Fix empty file uploads

src/zope/publisher/browser.py

@@ -256,7 +256,7 @@ def _decode(self, text):
             envadapter = IUserPreferredCharsets(self)
             self.charsets = envadapter.getPreferredCharsets() or ['utf-8']
             self.charsets = [c for c in self.charsets if c != '*']
-        if not PYTHON2:
+        if not PYTHON2 and not isinstance(text, bytes):
             if self.charsets and self.charsets[0] == 'iso-8859-1':
                 # optimization: we are trying to decode something
                 # cgi.FieldStorage already decoded for us, let's just return it

src/zope/publisher/tests/test_browserrequest.py

@@ -41,6 +41,14 @@
 from zope.publisher.tests.basetestiapplicationrequest \
      import BaseTestIApplicationRequest
 
+
+EMPTY_FILE_BODY = b"""-----------------------------1
+Content-Disposition: form-data; name="upload"; filename=""
+Content-Type: application/octet-stream
+
+-----------------------------1--
+"""
+
 LARGE_FILE_BODY = b''.join([b"""-----------------------------1
 Content-Disposition: form-data; name="upload"; filename="test"
 Content-Type: text/plain
@@ -228,6 +236,15 @@ def testFileUploadPost(self):
         # Test that we can actually read the file data
         self.assertEqual(request.form['upload'].read(), b'Some data')
 
+    def testEmptyFilePost(self):
+        extra = {'REQUEST_METHOD':'POST',
+                 'PATH_INFO': u"/",
+                 'CONTENT_TYPE': 'multipart/form-data;\
+                 boundary=---------------------------1'}
+
+        request  = self._createRequest(extra, body=EMPTY_FILE_BODY)
+        request.processInputs()
+
     def testLargePostValue(self):
         extra = {'REQUEST_METHOD':'POST',
                  'PATH_INFO': u"/",