[Python-checkins] bpo-43972: Set content-length to 0 for http.server.SimpleHTTPRequestHandler 301s (GH-25705)

[orsenthil]

https://github.com/python/cpython/commit/fb427255614fc1f740e7785554c1da8ca39116c2
commit: fb427255614fc1f740e7785554c1da8ca39116c2
branch: main
author: Stephen Rosen <sirosen at globus.org>
committer: orsenthil <skumaran at gatech.edu>
date: 2021-05-06T12:25:52-07:00
summary:

bpo-43972: Set content-length to 0 for http.server.SimpleHTTPRequestHandler 301s (GH-25705)

* Set content-length for simple http server 301s

When http.server.SimpleHTTPRequestHandler sends a 301 (Moved
Permanently) due to a missing file, it does not set a Content-Length
of 0. Unfortunately, certain clients can be left waiting for the
connection to be closed in this circumstance, even though no body
will be sent. At time of writing, both curl and Firefox demonstrate
this behavior.

* Test Content-Length on simple http server redirect

When serving a redirect, the SimpleHTTPRequestHandler will now send
`Content-Length: 0`. Several tests for http.server already cover
various behaviors and checks including redirection. This change only
adds one check for the expected Content-Length on the simplest case
for a redirect.

* Add news entry for SimpleHTTPRequestHandler fix

* Clarify the specific kind of 301

Co-authored-by: Senthil Kumaran <skumaran at gatech.edu>

files:
A Misc/NEWS.d/next/Library/2021-04-30-16-58-24.bpo-43972.Y2r9lg.rst
M Lib/http/server.py
M Lib/test/test_httpservers.py

diff --git a/Lib/http/server.py b/Lib/http/server.py
index 94f730ed3445be..e985dfd5640086 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -689,6 +689,7 @@ def send_head(self):
                              parts[3], parts[4])
                 new_url = urllib.parse.urlunsplit(new_parts)
                 self.send_header("Location", new_url)
+                self.send_header("Content-Length", "0")
                 self.end_headers()
                 return None
             for index in "index.html", "index.htm":
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index 6b17817b22bf05..cb0a3aa9e40451 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -428,6 +428,7 @@ def test_get(self):
         self.check_status_and_reason(response, HTTPStatus.OK)
         response = self.request(self.base_url)
         self.check_status_and_reason(response, HTTPStatus.MOVED_PERMANENTLY)
+        self.assertEqual(response.getheader("Content-Length"), "0")
         response = self.request(self.base_url + '/?hi=2')
         self.check_status_and_reason(response, HTTPStatus.OK)
         response = self.request(self.base_url + '?hi=1')
diff --git a/Misc/NEWS.d/next/Library/2021-04-30-16-58-24.bpo-43972.Y2r9lg.rst b/Misc/NEWS.d/next/Library/2021-04-30-16-58-24.bpo-43972.Y2r9lg.rst
new file mode 100644
index 00000000000000..3d67b885bab105
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-04-30-16-58-24.bpo-43972.Y2r9lg.rst
@@ -0,0 +1,3 @@
+When :class:`http.server.SimpleHTTPRequestHandler` sends a
+``301 (Moved Permanently)`` for a directory path not ending with `/`, add a
+``Content-Length: 0`` header. This improves the behavior for certain clients.