Attempt to mock a werkzeug server with range requests

Please see the CI logs since I'm not exactly sure how to interpret it.

Author: McSinyx

tests/lib/server.py

@@ -7,6 +7,7 @@
 
 from mock import Mock
 from pip._vendor.contextlib2 import nullcontext
+from werkzeug.http import parse_range_header
 from werkzeug.serving import WSGIRequestHandler
 from werkzeug.serving import make_server as _make_server
 
@@ -217,6 +218,40 @@ def responder(environ, start_response):
     return responder
 
 
+def file_range_response(path):
+    # type: (str) -> Responder
+    def responder(environ, start_response):
+        # type: (Environ, StartResponse) -> Body
+        size = os.stat(path).st_size
+        if 'Range' not in environ:
+            start_response(
+                "200 OK", [
+                    ("Accept-Ranges", "bytes"),
+                    ("Content-Length", str(size)),
+                    ("Content-Type", "application/octet-stream"),
+                ],
+            )
+            if environ['REQUEST_METHOD'] == 'HEAD':
+                return []
+            with open(path, 'rb') as f:
+                return [f.read()]
+
+        # TODO: Multipart ranges
+        start, end = parse_range_header(environ['Range']).ranges[0]
+        length = end - start + 1
+        start_response(
+            "206 Partial Content", [
+                ("Content-Length", str(length)),
+                ("Content-Range", "{}-{}/{}".format(start, end, size)),
+                ("Content-Type", "application/octet-stream"),
+            ],
+        )
+        with open(path, 'rb') as f:
+            f.seek(start)
+            return [f.read(length)]
+    return responder
+
+
 def authorization_response(path):
     def responder(environ, start_response):
         # type: (Environ, StartResponse) -> Body

tests/unit/test_network_lazy_wheel.py

@@ -8,7 +8,7 @@
     dist_from_wheel_url,
 )
 from pip._internal.network.session import PipSession
-from tests.lib.server import file_response
+from tests.lib.server import file_range_response, file_response
 
 MYPY_0_782_WHL = (
     'https://files.pythonhosted.org/packages/9d/65/'
@@ -28,6 +28,16 @@ def session():
     return PipSession()
 
 
+@fixture
+def mypy_whl_range(mock_server, shared_data):
+    mypy_whl = shared_data.packages / 'mypy-0.782-py3-none-any.whl'
+    mock_server.set_responses([file_range_response(mypy_whl)])
+    mock_server.start()
+    base_address = 'http://{}:{}'.format(mock_server.host, mock_server.port)
+    yield "{}/{}".format(base_address, 'mypy-0.782-py3-none-any.whl')
+    mock_server.stop()
+
+
 @fixture
 def mypy_whl_no_range(mock_server, shared_data):
     mypy_whl = shared_data.packages / 'mypy-0.782-py3-none-any.whl'
@@ -39,9 +49,9 @@ def mypy_whl_no_range(mock_server, shared_data):
 
 
 @mark.network
-def test_dist_from_wheel_url(session):
+def test_dist_from_wheel_url(session, mypy_whl_range):
     """Test if the acquired distribution contain correct information."""
-    dist = dist_from_wheel_url('mypy', MYPY_0_782_WHL, session)
+    dist = dist_from_wheel_url('mypy', mypy_whl_range, session)
     assert dist.key == 'mypy'
     assert dist.version == '0.782'
     assert dist.extras == ['dmypy']