fix: crash on backslash-continuation where import is on the second line - #354
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``FilterMultilineImport.__init__`` assumed that the first line always
contains the ``import`` keyword and therefore that ``IMPORT_RE.split()``
always returns two parts. For the valid Python pattern
from very.long.module.path \
import SomeName, OtherName
the first line has no ``import``, so the split returned a one-element
list and Python raised ``ValueError: not enough values to unpack``.
Fix by detecting the one-element split, storing the whole first line
in ``self.from_`` with ``imports = ""``, and setting ``give_up = True``
so the statement is passed through unchanged. The ``__call__`` give_up
path is also corrected so it does not spuriously insert ``"import "``
into the reconstruction in this case.
Fixes PyCQA#259
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#365) Follow-up to #354. Instead of threading a give-up flag through FilterMultilineImport.__init__ and __call__, skip constructing the filter entirely when the first line has no `import` keyword: the statement can never be filtered, and the class never accumulated any continuation lines in that case anyway (with empty `imports` the pending fix was immediately over). Behavior is unchanged. Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Fixes #259.
Problem
FilterMultilineImport.__init__splits the first line on\bimport\bto separate the
from Xfragment from the imported names. For thevalid Python pattern
the first line contains no
importkeyword, soIMPORT_RE.split(line, maxsplit=1)returns a one-element list.Unpacking that into two variables raised:
Fix
Detect the one-element result, assign
self.from_ = lineandimports = "", and setgive_up = Trueso the entire statement ispassed through unchanged. The
__call__give-up return path is alsofixed so it does not spuriously prepend
"import "in this case.Test
Added
test_filter_code_backslash_continuation_import_on_second_linewhich exercises exactly the pattern from the issue report.
This pull request was prepared with the assistance of AI, under my direction and review.