smarty: Add back special case for decade abbreviations

The previous version did not work, and was incorrectly removed as part of
85ad180. In the new version, use lookbehind search for \w instead
of \b, so that it works.

Update the tests accordingly.

Fixes Python-Markdown#399 (except parts that we can't fix). Thanks @gandaro for the report.

Author: mitya57

markdown/extensions/smarty.py

@@ -126,6 +126,9 @@
 doubleQuoteSetsRe = r""""'(?=\w)"""
 singleQuoteSetsRe = r"""'"(?=\w)"""
 
+# Special case for decade abbreviations (the '80s):
+decadeAbbrRe = r"(?<!\w)'(?=\d{2}s)"
+
 # Get most opening double quotes:
 openingDoubleQuotesRegex = r'%s"(?=\w)' % openingQuotesBase
 
@@ -227,6 +230,7 @@ def educateQuotes(self, md):
             (doubleQuoteStartRe, (rdquo,)),
             (doubleQuoteSetsRe, (ldquo + lsquo,)),
             (singleQuoteSetsRe, (lsquo + ldquo,)),
+            (decadeAbbrRe, (rsquo,)),
             (openingSingleQuotesRegex, (2, lsquo)),
             (closingSingleQuotesRegex, (rsquo,)),
             (closingSingleQuotesRegex2, (rsquo, 2)),

tests/extensions/smarty.html

@@ -1,11 +1,11 @@
-<p>&rsquo;.
+<p>&rsquo;.<br />
 1440&ndash;80&rsquo;s<br />
-1440&ndash;&lsquo;80s<br />
-1440&mdash;&lsquo;80s<br />
+1440&ndash;&rsquo;80s<br />
+1440&mdash;&rsquo;80s<br />
 1960s<br />
 1960&rsquo;s<br />
-one two &lsquo;60s<br />
-&lsquo;60s</p>
+one two &rsquo;60s<br />
+&rsquo;60s</p>
 <p>It&rsquo;s fun. What&rsquo;s fun?<br />
 &ldquo;Isn&rsquo;t this fun&rdquo;? &mdash; she said&hellip;<br />
 &ldquo;&lsquo;Quoted&rsquo; words in a larger quote.&rdquo;<br />

tests/extensions/smarty.txt

@@ -1,4 +1,4 @@
-'.
+'.  
 1440--80's  
 1440--'80s  
 1440---'80s