Issue #8478: Untokenizer.compat now processes first token from iterator input.

Patch based on lines from Georg Brandl, Eric Snow, and Gareth Rees.

Lib/test/test_tokenize.py

@@ -627,9 +627,17 @@ class UntokenizeTest(TestCase):
                 'start (1,3) precedes previous end (2,2)')
         self.assertRaises(ValueError, u.add_whitespace, (2,1))
 
-__test__ = {"doctests" : doctests, 'decistmt': decistmt}
+    def test_iter_compat(self):
+        u = Untokenizer()
+        token = (NAME, 'Hello')
+        u.compat(token, iter([]))
+        self.assertEqual(u.tokens, ["Hello "])
+        u = Untokenizer()
+        self.assertEqual(u.untokenize(iter([token])), 'Hello ')
 
 
+__test__ = {"doctests" : doctests, 'decistmt': decistmt}
+
 def test_main():
     from test import test_tokenize
     test_support.run_doctest(test_tokenize, True)

Lib/tokenize.py

@@ -26,6 +26,7 @@ __author__ = 'Ka-Ping Yee <ping@lfw.org>'
 __credits__ = ('GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, '
                'Skip Montanaro, Raymond Hettinger')
 
+from itertools import chain
 import string, re
 from token import *
 
@@ -192,9 +193,10 @@ class Untokenizer:
             self.tokens.append(" " * col_offset)
 
     def untokenize(self, iterable):
-        for t in iterable:
+        it = iter(iterable)
+        for t in it:
             if len(t) == 2:
-                self.compat(t, iterable)
+                self.compat(t, it)
                 break
             tok_type, token, start, end, line = t
             self.add_whitespace(start)
@@ -206,16 +208,12 @@ class Untokenizer:
         return "".join(self.tokens)
 
     def compat(self, token, iterable):
-        startline = False
         indents = []
         toks_append = self.tokens.append
-        toknum, tokval = token
-        if toknum in (NAME, NUMBER):
-            tokval += ' '
-        if toknum in (NEWLINE, NL):
-            startline = True
+        startline = token[0] in (NEWLINE, NL)
         prevstring = False
-        for tok in iterable:
+        
+        for tok in chain([token], iterable):
             toknum, tokval = tok[:2]
 
             if toknum in (NAME, NUMBER):

Misc/NEWS

@@ -42,6 +42,9 @@ Library
 - Issue #17671: Fixed a crash when use non-initialized io.BufferedRWPair.
   Based on patch by Stephen Tu.
 
+- Issue #8478: Untokenizer.compat processes first token from iterator input.
+  Patch based on lines from Georg Brandl, Eric Snow, and Gareth Rees.  
+
 - Issue #20594: Avoid name clash with the libc function posix_close.
 
 - Issue #19856: shutil.move() failed to move a directory to other directory