Add utils for validating and splitting quotes

Now Murano and Glance have similiar implementations of validating
and splitting quotes for using operator 'in' in their API [1],[2].

The style of this functionality should be common as they follow
appropriate api-wg style [3]. So it would be great to have them
implemented in one place and reuse in different projects.

TBD: add appropriate commits to Murano and Glance if this patch
isn't revoked.

[1]: https://github.com/openstack/glance/blob/master/glance/common/utils.py#L601-L644
[2]: https://github.com/openstack/murano/blob/master/murano/common/utils.py#L250-L301
[3]: https://specs.openstack.org/openstack/api-wg/guidelines/pagination_filter_sort.html#filtering

Change-Id: I15236d28b2136153db093590fb4dae65a87eb3e3
Co-Authored-By: Alexis Lee <lxsli@hpe.com>

oslo_utils/strutils.py

@@ -22,6 +22,7 @@ import math
 import re
 import unicodedata
 
+import pyparsing as pp
 import six
 from six.moves import urllib
 
@@ -468,3 +469,20 @@ def split_path(path, minsegs=1, maxsegs=None, rest_with_last=False):
     segs = segs[1:maxsegs]
     segs.extend([None] * (maxsegs - 1 - len(segs)))
     return segs
+
+
+def split_by_commas(value):
+    """Split values by commas and quotes according to api-wg
+
+    :param value: value to be split
+
+    .. versionadded:: 3.17
+    """
+    word = (pp.QuotedString(quoteChar='"', escChar='\\')
+            | pp.Word(pp.printables, excludeChars='",'))
+    grammar = pp.stringStart + pp.delimitedList(word) + pp.stringEnd
+
+    try:
+        return list(grammar.parseString(value))
+    except pp.ParseException:
+        raise ValueError("Invalid value: %s" % value)

oslo_utils/tests/test_strutils.py

@@ -762,3 +762,30 @@ class SplitPathTestCase(test_base.BaseTestCase):
             strutils.split_path('o\nn e', 2, 3, True)
         except ValueError as err:
             self.assertEqual(str(err), 'Invalid path: o%0An%20e')
+
+
+class SplitByCommas(test_base.BaseTestCase):
+    def test_not_closed_quotes(self):
+        self.assertRaises(ValueError, strutils.split_by_commas, '"ab","b""')
+
+    def test_no_comma_before_opening_quotes(self):
+        self.assertRaises(ValueError, strutils.split_by_commas, '"ab""b"')
+
+    def test_quote_inside_unquoted(self):
+        self.assertRaises(ValueError, strutils.split_by_commas, 'a"b,cd')
+
+    def check(self, expect, input):
+        self.assertEqual(expect, strutils.split_by_commas(input))
+
+    def test_plain(self):
+        self.check(["a,b", "ac"], '"a,b",ac')
+
+    def test_with_backslash_inside_quoted(self):
+        self.check(['abc"', 'de', 'fg,h', 'klm\\', '"nop'],
+                   r'"abc\"","de","fg,h","klm\\","\"nop"')
+
+    def test_with_backslash_inside_unquoted(self):
+        self.check([r'a\bc', 'de'], r'a\bc,de')
+
+    def test_with_escaped_quotes_in_row_inside_quoted(self):
+        self.check(['a"b""c', 'd'], r'"a\"b\"\"c",d')