    if isinstance(width, bool) or not isinstance(width, int):
+        raise TypeError(
+            f"maxcolwidths values must be positive ints or None, got {width!r}"
+        )
+    if width <= 0:
+        raise ValueError(f"invalid width {width!r} (must be > 0)")
+    return width
+
+
 def _wrap_text_to_colwidths(
     list_of_lists,
     colwidths,
@@ -1636,6 +1655,7 @@ def _wrap_text_to_colwidths(
                 new_row.append(cell)
                 continue
 
+            width = _validate_maxcolwidth(width)
             if width is not None:
                 wrapper = _CustomTextWrap(
                     width=width,
diff --git a/test/test_regression.py b/test/test_regression.py
index 9555676..c0911f4 100644
--- a/test/test_regression.py
+++ b/test/test_regression.py
@@ -2,7 +2,7 @@
 
 from tabulate import DataRow, Line, TableFormat, tabulate
 
-from common import assert_equal, skip
+from common import assert_equal, raises, skip
 
 
 def test_ansi_color_in_table_cells():
@@ -598,3 +598,22 @@ def test_github_escape_pipe_character():
     result = tabulate([["foo|bar"]], headers=("spam|eggs",), tablefmt="github")
     expected = "| spam\\|eggs   |\n|:------------|\n| foo\\|bar     |"
     assert_equal(expected, result)
+
+def test_maxcolwidths_rejects_bool_float_nan():
+    "maxcolwidths: reject bool/float/nan (bool wrapped every char; nan hung)"
+    import math
+
+    for bad in (True, [True], [0.5], [float("nan")], [math.inf]):
+        try:
+            tabulate([["hello"]], maxcolwidths=bad)
+            raise AssertionError(f"expected TypeError for {bad!r}")
+        except TypeError:
+            pass
+    try:
+        tabulate([["hello"]], maxcolwidths=[-1])
+        raise AssertionError("expected ValueError for -1")
+    except ValueError:
+        pass
+    # None still means unbound
+    result = tabulate([["hello"]], maxcolwidths=[None], tablefmt="plain")
+    assert_equal("hello", result)