Fixed ZeroDivisionError in async_alert() when shutil.get_terminal_size().columns returned 0.

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 2.5.4 (TBD)
+* Bug Fixes
+  * Fixed `ZeroDivisionError` in `async_alert()` when `shutil.get_terminal_size().columns`
+    returned 0.
+
 ## 2.5.3 (November 5, 2024)
 * Enhancements
   * Changed `CommandSet._cmd` to a read-only property which never returns `None` because it

cmd2/cmd2.py

@@ -5335,9 +5335,12 @@ def async_alert(self, alert_msg: str, new_prompt: Optional[str] = None) -> None:
             if update_terminal:
                 import shutil
 
+                # Prior to Python 3.11 this can return 0, so use a fallback if needed.
+                terminal_columns = shutil.get_terminal_size().columns or constants.DEFAULT_TERMINAL_WIDTH
+
                 # Print a string which replaces the onscreen prompt and input lines with the alert.
                 terminal_str = ansi.async_alert_str(
-                    terminal_columns=shutil.get_terminal_size().columns,
+                    terminal_columns=terminal_columns,
                     prompt=rl_get_display_prompt(),
                     line=readline.get_line_buffer(),
                     cursor_offset=rl_get_point(),

cmd2/constants.py

@@ -57,3 +57,6 @@
 
 # custom attributes added to argparse Namespaces
 NS_ATTR_SUBCMD_HANDLER = '__subcmd_handler__'
+
+# For cases prior to Python 3.11 when shutil.get_terminal_size().columns can return 0.
+DEFAULT_TERMINAL_WIDTH = 80

cmd2/utils.py

@@ -874,7 +874,8 @@ def align_text(
     )
 
     if width is None:
-        width = shutil.get_terminal_size().columns
+        # Prior to Python 3.11 this can return 0, so use a fallback if needed.
+        width = shutil.get_terminal_size().columns or constants.DEFAULT_TERMINAL_WIDTH
 
     if width < 1:
         raise ValueError("width must be at least 1")

tests/test_utils.py

@@ -17,6 +17,7 @@
 import cmd2.utils as cu
 from cmd2 import (
     ansi,
+    constants,
 )
 from cmd2.constants import (
     HORIZONTAL_ELLIPSIS,
@@ -624,7 +625,9 @@ def test_align_text_term_width():
     text = 'foo'
     fill_char = ' '
 
-    term_width = shutil.get_terminal_size().columns
+    # Prior to Python 3.11 this can return 0, so use a fallback, so
+    # use the same fallback that cu.align_text() does if needed.
+    term_width = shutil.get_terminal_size().columns or constants.DEFAULT_TERMINAL_WIDTH
     expected_fill = (term_width - ansi.style_aware_wcswidth(text)) * fill_char
 
     aligned = cu.align_text(text, cu.TextAlignment.LEFT, fill_char=fill_char)