Support single quotes too

README.rst

@@ -127,8 +127,10 @@ parenthesis. DjangoQL is case-sensitive.
 
 - model fields: exactly as they are defined in Python code. Access
   nested properties via ``.``, for example ``author.last_name``;
-- strings must be double-quoted. Single quotes are not supported.
-  To escape a double quote use ``\"``;
+- strings can be enclosed in either double quotes or single quotes.
+  To escape a quote, use ``\"`` for double quotes or ``\'`` for single quotes.
+  You can also use single quotes to enclose strings containing double quotes,
+  and vice versa;
 - boolean and null values: ``True``, ``False``, ``None``. Please note
   that they can be combined only with equality operators, so you can
   write ``published = False or date_published = None``, but

djangoql/lexer.py

@@ -53,9 +53,10 @@ def find_column(self, t):
 
     re_line_terminators = r'\n\r\u2028\u2029'
 
-    re_escaped_char = r'\\[\"\\/bfnrt]'
+    re_escaped_char = r'\\[\"\'/\\bfnrt]'
     re_escaped_unicode = r'\\u[0-9A-Fa-f]{4}'
-    re_string_char = r'[^\"\\' + re_line_terminators + u']'
+    re_string_char_double = r'[^\"\\' + re_line_terminators + u']'
+    re_string_char_single = r'[^\'\\' + re_line_terminators + u']'
 
     re_int_value = r'(-?0|-?[1-9][0-9]*)'
     re_fraction_part = r'\.[0-9]+'
@@ -106,7 +107,10 @@ def find_column(self, t):
 
     @TOKEN(r'\"(' + re_escaped_char +
            '|' + re_escaped_unicode +
-           '|' + re_string_char + r')*\"')
+           '|' + re_string_char_double + r')*\"|' +
+           r'\'(' + re_escaped_char +
+           '|' + re_escaped_unicode +
+           '|' + re_string_char_single + r')*\'')
     def t_STRING_VALUE(self, t):
         t.value = t.value[1:-1]  # cut leading and trailing quotes ""
         return t

test_project/core/tests/test_lexer.py

@@ -76,6 +76,33 @@ def test_string(self):
                 [('STRING_VALUE', s.strip('"'))],
             )
 
+    def test_string_single_quotes(self):
+        for s in ("''", u"''", "'42'", r"'\t\n\u0042 ^'"):
+            self.assert_output(
+                self.lexer.input(s),
+                [('STRING_VALUE', s.strip("'"))],
+            )
+
+    def test_string_mixed_quotes(self):
+        self.assert_output(
+            self.lexer.input("""'He said "hello"'"""),
+            [('STRING_VALUE', 'He said "hello"')],
+        )
+        self.assert_output(
+            self.lexer.input('''"It's working"'''),
+            [('STRING_VALUE', "It's working")],
+        )
+
+    def test_string_escaped_quotes(self):
+        self.assert_output(
+            self.lexer.input(r"'It\'s working'"),
+            [('STRING_VALUE', r"It\'s working")],
+        )
+        self.assert_output(
+            self.lexer.input(r'"He said \"hello\""'),
+            [('STRING_VALUE', r'He said \"hello\"')],
+        )
+
     def test_illegal_chars(self):
         for s in ('"', '^'):
             try:

test_project/core/tests/test_parser.py

@@ -79,6 +79,31 @@ def test_escaped_chars(self):
             self.parser.parse(u'options = "\\u041f \\u0438 \\u0429"'),
         )
 
+    def test_single_quoted_strings(self):
+        self.assertEqual(
+            Expression(Name('gender'), Comparison('='), Const('female')),
+            self.parser.parse("gender = 'female'"),
+        )
+        self.assertEqual(
+            Expression(Name('name'), Comparison('~'), Const('He said "hello"')),
+            self.parser.parse("""name ~ 'He said "hello"'"""),
+        )
+        self.assertEqual(
+            Expression(Name('name'), Comparison('~'), Const("It's working")),
+            self.parser.parse('''name ~ "It's working"'''),
+        )
+
+    def test_escaped_chars_single_quotes(self):
+        self.assertEqual(
+            Expression(Name('name'), Comparison('~'),
+                       Const(u"It's working")),
+            self.parser.parse(u"name ~ 'It\\'s working'"),
+        )
+        self.assertEqual(
+            Expression(Name('options'), Comparison('='), Const(u'П и Щ')),
+            self.parser.parse(u"options = '\\u041f \\u0438 \\u0429'"),
+        )
+
     def test_numbers(self):
         self.assertEqual(
             Expression(Name('pk'), Comparison('>'), Const(5)),