gh-105622: Parse HTTP headers with default email policy

Doc/library/http.client.rst

@@ -124,8 +124,9 @@ This module provides the following function:
 .. function:: parse_headers(fp)
 
    Parse the headers from a file pointer *fp* representing a HTTP
-   request/response. The file has to be a :class:`BufferedIOBase` reader
-   (i.e. not text) and must provide a valid :rfc:`2822` style header.
+   request/response according to the the default email policy
+   :data:`email.policy.default`. The file has to be a :class:`BufferedIOBase`
+   reader (i.e. not text) and must provide a valid :rfc:`2822` style header.
 
    This function returns an instance of :class:`http.client.HTTPMessage`
    that holds the header fields, but no payload

Lib/http/client.py

@@ -69,6 +69,7 @@
 """
 
 import email.parser
+import email.policy
 import email.message
 import errno
 import http
@@ -233,7 +234,8 @@ def _parse_header_lines(header_lines, _class=HTTPMessage):
 
     """
     hstring = b''.join(header_lines).decode('iso-8859-1')
-    return email.parser.Parser(_class=_class).parsestr(hstring)
+    return email.parser.Parser(_class=_class,
+                               policy=email.policy.default).parsestr(hstring)
 
 def parse_headers(fp, _class=HTTPMessage):
     """Parses only RFC2822 headers from a file pointer."""

Lib/test/test_docxmlrpc.py

@@ -93,7 +93,7 @@ def test_valid_get_response(self):
         response = self.client.getresponse()
 
         self.assertEqual(response.status, 200)
-        self.assertEqual(response.getheader("Content-type"), "text/html; charset=UTF-8")
+        self.assertEqual(response.getheader("Content-type"), "text/html; charset=\"UTF-8\"")
 
         # Server raises an exception if we don't start to read the data
         response.read()
@@ -103,7 +103,7 @@ def test_get_css(self):
         response = self.client.getresponse()
 
         self.assertEqual(response.status, 200)
-        self.assertEqual(response.getheader("Content-type"), "text/css; charset=UTF-8")
+        self.assertEqual(response.getheader("Content-type"), "text/css; charset=\"UTF-8\"")
 
         # Server raises an exception if we don't start to read the data
         response.read()

Lib/test/test_urllibnet.py

@@ -193,12 +193,10 @@ def test_header(self):
 
     def test_data_header(self):
         with self.urlretrieve(self.logo) as (file_location, fileheaders):
-            datevalue = fileheaders.get('Date')
-            dateformat = '%a, %d %b %Y %H:%M:%S GMT'
-            try:
-                time.strptime(datevalue, dateformat)
-            except ValueError:
-                self.fail('Date value not in %r format' % dateformat)
+            date = fileheaders.get('Date')
+            self.assertIsInstance(date, email.headerregistry.DateHeader,
+                                  "Date is not an instance of email.headerregistery.DateHeader")
+            self.assertIsNotNone(date.datetime, "Date is not in RFC 5322 format")
 
     def test_reporthook(self):
         records = []

Misc/NEWS.d/next/Library/2023-06-19-11-41-03.gh-issue-105622.UeKd3u.rst

@@ -0,0 +1,3 @@
+Update :func:`http.client.parse_headers` to use the default email policy
+:data:`email.policy.default` when parsing headers. Previously no email
+policy was specified which is not reccomended.