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Hi,
in httplib.HTTPConnection._send_request (Python 2.6)
in httplib.HTTPConnection._set_content_length (Python 2.7)
and http.client.HTTPConnection._set_content_length (Python 3.3)
there are something like that :
 try:
 thelen = str(len(body))
 except TypeError as te:
 # If this is a file-like object, try to
 # fstat its file descriptor
 try:
 thelen = str(os.fstat(body.fileno()).st_size)
 except (AttributeError, OSError):
 # Don't send a length if this failed
 if self.debuglevel > 0: print("Cannot stat!!")
If I put StringIO object in body and I do :
>>> len(body)
AttributeError: StringIO instance has no attribute '__len__'
I haven't TypeError.
I think we need to replace :
 try:
 thelen = str(len(body))
 except TypeError as te:
by :
 if hasattr(body, "read"):
 ... # it's file-like object
 else:
 ... # it's string object
What do you think about ?

fileno and stat won't work on a StringIO object. So StringIO would need to be special cased to call getvalue.

> fileno and stat won't work on a StringIO object. So StringIO would need to be special cased to call getvalue.
Yes, but it isn't important in chunk transfer encoding.

But if the len information is available, why not return it?

> But if the len information is available, why not return it?
I use HTTPConnection to simulate Apple Finder WebDAV client.
When this WebDAV client do PUT request, it transmit data in chunked encoding mode and not set Content-Length HTTP field.
Do you understand my context ?
Regards,
Stephane

The code you are suggesting patching is trying its best to return a length. If that code needs to be fixed to not throw an error when confronted with a StringIO, then it should do its best to return a length. Your original message on the ticket did not mention chunked encoding, and indeed that appears to be correct. This bug doesn't appear, from what you have written and what I see in the 3.x code, to have anything to do with chunked encoding.

Hello Stephane,
> I use HTTPConnection to simulate Apple Finder WebDAV client. When
> this WebDAV client do PUT request, it transmit data in chunked
> encoding mode and not set Content-Length HTTP field.
> 
> Do you understand my context ?
Is the server at fault in not returning Content-Length?
Can you provide a full working snippet which demonstrates the bug you
are facing? I fear, if I am lacking some information to completely
determine what needs to be fixed (I understand the code change you
suggested, but also need to know why and under what practical
situation would code flow through that).

@harobed if you still have a problem please provide more data as requested in msg138692.

Length computation is being dealt with in issue 23350.

For the record, it looks like there were a few distinct but related problems here:
* Passing any StringIO object as the body is not supported (see <https://docs.python.org/2/library/httplib.html#httplib.HTTPConnection.request>), because no StringIO class implements the fileno() method.
* Passing a Python 2 natively implemented StringIO.StringIO instance triggers the same AttributeError exception as in Issue 15267, incompatibility with TemporaryFile objects.
* Even if HTTPConnection.request() did support calculating Content-Length for StringIO objects, it would still be wrong for chunk-encoded bodies. I think the lower-level endheaders() or send() methods should be used instead. Or see Issue 12319, about adding chunked encoding for request().