26613861926

Committed 29 May 2026 02:12AM UTC coverage: 92.891% (-0.001%) from 92.892%

Build # 26613861926

Build Type

push

github

Committed by

web-flow

Commit Message

fix: fallback to default width when terminal size is 0 (Cherry-pick of #23364) (#23385)

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.

Co-authored-by: Thiago Riemma Carbonera <132521983+thiago-carbonera@users.noreply.github.com>

Coverage Stats

9 of 9 new or added lines in 2 files covered. (100.0%)

1 existing line in 1 file now uncovered.

92120 of 99170 relevant lines covered (92.89%)

4.04 hits per line

Source File
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96.15

/src/python/pants/backend/tools/preamble/subsystem.py

# Copyright 2022 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).
from __future__ import annotations

from collections.abc import Sequence

from pants.option.option_types import DictOption, SkipOption
from pants.option.subsystem import Subsystem
from pants.source.filespec import FilespecMatcher
from pants.util.strutil import help_text, softwrap


class PreambleSubsystem(Subsystem):
    options_scope = "preamble"
    name = "preamble"
    help = help_text(
        """
        Formats files with a preamble, with the preamble looked up based on path.

        This is useful for things such as copyright headers or shebang lines.

        Pants substitutes the following identifiers (following Python's `string.Template` substitutions):
        - $year: The current year (only used when actually writing the year to the file).
        """
    )

    skip = SkipOption("fmt")

    _template_by_globs = DictOption[str](
        help=softwrap(
            """
            Which preamble template to use based on the path globs (relative to the build root).

            Example:

                {
                    '*.rs': '// Copyright (c) $year\\n// Line 2\\n'
                    '*.py:!__init__.py': '# Copyright (c) $year\\n# Line 2\\n',
                }

            It might be helpful to load this config from a JSON or YAML file. To do that, set
            `[preamble].config = '@path/to/config.yaml'`, for example.
            """
        ),
        fromfile=True,
    )

    @property
    def template_by_globs(self) -> dict[tuple[str, ...], str]:
        return {tuple(key.split(":")): value for key, value in self._template_by_globs.items()}

    def get_template_by_path(self, filepaths: Sequence[str]) -> dict[str, str]:
        """Returns a mapping from path to (most-relevant) template."""
        filepaths_to_test = set(filepaths)
        template_by_path = {}
        for globs, template in self.template_by_globs.items():
            if not filepaths_to_test:
                break

            matched_filepaths = FilespecMatcher(
                includes=[
                    (glob[2:] if glob.startswith(r"\\!") else glob)
                    for glob in globs
                    if not glob.startswith("!")
                ],
                excludes=[glob[1:] for glob in globs if glob.startswith("!")],
            ).matches(tuple(filepaths_to_test))
            filepaths_to_test -= set(matched_filepaths)
            for filepath in matched_filepaths:
                template_by_path[filepath] = template

        return template_by_path

1	# Copyright 2022 Pants project contributors (see CONTRIBUTORS.md).
2	# Licensed under the Apache License, Version 2.0 (see LICENSE).
3	from __future__ import annotations	1✔
4
5	from collections.abc import Sequence	1✔
6
7	from pants.option.option_types import DictOption, SkipOption	1✔
8	from pants.option.subsystem import Subsystem	1✔
9	from pants.source.filespec import FilespecMatcher	1✔
10	from pants.util.strutil import help_text, softwrap	1✔
11
12
13	class PreambleSubsystem(Subsystem):	1✔
14	options_scope = "preamble"	1✔
15	name = "preamble"	1✔
16	help = help_text(	1✔
17	"""
18	Formats files with a preamble, with the preamble looked up based on path.
19
20	This is useful for things such as copyright headers or shebang lines.
21
22	Pants substitutes the following identifiers (following Python's `string.Template` substitutions):
23	- $year: The current year (only used when actually writing the year to the file).
24	"""
25	)
26
27	skip = SkipOption("fmt")	1✔
28
29	_template_by_globs = DictOption[str](	1✔
30	help=softwrap(
31	"""
32	Which preamble template to use based on the path globs (relative to the build root).
33
34	Example:
35
36	{
37	'*.rs': '// Copyright (c) $year\\n// Line 2\\n'
38	'*.py:!__init__.py': '# Copyright (c) $year\\n# Line 2\\n',
39	}
40
41	It might be helpful to load this config from a JSON or YAML file. To do that, set
42	`[preamble].config = '@path/to/config.yaml'`, for example.
43	"""
44	),
45	fromfile=True,
46	)
47
48	@property	1✔
49	def template_by_globs(self) -> dict[tuple[str, ...], str]:	1✔
50	return {tuple(key.split(":")): value for key, value in self._template_by_globs.items()}	1✔
51
52	def get_template_by_path(self, filepaths: Sequence[str]) -> dict[str, str]:	1✔
53	"""Returns a mapping from path to (most-relevant) template."""
54	filepaths_to_test = set(filepaths)	1✔
55	template_by_path = {}	1✔
56	for globs, template in self.template_by_globs.items():	1✔
57	if not filepaths_to_test:	1✔
UNCOV 58	break	×
59
60	matched_filepaths = FilespecMatcher(	1✔
61	includes=[
62	(glob[2:] if glob.startswith(r"\\!") else glob)
63	for glob in globs
64	if not glob.startswith("!")
65	],
66	excludes=[glob[1:] for glob in globs if glob.startswith("!")],
67	).matches(tuple(filepaths_to_test))
68	filepaths_to_test -= set(matched_filepaths)	1✔
69	for filepath in matched_filepaths:	1✔
70	template_by_path[filepath] = template	1✔
71
72	return template_by_path	1✔

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