Support stream response

responder/models.py

@@ -1,4 +1,6 @@
+import functools
 import io
+import inspect
 import json
 import gzip
 from base64 import b64decode
@@ -13,7 +15,10 @@ from requests.structures import CaseInsensitiveDict
 from requests.cookies import RequestsCookieJar
 from starlette.datastructures import MutableHeaders
 from starlette.requests import Request as StarletteRequest
-from starlette.responses import Response as StarletteResponse
+from starlette.responses import (
+    Response as StarletteResponse,
+    StreamingResponse as StarletteStreamingResponse,
+)
 
 from urllib.parse import parse_qs
 
@@ -244,6 +249,7 @@ class Response:
         "formats",
         "cookies",
         "session",
+        "_stream",
     ]
 
     def __init__(self, req, *, formats):
@@ -255,6 +261,7 @@ class Response:
         self.media = (
             None
         )  #: A Python object that will be content-negotiated and sent back to the client. Typically, in JSON formatting.
+        self._stream = None
         self.headers = (
             {}
         )  #: A Python dictionary of ``{key: value}``, representing the headers of the response.
@@ -264,8 +271,19 @@ class Response:
             req.session.copy()
         )  #: The cookie-based session data, in dict form, to add to the Response.
 
+    # Property or func/dec
+    def stream(self, func, *args, **kwargs):
+        assert inspect.isasyncgenfunction(func)
+
+        self._stream = functools.partial(func, *args, **kwargs)
+
+        return func
+
     @property
     async def body(self):
+        if self._stream is not None:
+            return (self._stream(), {})
+
         if self.content is not None:
             return (self.content, {})
 
@@ -287,7 +305,11 @@ class Response:
         if self.headers:
             headers.update(self.headers)
 
-        response = StarletteResponse(
-            body, status_code=self.status_code, headers=headers
-        )
+        if self._stream is not None:
+            response_cls = StarletteStreamingResponse
+        else:
+            response_cls = StarletteResponse
+
+        response = response_cls(body, status_code=self.status_code, headers=headers)
+
         await response(receive, send)

tests/test_responder.py

@@ -680,3 +680,41 @@ def test_staticfiles_custom_route(tmpdir):
     # Not found on dir listing
     r = session.get(f"{static_route}")
     assert r.status_code == api.status_codes.HTTP_404
+
+
+def test_stream(api, session):
+    async def shout_stream(who):
+        for c in who.upper():
+            yield c
+
+    @api.route("/{who}")
+    async def greeting(req, resp, *, who):
+
+        resp.stream(shout_stream, who)
+
+    r = session.get("/morocco")
+    assert r.text == "MOROCCO"
+
+    @api.route("/")
+    async def home(req, resp):
+        # Raise when it's not an async generator
+        with pytest.raises(AssertionError):
+
+            def foo():
+                pass
+
+            res.stream(foo)
+
+        with pytest.raises(AssertionError):
+
+            async def foo():
+                pass
+
+            res.stream(foo)
+
+        with pytest.raises(AssertionError):
+
+            def foo():
+                yield "oopsie"
+
+            res.stream(foo)