gh-135056: Support multiple headers of the same name.

Author: aisipos

Doc/library/http.server.rst

@@ -375,8 +375,8 @@ instantiation, of which this module provides three different variants:
       The *directory* parameter accepts a :term:`path-like object`.
 
    .. versionchanged:: next
-      Added *response_headers*, which accepts an optional dictionary of
-      additional HTTP headers to add to each successful HTTP status 200
+      Added *response_headers*, which accepts an optional iterable of
+      name/value pairs of HTTP headers to add to each successful HTTP status 200
       response. All other status code responses will not include these headers.
 
    A lot of the work, such as parsing the request, is done by the base class
@@ -433,8 +433,8 @@ instantiation, of which this module provides three different variants:
       followed by a ``'Content-Length:'`` header with the file's size and a
       ``'Last-Modified:'`` header with the file's modification time.
 
-      The headers specified in the dictionary instance argument
-      ``response_headers`` are each individually sent in the response.
+      The instance attribute ``response_headers`` is used as an iterable of
+      name/value pairs to set user specified custom response headers.
 
       Then follows a blank line signifying the end of the headers, and then the
       contents of the file are output.

Lib/http/server.py

@@ -718,7 +718,7 @@ def send_custom_response_headers(self):
         """Send the headers stored in self.response_headers"""
         # User specified response_headers
         if self.response_headers is not None:
-            for header, value in self.response_headers.items():
+            for header, value in self.response_headers:
                 self.send_header(header, value)
 
     def send_head(self):
@@ -1056,9 +1056,9 @@ def _main(args=None):
         except OSError as e:
             parser.error(f"Failed to read TLS password file: {e}")
 
-    response_headers = {}
+    response_headers = []
     for header, value in args.header or []:
-        response_headers[header] = value
+        response_headers.append((header, value))
 
     # ensure dual-stack is not disabled; ref #38907
     class DualStackServerMixin:

Lib/test/test_httpservers.py

@@ -830,25 +830,27 @@ def test_path_without_leading_slash(self):
                          self.tempdir_name + "/?hi=1")
 
     def test_custom_headers_list_dir(self):
-        with mock.patch.object(self.request_handler, 'custom_headers', new={
-            'X-Test1': 'test1',
-            'X-Test2': 'test2',
-        }):
+        with mock.patch.object(self.request_handler, 'custom_headers', new=[
+            ('X-Test1', 'test1'),
+            ('X-Test2', 'test2'),
+        ]):
             response = self.request(self.base_url + '/')
             self.assertEqual(response.getheader("X-Test1"), 'test1')
             self.assertEqual(response.getheader("X-Test2"), 'test2')
 
     def test_custom_headers_get_file(self):
-        with mock.patch.object(self.request_handler, 'custom_headers', new={
-            'X-Test1': 'test1',
-            'X-Test2': 'test2',
-        }):
+        with mock.patch.object(self.request_handler, 'custom_headers', new=[
+            ('Set-Cookie', 'test1=value1'),
+            ('Set-Cookie', 'test2=value2'),
+            ('X-Test1', 'value3'),
+        ]):
             data = b"Dummy index file\r\n"
             with open(os.path.join(self.tempdir_name, 'index.html'), 'wb') as f:
                 f.write(data)
             response = self.request(self.base_url + '/')
-            self.assertEqual(response.getheader("X-Test1"), 'test1')
-            self.assertEqual(response.getheader("X-Test2"), 'test2')
+            self.assertEqual(response.getheader("Set-Cookie"),
+                                                'test1=value1, test2=value2')
+            self.assertEqual(response.getheader("X-Test1"), 'value3')
 
 class SocketlessRequestHandler(SimpleHTTPRequestHandler):
     def __init__(self, directory=None):
@@ -1498,7 +1500,7 @@ def test_response_headers_arg(self):
             HTTPServer, 'serve_forever'
         ) as mock_serve_forever:
             httpd = server._main(
-                ['-H', 'X-Test1', 'Test1', '-H', 'X-Test2', 'Test2', '8080']
+                ['-H', 'Set-Cookie', 'k=v', '-H', 'Set-Cookie', 'k2=v2', '8080']
             )
             request_handler_class = httpd.RequestHandlerClass
             with mock.patch.object(
@@ -1510,9 +1512,9 @@ def test_response_headers_arg(self):
                 httpd.finish_request(mock.Mock(), '127.0.0.1')
                 mock_handler_init.assert_called_once_with(
                     mock.ANY, mock.ANY, mock.ANY, directory=mock.ANY,
-                    response_headers={
-                        'X-Test1': 'Test1', 'X-Test2': 'Test2'
-                    }
+                    response_headers=[
+                        ('Set-Cookie', 'k=v'), ('Set-Cookie', 'k2=v2')
+                    ]
                 )