More consistent behavior regarding client disconnects.

docs/exceptions.rst

@@ -57,6 +57,8 @@ The following error classes exist in Werkzeug:
    This exception is used to signal unicode decode errors of request
    data.  For more information see the :ref:`unicode` chapter.
 
+.. autoexception:: ClientDisconnected
+
 
 Baseclass
 =========

werkzeug/exceptions.py

@@ -179,6 +179,21 @@ class BadRequest(HTTPException):
     )
 
 
+class ClientDisconnected(BadRequest):
+    """Internal exception that is raised if Werkzeug detects a disconnected
+    client.  Since the client is already gone at that point attempting to
+    send the error message to the client might not work and might ultimately
+    result in another exception in the server.  Mainly this is here so that
+    it is silenced by default as far as Werkzeug is concerned.
+
+    Since disconnections cannot be reliably detected and are unspecified
+    by WSGI to a large extend this might or might not be raised if a client
+    is gone.
+
+    .. versionadded:: 0.8
+    """
+
+
 class Unauthorized(HTTPException):
     """*401* `Unauthorized`
 

werkzeug/testsuite/wsgi.py

@@ -15,7 +15,7 @@
 from werkzeug.testsuite import WerkzeugTestCase
 
 from werkzeug.wrappers import BaseResponse
-from werkzeug.exceptions import BadRequest
+from werkzeug.exceptions import BadRequest, ClientDisconnected
 from werkzeug.test import Client, create_environ, run_wsgi_app
 from werkzeug import wsgi
 
@@ -140,6 +140,21 @@ def on_exhausted(self):
         stream = wsgi.LimitedStream(io, 3)
         assert stream.read(-1) == '123'
 
+    def test_limited_stream_disconnection(self):
+        io = StringIO('A bit of content')
+
+        # disconnect detection on out of bytes
+        stream = wsgi.LimitedStream(io, 255)
+        with self.assert_raises(ClientDisconnected):
+            stream.read()
+
+        # disconnect detection because file close
+        io = StringIO('x' * 255)
+        io.close()
+        stream = wsgi.LimitedStream(io, 255)
+        with self.assert_raises(ClientDisconnected):
+            stream.read()
+
     def test_path_info_extraction(self):
         x = wsgi.extract_path_info('http://example.com/app', '/app/hello')
         assert x == u'/hello'

werkzeug/wsgi.py

@@ -697,6 +697,15 @@ def on_exhausted(self):
         from werkzeug.exceptions import BadRequest
         raise BadRequest('input stream exhausted')
 
+    def on_disconnect(self):
+        """What should happen if a disconnect is detected?  The return
+        value of this function is returned from read functions in case
+        the client went away.  By default a
+        :exc:`~werkzeug.exceptions.ClientDisconnected` exception is raised.
+        """
+        from werkzeug.exceptions import ClientDisconnected
+        raise ClientDisconnected()
+
     def exhaust(self, chunk_size=1024 * 16):
         """Exhaust the stream.  This consumes all the data left until the
         limit is reached.
@@ -722,9 +731,12 @@ def read(self, size=None):
         if size is None or size == -1:  # -1 is for consistence with file
             size = self.limit
         to_read = min(self.limit - self._pos, size)
-        read = self._read(to_read)
+        try:
+            read = self._read(to_read)
+        except (IOError, ValueError):
+            return self.on_disconnect()
         if to_read and len(read) != to_read:
-            raise IOError('Stream has gone away')
+            return self.on_disconnect()
         self._pos += len(read)
         return read
 
@@ -736,9 +748,12 @@ def readline(self, size=None):
             size = self.limit - self._pos
         else:
             size = min(size, self.limit - self._pos)
-        line = self._readline(size)
+        try:
+            line = self._readline(size)
+        except (ValueError, IOError):
+            return self.on_disconnect()
         if size and not line:
-            raise IOError('Stream has gone away')
+            return self.on_disconnect()
         self._pos += len(line)
         return line