Add env-var to force binary content-type for files

Fixes EpicWink#9

Author: EpicWink

README.md

@@ -70,6 +70,9 @@ change in a package index.
   Disable files-cache by setting this to 0
 * `PROXPI_CACHE_DIR`: downloaded project files cache directory path, default: a new
   temporary directory
+* `PROXPI_BINARY_FILE_MIME_TYPE=1`: force file-response content-type to
+  `"application/octet-stream"` instead of letting Flask guess it. This may be needed
+  if your package installer (eg Poetry) mishandles responses with declared encoding.
 
 ### Considerations with CI
 `proxpi` was designed with three goals (particularly for continuous integration (CI)):

src/proxpi/server.py

@@ -65,6 +65,11 @@ def _set_handler(self, *_, **__):
             handler.level = logging.DEBUG
 logger.info("Cache: %r", cache)
 
+BINARY_FILE_MIME_TYPE = (
+    os.environ.get("PROXPI_BINARY_FILE_MIME_TYPE", "")
+).lower() not in ("", "0", "no", "off", "false")
+_file_mime_type = "application/octet-stream" if BINARY_FILE_MIME_TYPE else None
+
 
 def _compress(response: t.Union[str, flask.Response]) -> flask.Response:
     response = flask.make_response(response)
@@ -123,7 +128,7 @@ def get_file(package_name: str, file_name: str):
     scheme = urllib.parse.urlparse(path).scheme
     if scheme and scheme != "file":
         return flask.redirect(path)
-    return flask.send_file(path)
+    return flask.send_file(path, mimetype=_file_mime_type)
 
 
 @app.route("/cache/list", methods=["DELETE"])

tests/test_integration.py

@@ -238,3 +238,25 @@ def test_download_file_failed(server, tmp_path):
     url_parsed = urllib_parse.urlsplit(response.headers["location"])
     assert url_parsed.netloc == "files.pythonhosted.org"
     assert posixpath.split(url_parsed.path)[1] == "Jinja2-2.11.1-py2.py3-none-any.whl"
+
+
+@pytest.mark.parametrize("file_mime_type", ["application/octet-stream", None])
+def test_download_file_representation(server, tmp_path, file_mime_type):
+    """Test package file content type and encoding."""
+    (tmp_path / "packages").mkdir()
+    file_mime_type_patch = mock.patch.object(
+        proxpi_server, "_file_mime_type", file_mime_type
+    )
+    with file_mime_type_patch:
+        response = requests.get(
+            "http://127.0.0.1:5042/index/proxpi/proxpi-1.0.0.tar.gz",
+            allow_redirects=False,
+        )
+    assert response.status_code == 200
+    if file_mime_type:
+        assert response.headers["Content-Type"] == "application/octet-stream"
+        assert not response.headers.get("Content-Encoding")
+    else:
+        assert response.headers["Content-Type"] == "application/x-tar"
+        assert response.headers["Content-Encoding"] == "gzip"
+    response.close()