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gh-116957: configparser: Do post-process values after DuplicateOption…
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…Error (GH-116958)

If you catch DuplicateOptionError / DuplicateSectionError when reading a
config file (the intention is to skip invalid config files) and then
attempt to use the ConfigParser instance, any values it *had* read
successfully so far, were stored as a list instead of string! Later
`get` calls would raise "AttributeError: 'list' object has no attribute
'find'" from somewhere deep in the interpolation code.
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@drothlis
drothlis committed Mar 19, 2024
1 parent a8e93d3 commit b1bc375
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184 changes: 93 additions & 91 deletions Lib/configparser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -961,102 +961,104 @@ def _read(self, fp, fpname):
lineno = 0
indent_level = 0
e = None # None, or an exception
for lineno, line in enumerate(fp, start=1):
comment_start = sys.maxsize
# strip inline comments
inline_prefixes = {p: -1 for p in self._inline_comment_prefixes}
while comment_start == sys.maxsize and inline_prefixes:
next_prefixes = {}
for prefix, index in inline_prefixes.items():
index = line.find(prefix, index+1)
if index == -1:
continue
next_prefixes[prefix] = index
if index == 0 or (index > 0 and line[index-1].isspace()):
comment_start = min(comment_start, index)
inline_prefixes = next_prefixes
# strip full line comments
for prefix in self._comment_prefixes:
if line.strip().startswith(prefix):
comment_start = 0
break
if comment_start == sys.maxsize:
comment_start = None
value = line[:comment_start].strip()
if not value:
if self._empty_lines_in_values:
# add empty line to the value, but only if there was no
# comment on the line
if (comment_start is None and
cursect is not None and
optname and
cursect[optname] is not None):
cursect[optname].append('') # newlines added at join
else:
# empty line marks end of value
indent_level = sys.maxsize
continue
# continuation line?
first_nonspace = self.NONSPACECRE.search(line)
cur_indent_level = first_nonspace.start() if first_nonspace else 0
if (cursect is not None and optname and
cur_indent_level > indent_level):
if cursect[optname] is None:
raise MultilineContinuationError(fpname, lineno, line)
cursect[optname].append(value)
# a section header or option header?
else:
indent_level = cur_indent_level
# is it a section header?
mo = self.SECTCRE.match(value)
if mo:
sectname = mo.group('header')
if sectname in self._sections:
if self._strict and sectname in elements_added:
raise DuplicateSectionError(sectname, fpname,
lineno)
cursect = self._sections[sectname]
elements_added.add(sectname)
elif sectname == self.default_section:
cursect = self._defaults
try:
for lineno, line in enumerate(fp, start=1):
comment_start = sys.maxsize
# strip inline comments
inline_prefixes = {p: -1 for p in self._inline_comment_prefixes}
while comment_start == sys.maxsize and inline_prefixes:
next_prefixes = {}
for prefix, index in inline_prefixes.items():
index = line.find(prefix, index+1)
if index == -1:
continue
next_prefixes[prefix] = index
if index == 0 or (index > 0 and line[index-1].isspace()):
comment_start = min(comment_start, index)
inline_prefixes = next_prefixes
# strip full line comments
for prefix in self._comment_prefixes:
if line.strip().startswith(prefix):
comment_start = 0
break
if comment_start == sys.maxsize:
comment_start = None
value = line[:comment_start].strip()
if not value:
if self._empty_lines_in_values:
# add empty line to the value, but only if there was no
# comment on the line
if (comment_start is None and
cursect is not None and
optname and
cursect[optname] is not None):
cursect[optname].append('') # newlines added at join
else:
cursect = self._dict()
self._sections[sectname] = cursect
self._proxies[sectname] = SectionProxy(self, sectname)
elements_added.add(sectname)
# So sections can't start with a continuation line
optname = None
# no section header in the file?
elif cursect is None:
raise MissingSectionHeaderError(fpname, lineno, line)
# an option line?
# empty line marks end of value
indent_level = sys.maxsize
continue
# continuation line?
first_nonspace = self.NONSPACECRE.search(line)
cur_indent_level = first_nonspace.start() if first_nonspace else 0
if (cursect is not None and optname and
cur_indent_level > indent_level):
if cursect[optname] is None:
raise MultilineContinuationError(fpname, lineno, line)
cursect[optname].append(value)
# a section header or option header?
else:
mo = self._optcre.match(value)
indent_level = cur_indent_level
# is it a section header?
mo = self.SECTCRE.match(value)
if mo:
optname, vi, optval = mo.group('option', 'vi', 'value')
if not optname:
e = self._handle_error(e, fpname, lineno, line)
optname = self.optionxform(optname.rstrip())
if (self._strict and
(sectname, optname) in elements_added):
raise DuplicateOptionError(sectname, optname,
fpname, lineno)
elements_added.add((sectname, optname))
# This check is fine because the OPTCRE cannot
# match if it would set optval to None
if optval is not None:
optval = optval.strip()
cursect[optname] = [optval]
sectname = mo.group('header')
if sectname in self._sections:
if self._strict and sectname in elements_added:
raise DuplicateSectionError(sectname, fpname,
lineno)
cursect = self._sections[sectname]
elements_added.add(sectname)
elif sectname == self.default_section:
cursect = self._defaults
else:
# valueless option handling
cursect[optname] = None
cursect = self._dict()
self._sections[sectname] = cursect
self._proxies[sectname] = SectionProxy(self, sectname)
elements_added.add(sectname)
# So sections can't start with a continuation line
optname = None
# no section header in the file?
elif cursect is None:
raise MissingSectionHeaderError(fpname, lineno, line)
# an option line?
else:
# a non-fatal parsing error occurred. set up the
# exception but keep going. the exception will be
# raised at the end of the file and will contain a
# list of all bogus lines
e = self._handle_error(e, fpname, lineno, line)
self._join_multiline_values()
mo = self._optcre.match(value)
if mo:
optname, vi, optval = mo.group('option', 'vi', 'value')
if not optname:
e = self._handle_error(e, fpname, lineno, line)
optname = self.optionxform(optname.rstrip())
if (self._strict and
(sectname, optname) in elements_added):
raise DuplicateOptionError(sectname, optname,
fpname, lineno)
elements_added.add((sectname, optname))
# This check is fine because the OPTCRE cannot
# match if it would set optval to None
if optval is not None:
optval = optval.strip()
cursect[optname] = [optval]
else:
# valueless option handling
cursect[optname] = None
else:
# a non-fatal parsing error occurred. set up the
# exception but keep going. the exception will be
# raised at the end of the file and will contain a
# list of all bogus lines
e = self._handle_error(e, fpname, lineno, line)
finally:
self._join_multiline_values()
# if any parsing errors occurred, raise an exception
if e:
raise e
Expand Down
15 changes: 15 additions & 0 deletions Lib/test/test_configparser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -646,6 +646,21 @@ def test_weird_errors(self):
"'opt' in section 'Bar' already exists")
self.assertEqual(e.args, ("Bar", "opt", "<dict>", None))

def test_get_after_duplicate_option_error(self):
cf = self.newconfig()
ini = textwrap.dedent("""\
[Foo]
x{equals}1
y{equals}2
y{equals}3
""".format(equals=self.delimiters[0]))
if self.strict:
with self.assertRaises(configparser.DuplicateOptionError):
cf.read_string(ini)
else:
cf.read_string(ini)
self.assertEqual(cf.get('Foo', 'x'), '1')

def test_write(self):
config_string = (
"[Long Line]\n"
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2024-03-18-14-36-50.gh-issue-116957.dTCs4f.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
configparser: Don't leave ConfigParser values in an invalid state (stored as
a list instead of a str) after an earlier read raised DuplicateSectionError
or DuplicateOptionError.

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