cpython: e295ad9be16d (original) (raw)

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changeset 94716:e295ad9be16d 3.4

Issues #814253, #9179: Warnings now are raised when group references and conditional group references are used in lookbehind assertions in regular expressions. [#814253]

Serhiy Storchaka storchaka@gmail.com
date	Sat, 21 Feb 2015 12:08:52 +0200
parents	4dc8b7ed8973
children	a291916333ee 1628484c9408
files	Doc/library/re.rst Lib/sre_parse.py Lib/test/test_re.py Misc/NEWS
diffstat	4 files changed, 61 insertions(+), 3 deletions(-)[+] [-] Doc/library/re.rst 7 Lib/sre_parse.py 20 Lib/test/test_re.py 33 Misc/NEWS 4

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--- a/Doc/library/re.rst +++ b/Doc/library/re.rst @@ -281,7 +281,9 @@ The special characters are: assertion`. (?<=abc)def will find a match in abcdef, since the lookbehind will back up 3 characters and check if the contained pattern matches. The contained pattern must only match strings of some fixed length, meaning that

abc or a|b are allowed, but a* and a{3,4} are not. Note that

abc or a|b are allowed, but a* and a{3,4} are not. Group
references are not supported even if they match strings of some fixed length.
Note that patterns which start with positive lookbehind assertions will not match at the beginning of the string being searched; you will most likely want to use the :func:search function rather than the :func:match function: @@ -301,7 +303,8 @@ The special characters are: Matches if the current position in the string is not preceded by a match for .... This is called a :dfn:negative lookbehind assertion. Similar to positive lookbehind assertions, the contained pattern must only match strings of

some fixed length. Patterns which start with negative lookbehind assertions may

some fixed length and shouldn't contain group references.
Patterns which start with negative lookbehind assertions may match at the beginning of the string being searched.

(?(id/name)yes-pattern|no-pattern)

--- a/Lib/sre_parse.py +++ b/Lib/sre_parse.py @@ -69,6 +69,8 @@ class Pattern: self.open = [] self.groups = 1 self.groupdict = {}

```
   self.lookbehind = 0[](#l2.7)
```

+ def opengroup(self, name=None): gid = self.groups self.groups = gid + 1 @@ -352,6 +354,11 @@ def _escape(source, escape, state): if group < state.groups: if not state.checkgroup(group): raise error("cannot refer to open group")

           if state.lookbehind:[](#l2.16)

               import warnings[](#l2.17)

               warnings.warn('group references in lookbehind '[](#l2.18)

                             'assertions are not supported',[](#l2.19)

                             RuntimeWarning)[](#l2.20)
           return GROUPREF, group[](#l2.21)
       raise ValueError[](#l2.22)
   if len(escape) == 2:[](#l2.23)

@@ -630,6 +637,11 @@ def _parse(source, state): if gid is None: msg = "unknown group name: {0!r}".format(name) raise error(msg)

                   if state.lookbehind:[](#l2.28)

                       import warnings[](#l2.29)

                       warnings.warn('group references in lookbehind '[](#l2.30)

                                     'assertions are not supported',[](#l2.31)

                                     RuntimeWarning)[](#l2.32)
                   subpatternappend((GROUPREF, gid))[](#l2.33)
                   continue[](#l2.34)
               else:[](#l2.35)

@@ -658,7 +670,10 @@ def _parse(source, state): raise error("syntax error") dir = -1 # lookbehind char = sourceget()

                   state.lookbehind += 1[](#l2.40)
               p = _parse_sub(source, state)[](#l2.41)

```
               if dir < 0:[](#l2.42)
```

                   state.lookbehind -= 1[](#l2.43)
               if not sourcematch(")"):[](#l2.44)
                   raise error("unbalanced parenthesis")[](#l2.45)
               if char == "=":[](#l2.46)

@@ -689,6 +704,11 @@ def _parse(source, state): condgroup = int(condname) except ValueError: raise error("bad character in group name")

               if state.lookbehind:[](#l2.51)

                   import warnings[](#l2.52)

                   warnings.warn('group references in lookbehind '[](#l2.53)

                                 'assertions are not supported',[](#l2.54)

                                 RuntimeWarning)[](#l2.55)
           else:[](#l2.56)
               # flags[](#l2.57)
               if not source.next in FLAGS:[](#l2.58)

--- a/Lib/test/test_re.py +++ b/Lib/test/test_re.py @@ -557,7 +557,7 @@ class ReTests(unittest.TestCase): self.assertEqual(re.match("a.*b", "a\n\nb", re.DOTALL).group(0), "a\n\nb")

def test_non_consuming(self):

def test_lookahead(self): self.assertEqual(re.match("(a(?=\s[^a]))", "a b").group(1), "a") self.assertEqual(re.match("(a(?=\s[^a]*))", "a b").group(1), "a") self.assertEqual(re.match("(a(?=\s[abc]))", "a b").group(1), "a")

@@ -571,6 +571,37 @@ class ReTests(unittest.TestCase): self.assertEqual(re.match(r"(a)(?!\s\1)", "a b").group(1), "a") self.assertEqual(re.match(r"(a)(?!\s(abc|a))", "a b").group(1), "a")

```
   # Group reference.[](#l3.16)
```

   self.assertTrue(re.match(r'(a)b(?=\1)a', 'aba'))[](#l3.17)

   self.assertIsNone(re.match(r'(a)b(?=\1)c', 'abac'))[](#l3.18)

```
   # Named group reference.[](#l3.19)
```

   self.assertTrue(re.match(r'(?P<g>a)b(?=(?P=g))a', 'aba'))[](#l3.20)

   self.assertIsNone(re.match(r'(?P<g>a)b(?=(?P=g))c', 'abac'))[](#l3.21)

   # Conditional group reference.[](#l3.22)

   self.assertTrue(re.match(r'(?:(a)|(x))b(?=(?(2)x|c))c', 'abc'))[](#l3.23)

   self.assertIsNone(re.match(r'(?:(a)|(x))b(?=(?(2)c|x))c', 'abc'))[](#l3.24)

   self.assertTrue(re.match(r'(?:(a)|(x))b(?=(?(2)x|c))c', 'abc'))[](#l3.25)

   self.assertIsNone(re.match(r'(?:(a)|(x))b(?=(?(1)b|x))c', 'abc'))[](#l3.26)

   self.assertTrue(re.match(r'(?:(a)|(x))b(?=(?(1)c|x))c', 'abc'))[](#l3.27)

   # Group used before defined.[](#l3.28)

   self.assertTrue(re.match(r'(a)b(?=(?(2)x|c))(c)', 'abc'))[](#l3.29)

   self.assertIsNone(re.match(r'(a)b(?=(?(2)b|x))(c)', 'abc'))[](#l3.30)

   self.assertTrue(re.match(r'(a)b(?=(?(1)c|x))(c)', 'abc'))[](#l3.31)

def test_lookbehind(self):

   self.assertTrue(re.match(r'ab(?<=b)c', 'abc'))[](#l3.34)

   self.assertIsNone(re.match(r'ab(?<=c)c', 'abc'))[](#l3.35)

   self.assertIsNone(re.match(r'ab(?<!b)c', 'abc'))[](#l3.36)

   self.assertTrue(re.match(r'ab(?<!c)c', 'abc'))[](#l3.37)

```
   # Group reference.[](#l3.38)
```

   self.assertWarns(RuntimeWarning, re.compile, r'(a)a(?<=\1)c')[](#l3.39)

```
   # Named group reference.[](#l3.40)
```

   self.assertWarns(RuntimeWarning, re.compile, r'(?P<g>a)a(?<=(?P=g))c')[](#l3.41)

   # Conditional group reference.[](#l3.42)

   self.assertWarns(RuntimeWarning, re.compile, r'(a)b(?<=(?(1)b|x))c')[](#l3.43)

   # Group used before defined.[](#l3.44)

   self.assertWarns(RuntimeWarning, re.compile, r'(a)b(?<=(?(2)b|x))(c)')[](#l3.45)

+ def test_ignore_case(self): self.assertEqual(re.match("abc", "ABC", re.I).group(0), "ABC") self.assertEqual(re.match(b"abc", b"ABC", re.I).group(0), b"ABC")

--- a/Misc/NEWS +++ b/Misc/NEWS @@ -13,6 +13,10 @@ Core and Builtins Library ------- +- Issues #814253, #9179: Warnings now are raised when group references and

conditional group references are used in lookbehind assertions in regular
expressions. +

Issue #23215: Multibyte codecs with custom error handlers that ignores errors consumed too much memory and raised SystemError or MemoryError. Original patch by Aleksi Torhamo.