an SRE bugfix a day keeps Guido away...

#462270: sub-tle difference between pre.sub and sre.sub.  PRE ignored
an empty match at the previous location, SRE didn't.

also synced with Secret Labs "sreopen" codebase.

Lib/sre.py

@@ -45,7 +45,7 @@ The special characters are:
     "|"      A|B, creates an RE that will match either A or B.
     (...)    Matches the RE inside the parentheses.
              The contents can be retrieved or matched later in the string.
-    (?iLmsx) Set the I, L, M, S, or X flag for the RE.
+    (?iLmsx) Set the I, L, M, S, or X flag for the RE (see below).
     (?:...)  Non-grouping version of regular parentheses.
     (?P<name>...) The substring matched by the group is accessible by name.
     (?P=name)     Matches the text matched earlier by the group named name.
@@ -80,7 +80,6 @@ This module exports the following functions:
     findall  Find all occurrences of a pattern in a string.
     compile  Compile a pattern into a RegexObject.
     purge    Clear the regular expression cache.
-    template Compile a template pattern, returning a pattern object.
     escape   Backslash all non-alphanumerics in a string.
 
 Some of the functions in this module takes flags as optional parameters:
@@ -90,11 +89,12 @@ Some of the functions in this module takes flags as optional parameters:
                    "$" matches the end of lines as well as the string.
     S  DOTALL      "." matches any character at all, including the newline.
     X  VERBOSE     Ignore whitespace and comments for nicer looking RE's.
-    U  UNICODE     Use unicode locale.
+    U  UNICODE     Make \w, \W, \b, \B, dependent on the Unicode locale.
 
 This module also defines an exception 'error'.
 
 """
+
 import sre_compile
 import sre_parse
 
@@ -104,7 +104,7 @@ __all__ = [ "match", "search", "sub", "subn", "split", "findall",
     "U", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",
     "UNICODE", "error" ]
 
-__version__ = "2.1b2"
+__version__ = "2.1.1"
 
 # this module works under 1.5.2 and later.  don't use string methods
 import string
@@ -269,6 +269,9 @@ def _subn(pattern, template, text, count=0, sub=0):
         b, e = m.span()
         if i < b:
             append(text[i:b])
+        elif i == b == e and n:
+            append(text[i:b])
+            continue # ignore empty match at previous position
         append(filter(m))
         i = e
         n = n + 1

Lib/test/test_sre.py

@@ -123,6 +123,10 @@ test(r"""sre.sub('\r\n', r'\n', 'abc\r\ndef\r\n')""", 'abc\ndef\n')
 test(r"""sre.sub(r'\r\n', '\n', 'abc\r\ndef\r\n')""", 'abc\ndef\n')
 test(r"""sre.sub('\r\n', '\n', 'abc\r\ndef\r\n')""", 'abc\ndef\n')
 
+# Test for empty sub() behaviour, see SF bug #462270
+test(r"""sre.sub('x*', '-', 'abxd')""", '-a-b-d-')
+test(r"""sre.sub('x+', '-', 'abxd')""", 'ab-d')
+
 if verbose:
     print 'Running tests on symbolic references'
 

Modules/_sre.c

@@ -31,6 +31,7 @@
  * 2001-04-28 fl  added __copy__ methods (work in progress)
  * 2001-05-14 fl  fixes for 1.5.2
  * 2001-07-01 fl  added BIGCHARSET support (from Martin von Loewis)
+ * 2001-09-18 fl  
  *
  * Copyright (c) 1997-2001 by Secret Labs AB.  All rights reserved.
  *
@@ -133,6 +134,8 @@ static char copyright[] =
 #define SRE_ALNUM_MASK 8
 #define SRE_WORD_MASK 16
 
+/* FIXME: this assumes ASCII.  create tables in init_sre() instead */
+
 static char sre_char_info[128] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 6, 2,
 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 25, 25, 25, 25, 25, 25, 25, 25,
@@ -1141,6 +1144,7 @@ SRE_MATCH(SRE_STATE* state, SRE_CODE* pattern, int level)
     }
 
     /* can't end up here */
+    /* return SRE_ERROR_ILLEGAL; -- see python-dev discussion */
 }
 
 LOCAL(int)
@@ -2624,16 +2628,17 @@ init_sre(void)
     m = Py_InitModule("_" SRE_MODULE, _functions);
     d = PyModule_GetDict(m);
 
-    PyDict_SetItemString(
-        d, "MAGIC", (x = (PyObject*) PyInt_FromLong(SRE_MAGIC))
-        );
-    Py_XDECREF(x);
-
-    PyDict_SetItemString(
-	d, "copyright", (x = (PyObject*)PyString_FromString(copyright))
-        );
-    Py_XDECREF(x);
+    x = PyInt_FromLong(SRE_MAGIC);
+    if (x) {
+        PyDict_SetItemString(d, "MAGIC", x);
+        Py_DECREF(x);
+    }
 
+    x = PyString_FromString(copyright);
+    if (x) {
+        PyDict_SetItemString(d, "copyright", x);
+        Py_DECREF(x);
+    }
 }
 
 #endif /* !defined(SRE_RECURSIVE) */