From 8332a8067a6b7226c3192192f801a3dce34711cd Mon Sep 17 00:00:00 2001
From: Erik Aker <eraker@gmail.com>
Date: Tue, 28 Apr 2020 08:29:54 -0700
Subject: [PATCH] First pass adding next qparam to redirect

---
 docs/authentication.md       | 23 +++++++++++++++++++++++
 starlette/authentication.py  | 15 +++++++++++++--
 tests/test_authentication.py | 11 +++++++++--
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/docs/authentication.md b/docs/authentication.md
index d5970aa4f..8c2a895a6 100644
--- a/docs/authentication.md
+++ b/docs/authentication.md
@@ -131,6 +131,29 @@ async def dashboard(request):
     ...
 ```
 
+When redirecting users, the page you redirect them to will include URL they originally requested at the `next` query param:
+
+```python
+from starlette.authentication import requires
+from starlette.responses import RedirectResponse
+
+
+@requires('authenticated', redirect='login')
+async def admin(request):
+    ...
+
+
+async def login(request):
+    if request.method == "POST":
+        # Now that the user is authenticated,
+        # we can send them to their original request destination
+        if request.user.is_authenticated:
+            next_url = request.query_params.get("next")
+            if next_url:
+                return RedirectResponse(next_url)
+            return RedirectResponse("/")
+```
+
 For class-based endpoints, you should wrap the decorator
 around a method on the class.
 
diff --git a/starlette/authentication.py b/starlette/authentication.py
index 1fc6acaeb..92064b23b 100644
--- a/starlette/authentication.py
+++ b/starlette/authentication.py
@@ -2,6 +2,7 @@
 import functools
 import inspect
 import typing
+from urllib.parse import urlencode
 
 from starlette.exceptions import HTTPException
 from starlette.requests import HTTPConnection, Request
@@ -62,7 +63,12 @@ async def async_wrapper(
 
                 if not has_required_scope(request, scopes_list):
                     if redirect is not None:
-                        return RedirectResponse(url=request.url_for(redirect))
+                        orig_request_qparam = urlencode({"next": str(request.url)})
+                        next_url = "{redirect_path}?{orig_request}".format(
+                            redirect_path=request.url_for(redirect),
+                            orig_request=orig_request_qparam,
+                        )
+                        return RedirectResponse(url=next_url)
                     raise HTTPException(status_code=status_code)
                 return await func(*args, **kwargs)
 
@@ -77,7 +83,12 @@ def sync_wrapper(*args: typing.Any, **kwargs: typing.Any) -> Response:
 
                 if not has_required_scope(request, scopes_list):
                     if redirect is not None:
-                        return RedirectResponse(url=request.url_for(redirect))
+                        orig_request_qparam = urlencode({"next": str(request.url)})
+                        next_url = "{redirect_path}?{orig_request}".format(
+                            redirect_path=request.url_for(redirect),
+                            orig_request=orig_request_qparam,
+                        )
+                        return RedirectResponse(url=next_url)
                     raise HTTPException(status_code=status_code)
                 return func(*args, **kwargs)
 
diff --git a/tests/test_authentication.py b/tests/test_authentication.py
index 372ea81d8..becb8a54b 100644
--- a/tests/test_authentication.py
+++ b/tests/test_authentication.py
@@ -1,5 +1,6 @@
 import base64
 import binascii
+from urllib.parse import urlencode
 
 import pytest
 
@@ -183,7 +184,10 @@ def test_authentication_redirect():
     with TestClient(app) as client:
         response = client.get("/admin")
         assert response.status_code == 200
-        assert response.url == "http://testserver/"
+        url = "{}?{}".format(
+            "http://testserver/", urlencode({"next": "http://testserver/admin"})
+        )
+        assert response.url == url
 
         response = client.get("/admin", auth=("tomchristie", "example"))
         assert response.status_code == 200
@@ -191,7 +195,10 @@ def test_authentication_redirect():
 
         response = client.get("/admin/sync")
         assert response.status_code == 200
-        assert response.url == "http://testserver/"
+        url = "{}?{}".format(
+            "http://testserver/", urlencode({"next": "http://testserver/admin/sync"})
+        )
+        assert response.url == url
 
         response = client.get("/admin/sync", auth=("tomchristie", "example"))
         assert response.status_code == 200