Fix for #11, with chunked encoding, closing chunk is sometimes sent twice

eventlet/wsgi.py

@@ -270,7 +270,11 @@ class HttpProtocol(BaseHTTPServer.BaseHTTPRequestHandler):
 
             if use_chunked[0]:
                 ## Write the chunked encoding
-                towrite.append("%x\r\n%s\r\n" % (len(data), data))
+                if data:
+                    towrite.append("%x\r\n%s\r\n" % (len(data), data))
+                else:
+                    # last-chunk format
+                    towrite.append("0\r\n")
             else:
                 towrite.append(data)
             try:
@@ -315,16 +319,19 @@ class HttpProtocol(BaseHTTPServer.BaseHTTPRequestHandler):
                     headers_set[1].append(('Content-Length', str(sum(map(len, result)))))
                 towrite = []
                 towrite_size = 0
+                just_written_size = 0
                 for data in result:
                     towrite.append(data)
                     towrite_size += len(data)
                     if towrite_size >= self.minimum_chunk_size:
                         write(''.join(towrite))
                         towrite = []
+                        just_written_size = towrite_size
                         towrite_size = 0
                 if towrite:
+                    just_written_size = towrite_size
                     write(''.join(towrite))
-                if not headers_sent or use_chunked[0]:
+                if not headers_sent or (use_chunked[0] and just_written_size):
                     write('')
             except Exception, e:
                 self.close_connection = 1

tests/wsgi_test.py

@@ -328,7 +328,7 @@ class TestHttpd(LimitedTestCase):
         while chunklen:
             chunks += 1
             chunk = fd.read(chunklen)
-            fd.readline()
+            fd.readline()  # CRLF
             chunklen = int(fd.readline(), 16)
         self.assert_(chunks > 1)
 
@@ -768,5 +768,29 @@ class TestHttpd(LimitedTestCase):
                 pass # TODO: should test with OpenSSL
             greenthread.kill(g)
 
+    def test_zero_length_chunked_response(self):
+        def zero_chunked_app(env, start_response):
+            start_response('200 OK', [('Content-type', 'text/plain')])
+            yield ""
+
+        self.site.application = zero_chunked_app
+        sock = api.connect_tcp(
+            ('localhost', self.port))
+
+        fd = sock.makefile()
+        fd.write('GET / HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n')
+        fd.flush()
+        response = fd.read().split('\r\n')
+        headers = []
+        while True:
+            h = response.pop(0)
+            headers.append(h)
+            if h == '':
+                break
+        self.assert_('Transfer-Encoding: chunked' in ''.join(headers))
+        # should only be one chunk of zero size
+        self.assertEqual(response, ['0', ''])
+        
+
 if __name__ == '__main__':
     main()