Agnostic approach to construct context from_dict

Replace the existing argument specified values in from_dict() method
to be argument agnostic for any future arguments. Based from version
found in Solum.

All current boolean values match instantiation defaults.

Change-Id: I17c76881aa662de7ff245b3f6bfca309896ddf24

oslo_context/context.py

@@ -26,6 +26,7 @@ context or provide additional information in their specific WSGI pipeline
 or logging context.
 """
 
+import inspect
 import itertools
 import threading
 import uuid
@@ -114,20 +115,13 @@ class RequestContext(object):
         return values
 
     @classmethod
-    def from_dict(cls, ctx):
+    def from_dict(cls, values):
         """Construct a context object from a provided dictionary."""
-        return cls(
-            auth_token=ctx.get("auth_token"),
-            user=ctx.get("user"),
-            tenant=ctx.get("tenant"),
-            domain=ctx.get("domain"),
-            user_domain=ctx.get("user_domain"),
-            project_domain=ctx.get("project_domain"),
-            is_admin=ctx.get("is_admin", False),
-            read_only=ctx.get("read_only", False),
-            show_deleted=ctx.get("show_deleted", False),
-            request_id=ctx.get("request_id"),
-            resource_uuid=ctx.get("resource_uuid"))
+        allowed = [arg for arg in
+                   inspect.getargspec(RequestContext.__init__).args
+                   if arg != 'self']
+        kwargs = {k: v for (k, v) in values.items() if k in allowed}
+        return cls(**kwargs)
 
     @classmethod
     def from_environ(cls, environ, **kwargs):

oslo_context/tests/test_context.py

@@ -104,6 +104,23 @@ class ContextTest(test_base.BaseTestCase):
         self.assertEqual("request1", ctx.request_id)
         self.assertEqual("instance1", ctx.resource_uuid)
 
+    def test_from_dict_unknown_keys(self):
+        dct = {
+            "auth_token": "token1",
+            "user": "user1",
+            "read_only": True,
+            "roles": "role1,role2,role3",  # future review provides this
+            "color": "red",
+            "unknown": ""
+        }
+        ctx = context.RequestContext.from_dict(dct)
+        self.assertEqual("token1", ctx.auth_token)
+        self.assertEqual("user1", ctx.user)
+        self.assertIsNone(ctx.tenant)
+        self.assertFalse(ctx.is_admin)
+        self.assertTrue(ctx.read_only)
+        self.assertRaises(KeyError, lambda: ctx.__dict__['color'])
+
     def test_is_user_context(self):
         self.assertFalse(context.is_user_context(None))
         ctx = context.RequestContext(is_admin=True)