Don't omit Content-Length header for Content-Length: 0 cases

starlette/responses.py

@@ -70,8 +70,8 @@ def init_headers(self, headers: typing.Mapping[str, str] = None) -> None:
             populate_content_length = b"content-length" not in keys
             populate_content_type = b"content-type" not in keys
 
-        body = getattr(self, "body", b"")
-        if body and populate_content_length:
+        if populate_content_length:
+            body = getattr(self, "body", b"")
             content_length = str(len(body))
             raw_headers.append((b"content-length", content_length.encode("latin-1")))
 
@@ -289,7 +289,7 @@ def set_stat_headers(self, stat_result: os.stat_result) -> None:
         etag_base = str(stat_result.st_mtime) + "-" + str(stat_result.st_size)
         etag = md5_hexdigest(etag_base.encode(), usedforsecurity=False)
 
-        self.headers.setdefault("content-length", content_length)
+        self.headers["content-length"] = content_length
         self.headers.setdefault("last-modified", last_modified)
         self.headers.setdefault("etag", etag)
 

starlette/staticfiles.py

@@ -100,7 +100,7 @@ async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
     def get_path(self, scope: Scope) -> str:
         """
         Given the ASGI scope, return the `path` string to serve up,
-        with OS specific path seperators, and any '..', '.' components removed.
+        with OS specific path separators, and any '..', '.' components removed.
         """
         return os.path.normpath(os.path.join(*scope["path"].split("/")))
 

tests/test_responses.py

@@ -13,6 +13,7 @@
     Response,
     StreamingResponse,
 )
+from starlette.testclient import TestClient
 
 
 def test_text_response(test_client_factory):
@@ -73,6 +74,20 @@ async def app(scope, receive, send):
     assert response.url == "http://testserver/I%20%E2%99%A5%20Starlette/"
 
 
+def test_redirect_response_content_length_header(test_client_factory):
+    async def app(scope, receive, send):
+        if scope["path"] == "/":
+            response = Response("hello", media_type="text/plain")  # pragma: nocover
+        else:
+            response = RedirectResponse("/")
+        await response(scope, receive, send)
+
+    client: TestClient = test_client_factory(app)
+    response = client.request("GET", "/redirect", allow_redirects=False)
+    assert response.url == "http://testserver/redirect"
+    assert response.headers["content-length"] == "0"
+
+
 def test_streaming_response(test_client_factory):
     filled_by_bg_task = ""
 
@@ -309,3 +324,8 @@ def test_head_method(test_client_factory):
     client = test_client_factory(app)
     response = client.head("/")
     assert response.text == ""
+
+
+def test_empty_response():
+    response = Response()
+    assert response.headers["Content-Length"] == "0"