pantsbuild / pants / 26612973470

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fix: fallback to default width when terminal size is 0 (#23364)

Resolves #17946

# Problem Description
The bug occurred specifically when running help commands (pants help)
within the Emacs editor's eshell terminal. Because it is a more limited
environment, eshell incorrectly reported the terminal width as 0
columns.

The function responsible for calculating this width (terminal_width),
located in the docutil.py file, used the shutil.get_terminal_size()
method to capture the value. Upon receiving the value 0, the function
simply subtracted a standard padding of 2. This mathematical calculation
resulted in a negative width of -2. Consequently, when the system
attempted to format the help text to fit on an impossible -2 column
screen, the program suffered a total collapse, triggering the fatal
error ValueError: invalid width -2 (must be > 0).

# What changed
Refactored terminal_width in docutil.py to explicitly check if
shutil.get_terminal_size().columns returns 0.

If columns == 0 (which happens in limited terminals like Emacs eshell),
the function now applies the default fallback value before subtracting
the padding, preventing a ValueError with negative widths.

Added a regression test
(test_terminal_width_falls_back_when_columns_are_zero) in
docutil_test.py to ensure the fallback logic holds via monkeypatching.

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93070 of 100299 relevant lines covered (92.79%)

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