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Degrade to identity on a malformed transform substring instead of raising ValueError #247

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eeshsaxena wants to merge 1 commit into from
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Degrade to identity on a malformed transform substring instead of raising ValueError #247

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18 changes: 15 additions & 3 deletions svgpathtools/parser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,11 +30,23 @@ def _check_num_parsed_values(values, allowed):

def _parse_transform_substr(transform_substr):

transform = np.identity(3)

# A well-formed transform substring is `type(v1 v2 ...)`. Malformed input
# (no/extra parenthesis, or non-numeric values) previously raised a bare
# ValueError; degrade to the identity matrix with a warning, like the
# unknown-type and wrong-argument-count cases below.
if transform_substr.count('(') != 1:
warnings.warn('Invalid SVG transform substring: {0}'.format(transform_substr))
return transform

type_str, value_str = transform_substr.split('(')
value_str = value_str.replace(',', ' ')
values = list(map(float, filter(None, value_str.split(' '))))

transform = np.identity(3)
try:
values = list(map(float, filter(None, value_str.split(' '))))

@mathandy mathandy Aug 26, 2026

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Suggested change
values = list(map(float, filter(None, value_str.split(' '))))
values = [float(s) for s in value_str.split()]

A bit easier to read (IMO) and robust against other/multiple whitespace chars.

except ValueError:
warnings.warn('Invalid SVG transform substring: {0}'.format(transform_substr))
return transform
if 'matrix' in type_str:
if not _check_num_parsed_values(values, [6]):
return transform
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13 changes: 13 additions & 0 deletions test/test_parsing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -249,6 +249,19 @@ def test_transform(self):
scale(10 0.5)""")
))

def test_transform_malformed(self):
# Malformed transform substrings (non-numeric values, missing or extra
# parentheses) used to raise a bare ValueError; they should degrade to
# the identity matrix like the unknown-type case.
import warnings
identity = np.identity(3)
for bad in ('matrix(1 x 3 4 5 6)', 'translate(a)', 'scale()',
'rotate(1 2 z)', 'foo(1', 'matrix'):
with warnings.catch_warnings():
warnings.simplefilter('ignore')
tf = svgpathtools.parser.parse_transform(bad)
self.assertTrue(np.array_equal(identity, tf))

def test_pathd_init(self):
path0 = Path('')
path1 = parse_path("M 100 100 L 300 100 L 200 300 z")
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