Adjusted quoting to DOT lang specification

There was some differences between how pydot quotes IDs (names, attrs)
and how it is defined in DOT language specification (and how pygraphviz
does it).
New test with covered cases has been added and new regexpes
for checking IDs has been also added.
Fixes #36

Author: prmtl

pydot_ng/__init__.py

@@ -198,15 +198,13 @@ def __repr__(self):
         return "frozendict(%s)" % dict.__repr__(self)
 
 
-dot_keywords = ['graph', 'subgraph', 'digraph', 'node', 'edge', 'strict']
-
-id_re_alpha_nums = re.compile('^[_a-zA-Z][a-zA-Z0-9_,]*$', re.UNICODE)
-id_re_alpha_nums_with_ports = re.compile(
-    '^[_a-zA-Z][a-zA-Z0-9_,:\"]*[a-zA-Z0-9_,\"]+$', re.UNICODE)
-id_re_num = re.compile('^[0-9,]+$', re.UNICODE)
-id_re_with_port = re.compile('^([^:]*):([^:]*)$', re.UNICODE)
-id_re_dbl_quoted = re.compile('^\".*\"$', re.S | re.UNICODE)
-id_re_html = re.compile('^<.*>$', re.S | re.UNICODE)
+# cases when no qoutes needed, from http://www.graphviz.org/doc/info/lang.html
+dot_keywords = ('graph', 'subgraph', 'digraph', 'node', 'edge', 'strict')
+id_alpha_num = re.compile(r'^[_a-zA-Z\200-\377][_a-zA-Z0-9\200-\377]*$',
+                          re.UNICODE)
+id_num = re.compile(r'^[-]?(\.[0-9]+|[0-9]+(\.[0-9]*)?)$', re.UNICODE)
+id_html = re.compile(r'^<.*>$', re.DOTALL | re.UNICODE)
+id_quoted = re.compile(r'^".*"$', re.DOTALL | re.UNICODE)
 
 
 def needs_quotes(s):
@@ -228,19 +226,18 @@ def needs_quotes(s):
     if s in dot_keywords:
         return False
 
-    chars = [ord(c) for c in s if ord(c) > 0x7f or ord(c) == 0]
-    if chars and not id_re_dbl_quoted.match(s) and not id_re_html.match(s):
-        return True
-
     for test_re in [
-            id_re_alpha_nums, id_re_num, id_re_dbl_quoted,
-            id_re_html, id_re_alpha_nums_with_ports]:
+        id_alpha_num,
+        id_num,
+        id_html,
+        id_quoted,
+    ]:
         if test_re.match(s):
             return False
 
-    m = id_re_with_port.match(s)
-    if m:
-        return needs_quotes(m.group(1)) or needs_quotes(m.group(2))
+    chars = [ord(c) for c in s if ord(c) > 0x7f or ord(c) == 0]
+    if chars and not id_quoted.match(s) and not id_html.match(s):
+        return True
 
     return True
 

test/test_pydot.py

@@ -285,6 +285,31 @@ def test_quoting(self):
         data = g.create(format='jpe')
         self.assertEqual(len(data) > 0, True)
 
+
+class TestQuoting(unittest.TestCase):
+
+    def test_quote_cases(self):
+        checks = (
+            ('A:', '"A:"'),
+            (':B', '":B"'),
+            ('A:B', '"A:B"'),
+            ('1A', '"1A"'),
+            ('A', 'A'),
+            ('11', '11'),
+            ('_xyz', '_xyz'),
+            ('.11', '.11'),
+            ('-.09', '-.09'),
+            ('1.8', '1.8'),
+            ('', '""'),
+            ('"1abc"', '"1abc"'),
+            ('@', '"@"'),
+            ('ÿ', 'ÿ'),
+        )
+
+        for input, expected in checks:
+            self.assertEqual(pydot.quote_if_necessary(input), expected)
+
+
 if __name__ == '__main__':
     suite = unittest.TestLoader().loadTestsFromTestCase(TestGraphAPI)
     unittest.TextTestRunner(verbosity=2).run(suite)