[3.7] bpo-35168: Make shlex.punctuation_chars read-only (GH-11631) (GH-15926)

(cherry picked from commit 972cf5c) Co-authored-by: Alex <a.v.shkop@gmail.com>

Author: vsajip

Doc/library/shlex.rst

@@ -98,7 +98,9 @@ The :mod:`shlex` module defines the following class:
  characters, those characters will be used as the punctuation characters. Any
  characters in the :attr:`wordchars` attribute that appear in
  *punctuation_chars* will be removed from :attr:`wordchars`. See
- :ref:`improved-shell-compatibility` for more information.
+ :ref:`improved-shell-compatibility` for more information. *punctuation_chars*
+ can be set only upon :class:`~shlex.shlex` instance creation and can't be
+ modified later.
 
  .. versionchanged:: 3.6
  The *punctuation_chars* parameter was added.
@@ -299,8 +301,8 @@ variables which either control lexical analysis or can be used for debugging:
 
 .. attribute:: shlex.punctuation_chars
 
- Characters that will be considered punctuation. Runs of punctuation
- characters will be returned as a single token. However, note that no
+ A read-only property. Characters that will be considered punctuation. Runs of
+ punctuation characters will be returned as a single token. However, note that no
  semantic validity checking will be performed: for example, '>>>' could be
  returned as a token, even though it may not be recognised as such by shells.
 

Lib/shlex.py

@@ -55,7 +55,7 @@ def __init__(self, instream=None, infile=None, posix=False,
  punctuation_chars = ''
  elif punctuation_chars is True:
  punctuation_chars = '();<>|&'
- self.punctuation_chars = punctuation_chars
+ self._punctuation_chars = punctuation_chars
  if punctuation_chars:
  # _pushback_chars is a push back queue used by lookahead logic
  self._pushback_chars = deque()
@@ -65,6 +65,10 @@ def __init__(self, instream=None, infile=None, posix=False,
  t = self.wordchars.maketrans(dict.fromkeys(punctuation_chars))
  self.wordchars = self.wordchars.translate(t)
 
+ @property
+ def punctuation_chars(self):
+ return self._punctuation_chars
+
  def push_token(self, tok):
  "Push a token onto the stack popped by the get_token method"
  if self.debug >= 1:

Lib/test/test_shlex.py

@@ -308,6 +308,14 @@ def testQuote(self):
  self.assertEqual(shlex.quote("test%s'name'" % u),
  "'test%s'\"'\"'name'\"'\"''" % u)
 
+ def testPunctuationCharsReadOnly(self):
+ punctuation_chars = "/|$%^"
+ shlex_instance = shlex.shlex(punctuation_chars=punctuation_chars)
+ self.assertEqual(shlex_instance.punctuation_chars, punctuation_chars)
+ with self.assertRaises(AttributeError):
+ shlex_instance.punctuation_chars = False
+
+
 # Allow this test to be used with old shlex.py
 if not getattr(shlex, "split", None):
  for methname in dir(ShlexTest):

Misc/NEWS.d/next/Library/2019-01-22-09-23-20.bpo-35168.UGv2yW.rst

@@ -0,0 +1 @@
+:attr:`shlex.shlex.punctuation_chars` is now a read-only property.