Accept valid Accept headers in swob.

"Accept: application/xml; charset=UTF-8" is totally valid, and has an
implicit q (quality) value of 1.0, just the same as "Accept: text/xml"
does.

Also, you can say things like:
Accept: text/xml; charset=UTF-8; q=0.9; anglebrackets="are awesome"
with as many arbitrary extensions as you want.

See RFC 2616 sections 14.1 Accept and 2.2 Basic Rules for details.

Fixes bug 1202453.

Change-Id: I18e6d0ee3fd6f9d889275ee8335e711c729b7171

swift/common/swob.py

@@ -603,9 +603,17 @@ class Accept(object):
 
     :param headerval: value of the header as a str
     """
-    token = r'[^()<>@,;:\"/\[\]?={}\x00-\x20\x7f]+'  # RFC 2616 2.2
-    acc_pattern = re.compile(r'^\s*(' + token + r')/(' + token +
-                             r')(;\s*q=([\d.]+))?\s*$')
+
+    # RFC 2616 section 2.2
+    token = r'[^()<>@,;:\"/\[\]?={}\x00-\x20\x7f]+'
+    qdtext = r'[^"]'
+    quoted_pair = r'(?:\\.)'
+    quoted_string = r'"(?:' + qdtext + r'|' + quoted_pair + r')*"'
+    extension = (r'(?:\s*;\s*(?:' + token + r")\s*=\s*" + r'(?:' + token +
+                 r'|' + quoted_string + r'))')
+    acc = (r'^\s*(' + token + r')/(' + token +
+           r')(' + extension + r'*?\s*)$')
+    acc_pattern = re.compile(acc)
 
     def __init__(self, headerval):
         self.headerval = headerval
@@ -618,8 +626,22 @@ class Accept(object):
             type_parms = self.acc_pattern.findall(typ)
             if not type_parms:
                 raise ValueError('Invalid accept header')
-            typ, subtype, parms, quality = type_parms[0]
-            quality = float(quality or '1.0')
+            typ, subtype, parms = type_parms[0]
+            parms = [p.strip() for p in parms.split(';') if p.strip()]
+
+            seen_q_already = False
+            quality = 1.0
+
+            for parm in parms:
+                name, value = parm.split('=')
+                name = name.strip()
+                value = value.strip()
+                if name == 'q':
+                    if seen_q_already:
+                        raise ValueError('Multiple "q" params')
+                    seen_q_already = True
+                    quality = float(value)
+
             pattern = '^' + \
                 (self.token if typ == '*' else re.escape(typ)) + '/' + \
                 (self.token if subtype == '*' else re.escape(subtype)) + '$'

test/unit/common/test_swob.py

@@ -261,7 +261,10 @@ class TestAccept(unittest.TestCase):
 
     def test_accept_xml(self):
         for accept in ('application/xml', 'application/xml;q=1.0,*/*;q=0.9',
-                       '*/*;q=0.9,application/xml;q=1.0'):
+                       '*/*;q=0.9,application/xml;q=1.0',
+                       'application/xml;charset=UTF-8',
+                       'application/xml;charset=UTF-8;qws="quoted with space"',
+                       'application/xml; q=0.99 ; qws="quoted with space"'):
             acc = swift.common.swob.Accept(accept)
             match = acc.best_match(['text/plain', 'application/xml',
                                    'text/xml'])
@@ -270,7 +273,10 @@ class TestAccept(unittest.TestCase):
     def test_accept_invalid(self):
         for accept in ('*', 'text/plain,,', 'some stuff',
                        'application/xml;q=1.0;q=1.1', 'text/plain,*',
-                       'text /plain', 'text\x7f/plain'):
+                       'text /plain', 'text\x7f/plain',
+                       'text/plain;a=b=c',
+                       'text/plain;q=1;q=2',
+                       'text/plain; ubq="unbalanced " quotes"'):
             acc = swift.common.swob.Accept(accept)
             match = acc.best_match(['text/plain', 'application/xml',
                                    'text/xml'])
@@ -280,6 +286,7 @@ class TestAccept(unittest.TestCase):
         acc = swift.common.swob.Accept("application/json")
         self.assertEquals(repr(acc), "application/json")
 
+
 class TestRequest(unittest.TestCase):
     def test_blank(self):
         req = swift.common.swob.Request.blank(