support 'rb' string prefix in addition to 'br' (Py3 allows it)

Cython/Compiler/Lexicon.py

@@ -4,7 +4,10 @@
 #
 
 raw_prefixes = "rR"
-string_prefixes = "cCuUbB"
+bytes_prefixes = "bB"
+string_prefixes = "uU" + bytes_prefixes
+char_prefixes = "cC"
+any_string_prefix = raw_prefixes + string_prefixes + char_prefixes
 IDENT = 'IDENT'
 
 def make_lexicon():
@@ -60,7 +63,10 @@ def make_lexicon():
         + Str('"""')
     )
 
-    beginstring = Opt(Any(string_prefixes)) + Opt(Any(raw_prefixes)) + (Str("'") | Str('"') | Str("'''") | Str('"""'))
+    beginstring = Opt(Any(string_prefixes) + Opt(Any(raw_prefixes)) |
+                      Any(raw_prefixes) + Opt(Any(bytes_prefixes)) |
+                      Any(char_prefixes)
+                      ) + (Str("'") | Str('"') | Str("'''") | Str('"""'))
     two_oct = octdigit + octdigit
     three_oct = octdigit + octdigit + octdigit
     two_hex = hexdigit + hexdigit

Cython/Compiler/Parsing.py

@@ -785,13 +785,17 @@ def p_string_literal(s, kind_override=None):
 
     # s.sy == 'BEGIN_STRING'
     pos = s.position()
-    is_raw = 0
+    is_raw = False
     is_python3_source = s.context.language_level >= 3
     has_non_ASCII_literal_characters = False
     kind = s.systring[:1].lower()
     if kind == 'r':
-        kind = ''
-        is_raw = 1
+        # Py3 allows both 'br' and 'rb' as prefix
+        if s.systring[1:2].lower() == 'b':
+            kind = 'b'
+        else:
+            kind = ''
+        is_raw = True
     elif kind in 'ub':
         is_raw = s.systring[1:2].lower() == 'r'
     elif kind != 'c':
@@ -808,6 +812,7 @@ def p_string_literal(s, kind_override=None):
             chars = StringEncoding.StrLiteralBuilder(s.source_encoding)
         else:
             chars = StringEncoding.BytesLiteralBuilder(s.source_encoding)
+
     while 1:
         s.next()
         sy = s.sy
@@ -872,6 +877,7 @@ def p_string_literal(s, kind_override=None):
         else:
             s.error("Unexpected token %r:%r in string literal" %
                     (sy, s.systring))
+
     if kind == 'c':
         unicode_value = None
         bytes_value = chars.getchar()

Cython/Compiler/Scanning.py

@@ -7,14 +7,14 @@ import os
 import platform
 
 import cython
-cython.declare(EncodedString=object, string_prefixes=object, raw_prefixes=object, IDENT=unicode,
+cython.declare(EncodedString=object, any_string_prefix=unicode, IDENT=unicode,
                print_function=object)
 
 from Cython import Utils
 from Cython.Plex.Scanners import Scanner
 from Cython.Plex.Errors import UnrecognizedInput
 from Errors import error
-from Lexicon import string_prefixes, raw_prefixes, make_lexicon, IDENT
+from Lexicon import any_string_prefix, make_lexicon, IDENT
 from Future import print_function
 
 from StringEncoding import EncodedString
@@ -340,9 +340,7 @@ class PyrexScanner(Scanner):
     }
 
     def begin_string_action(self, text):
-        if text[:1] in string_prefixes:
-            text = text[1:]
-        if text[:1] in raw_prefixes:
+        while text[:1] in any_string_prefix:
             text = text[1:]
         self.begin(self.string_states[text])
         self.produce('BEGIN_STRING')

tests/run/strliterals.pyx

@@ -180,6 +180,17 @@ s7 = Br"abc\x11"
 s8 = bR"abc\x11"
 s9 = BR"abc\x11"
 
+# and in reversed order: r+b
+s6_2 = rb"abc\x11"
+s7_2 = rB"abc\x11"
+s8_2 = Rb"abc\x11"
+s9_2 = RB"abc\x11"
+
+assert s6 == s6_2
+assert s7 == s7_2
+assert s8 == s8_2
+assert s9 == s9_2
+
 u1 = u"abc\x11"
 u2 = U"abc\x11"
 u3 = ur"abc\x11"