Add schema to ObtainAuthToken

Add encoding parameter to ManualSchema

Closes #5676

* Fixed lint errors
* Added docs for ManualSchema encoding parameter

docs/api-guide/schemas.md

@@ -669,6 +669,8 @@ The `ManualSchema` constructor takes two arguments:
 
 **`description`**: A string description. Optional.
 
+**`encoding`**: Default `None`. A string encoding, e.g `application/json`. Optional.
+
 ---
 
 ## Core API

rest_framework/authtoken/views.py

@@ -3,6 +3,9 @@ from rest_framework.authtoken.models import Token
 from rest_framework.authtoken.serializers import AuthTokenSerializer
 from rest_framework.response import Response
 from rest_framework.views import APIView
+from rest_framework.schemas import ManualSchema
+import coreapi
+import coreschema
 
 
 class ObtainAuthToken(APIView):
@@ -11,6 +14,29 @@ class ObtainAuthToken(APIView):
     parser_classes = (parsers.FormParser, parsers.MultiPartParser, parsers.JSONParser,)
     renderer_classes = (renderers.JSONRenderer,)
     serializer_class = AuthTokenSerializer
+    schema = ManualSchema(
+        fields=[
+            coreapi.Field(
+                name="username",
+                required=True,
+                location='form',
+                schema=coreschema.String(
+                    title="Username",
+                    description="Valid username for authentication",
+                ),
+            ),
+            coreapi.Field(
+                name="password",
+                required=True,
+                location='form',
+                schema=coreschema.String(
+                    title="Password",
+                    description="Valid password for authentication",
+                ),
+            ),
+        ],
+        encoding="application/json",
+    )
 
     def post(self, request, *args, **kwargs):
         serializer = self.serializer_class(data=request.data,

rest_framework/schemas/inspectors.py

@@ -445,7 +445,7 @@ class ManualSchema(ViewInspector):
     Allows providing a list of coreapi.Fields,
     plus an optional description.
     """
-    def __init__(self, fields, description=''):
+    def __init__(self, fields, description='', encoding=None):
         """
         Parameters:
 
@@ -455,6 +455,7 @@ class ManualSchema(ViewInspector):
         assert all(isinstance(f, coreapi.Field) for f in fields), "`fields` must be a list of coreapi.Field instances"
         self._fields = fields
         self._description = description
+        self._encoding = encoding
 
     def get_link(self, path, method, base_url):
 
@@ -464,7 +465,7 @@ class ManualSchema(ViewInspector):
         return coreapi.Link(
             url=urlparse.urljoin(base_url, path),
             action=method.lower(),
-            encoding=None,
+            encoding=self._encoding,
             fields=self._fields,
             description=self._description
         )