Pipelining almost completely wrapped

Waiting on some upstream changes in C++ libcapnp before I can finish

capnp/asyncHelper.h

@@ -1,51 +0,0 @@
-#include "kj/async.h"
-#include "Python.h"
-
-extern "C" {
-   PyObject * wrap_kj_exception(kj::Exception &);
-   // void _gevent_eventloop_prepare_to_sleep();
-   // void _gevent_eventloop_sleep();
-   // void _gevent_eventloop_wake();
-}
-
-PyObject * wrapPyFunc(PyObject * func, PyObject * arg) {
-    PyObject * result = PyObject_CallFunctionObjArgs(func, arg, NULL);
-    Py_DECREF(func);
-    return result;
-}
-
-::kj::Promise<PyObject *> evalLater(kj::EventLoop & loop, PyObject * func) {
-  return loop.evalLater([func]() { return wrapPyFunc(func, NULL); } );
-}
-
-::kj::Promise<PyObject *> there(kj::EventLoop & loop, kj::Promise<PyObject *> & promise, PyObject * func, PyObject * error_func) {
-  if(error_func == Py_None)
-    return loop.there(kj::mv(promise), [func](PyObject * arg) { return wrapPyFunc(func, arg); } );
-  else
-    return loop.there(kj::mv(promise), [func](PyObject * arg) { return wrapPyFunc(func, arg); } 
-                                     , [error_func](kj::Exception arg) { return wrapPyFunc(error_func, wrap_kj_exception(arg)); } );
-}
-::kj::Promise<PyObject *> then(kj::Promise<PyObject *> & promise, PyObject * func, PyObject * error_func) {
-  if(error_func == Py_None)
-    return promise.then([func](PyObject * arg) { return wrapPyFunc(func, arg); } );
-  else
-    return promise.then([func](PyObject * arg) { return wrapPyFunc(func, arg); } 
-                                     , [error_func](kj::Exception arg) { return wrapPyFunc(error_func, wrap_kj_exception(arg)); } );
-}
-
-// class PyEventLoop final: public ::kj::EventLoop {
-// public:
-//   PyEventLoop() {}
-//   ~PyEventLoop() noexcept(false) {}
-
-// protected:
-//   void prepareToSleep() noexcept override {
-//     _gevent_eventloop_prepare_to_sleep();
-//   }
-//   void sleep() override {
-//     _gevent_eventloop_sleep();
-//   }
-//   void wake() const override {
-//     _gevent_eventloop_wake();
-//   }
-// };

capnp/asyncHelper_cpp.pxd

@@ -1,14 +0,0 @@
-# schema.capnp.cpp.pyx
-# distutils: language = c++
-# distutils: extra_compile_args = --std=c++11
-
-from cpython.ref cimport PyObject
-from capnp_cpp cimport PyPromise, EventLoop
-
-cdef extern from "asyncHelper.h":
-    PyPromise evalLater(EventLoop &, PyObject * func)
-    PyPromise there(EventLoop & loop, PyPromise & promise, PyObject * func, PyObject * error_func)
-    PyPromise then(PyPromise & promise, PyObject * func, PyObject * error_func)
-
-    # cdef cppclass PyEventLoop(EventLoop):
-    #     pass

capnp/async_cpp.pxd

@@ -15,6 +15,7 @@ cdef extern from "kj/async.h" namespace " ::kj":
         T wait()
 
 ctypedef Promise[PyObject *] PyPromise
+ctypedef Promise[void] VoidPromise
 
 cdef extern from "kj/async.h" namespace " ::kj":
     cdef cppclass EventLoop:

capnp/capabilityHelper.h

@@ -4,10 +4,46 @@
 #include <iostream>
 
 extern "C" {
+   void wrap_remote_call(PyObject * func, capnp::Response<capnp::DynamicStruct> &);
    PyObject * wrap_dynamic_struct_reader(capnp::DynamicStruct::Reader &);
-   void call_server_method(PyObject * py_server, char * name, capnp::CallContext< capnp::DynamicStruct, capnp::DynamicStruct> & context);
+   ::kj::Promise<void> * call_server_method(PyObject * py_server, char * name, capnp::CallContext< capnp::DynamicStruct, capnp::DynamicStruct> & context);
+   PyObject * wrap_kj_exception(kj::Exception &);
  }
 
+PyObject * wrapPyFunc(PyObject * func, PyObject * arg) {
+    PyObject * result = PyObject_CallFunctionObjArgs(func, arg, NULL);
+    Py_DECREF(func);
+    return result;
+}
+
+::kj::Promise<PyObject *> evalLater(kj::EventLoop & loop, PyObject * func) {
+  return loop.evalLater([func]() { return wrapPyFunc(func, NULL); } );
+}
+
+::kj::Promise<PyObject *> there(kj::EventLoop & loop, kj::Promise<PyObject *> & promise, PyObject * func, PyObject * error_func) {
+  if(error_func == Py_None)
+    return loop.there(kj::mv(promise), [func](PyObject * arg) { return wrapPyFunc(func, arg); } );
+  else
+    return loop.there(kj::mv(promise), [func](PyObject * arg) { return wrapPyFunc(func, arg); } 
+                                     , [error_func](kj::Exception arg) { return wrapPyFunc(error_func, wrap_kj_exception(arg)); } );
+}
+
+::kj::Promise<PyObject *> then(kj::Promise<PyObject *> & promise, PyObject * func, PyObject * error_func) {
+  if(error_func == Py_None)
+    return promise.then([func](PyObject * arg) { return wrapPyFunc(func, arg); } );
+  else
+    return promise.then([func](PyObject * arg) { return wrapPyFunc(func, arg); } 
+                                     , [error_func](kj::Exception arg) { return wrapPyFunc(error_func, wrap_kj_exception(arg)); } );
+}
+
+::kj::Promise<void> then(::capnp::RemotePromise< ::capnp::DynamicStruct> & promise, PyObject * func, PyObject * error_func) {
+  if(error_func == Py_None)
+    return promise.then([func](capnp::Response<capnp::DynamicStruct>&& arg) { wrap_remote_call(func, arg); } );
+  else
+    return promise.then([func](capnp::Response<capnp::DynamicStruct>&& arg) { wrap_remote_call(func, arg); } 
+                                     , [error_func](kj::Exception arg) { wrapPyFunc(error_func, wrap_kj_exception(arg)); } );
+}
+
 class PythonInterfaceDynamicImpl final: public capnp::DynamicCapability::Server {
 public:
   PyObject * py_server;
@@ -24,8 +60,13 @@ public:
   kj::Promise<void> call(capnp::InterfaceSchema::Method method,
                          capnp::CallContext< capnp::DynamicStruct, capnp::DynamicStruct> context) {
     auto methodName = method.getProto().getName();
-    call_server_method(py_server, const_cast<char *>(methodName.cStr()), context);
-    return kj::READY_NOW;
+    kj::Promise<void> * promise = call_server_method(py_server, const_cast<char *>(methodName.cStr()), context);
+    if(promise == nullptr)
+      return kj::READY_NOW;
+
+    kj::Promise<void> ret(kj::mv(*promise));
+    delete promise;
+    return ret;
   }
 };
 

capnp/capnp.pyx

@@ -9,7 +9,7 @@
 cimport cython
 cimport capnp_cpp as capnp
 cimport schema_cpp
-from capnp_cpp cimport Schema as C_Schema, StructSchema as C_StructSchema, InterfaceSchema as C_InterfaceSchema, DynamicStruct as C_DynamicStruct, DynamicValue as C_DynamicValue, Type as C_Type, DynamicList as C_DynamicList, fixMaybe, getEnumString, SchemaParser as C_SchemaParser, ParsedSchema as C_ParsedSchema, VOID, ArrayPtr, StringPtr, String, StringTree, DynamicOrphan as C_DynamicOrphan, ObjectPointer as C_DynamicObject, WordArrayPtr, DynamicCapability as C_DynamicCapability, new_client, Request, Response, RemotePromise, convert_to_pypromise, SimpleEventLoop, PyPromise, CallContext
+from capnp_cpp cimport Schema as C_Schema, StructSchema as C_StructSchema, InterfaceSchema as C_InterfaceSchema, DynamicStruct as C_DynamicStruct, DynamicValue as C_DynamicValue, Type as C_Type, DynamicList as C_DynamicList, fixMaybe, getEnumString, SchemaParser as C_SchemaParser, ParsedSchema as C_ParsedSchema, VOID, ArrayPtr, StringPtr, String, StringTree, DynamicOrphan as C_DynamicOrphan, ObjectPointer as C_DynamicObject, WordArrayPtr, DynamicCapability as C_DynamicCapability, new_client, Request, Response, RemotePromise, convert_to_pypromise, SimpleEventLoop, PyPromise, VoidPromise, CallContext
 
 from schema_cpp cimport Node as C_Node, EnumNode as C_EnumNode
 from cython.operator cimport dereference as deref
@@ -44,14 +44,28 @@ from functools import partial as _partial
 cdef public object wrap_dynamic_struct_reader(C_DynamicStruct.Reader & reader):
     return _DynamicStructReader()._init(reader, None)
 
-cdef public void call_server_method(PyObject * _server, char * _method_name, CallContext & _context):
+cdef public void wrap_remote_call(PyObject * func, Response & r):
+    response = _Response()._init_childptr(new Response(moveResponse(r)), None)
+
+    func_obj = <object>func
+    # TODO: decref func?
+    func_obj(response)
+
+cdef public VoidPromise * call_server_method(PyObject * _server, char * _method_name, CallContext & _context):
     server = <object>_server
     method_name = <object>_method_name
 
     context = _CallContext()._init(_context)
-    getattr(server, method_name)(context)
+    ret = getattr(server, method_name)(context)
 
-# By making it public, we'll be able to call it from asyncHelper.h
+    if ret is not None:
+        if type(ret) is _VoidPromise:
+            return new VoidPromise(moveVoidPromise(deref((<_VoidPromise>ret).thisptr)))
+        else:
+            raise ValueError('Server function returned a value that was not a VoidPromise: ' + str(ret))
+
+    return NULL
+    
 cdef public object wrap_kj_exception(capnp.Exception & exception):
     return None # TODO
 
@@ -103,6 +117,7 @@ cdef extern from "<utility>" namespace "std":
     Request moveRequest"std::move"(Request)
     Response moveResponse"std::move"(Response)
     PyPromise movePromise"std::move"(PyPromise)
+    VoidPromise moveVoidPromise"std::move"(VoidPromise)
     RemotePromise moveRemotePromise"std::move"(RemotePromise)
     CallContext moveCallContext"std::move"(CallContext)
 
@@ -301,8 +316,6 @@ cdef class _DynamicListBuilder:
         return self._get(index)
 
     def __setitem__(self, index, value):
-        # TODO: share code with _DynamicStructBuilder.__setattr__
-        
         size = self.thisptr.size()
         if index >= size:
             raise IndexError('Out of bounds')
@@ -387,6 +400,8 @@ cdef to_python_reader(C_DynamicValue.Reader self, object parent):
         return None
     elif type == capnp.TYPE_OBJECT:
         return _DynamicObjectReader()._init(self.asObject(), parent)
+    elif type == capnp.TYPE_CAPABILITY:
+        return _DynamicCapabilityClient()._init(self.asCapability(), parent)
     elif type == capnp.TYPE_UNKNOWN:
         raise ValueError("Cannot convert type to Python. Type is unknown by capnproto library")
     else:
@@ -417,6 +432,8 @@ cdef to_python_builder(C_DynamicValue.Builder self, object parent):
         return None
     elif type == capnp.TYPE_OBJECT:
         return _DynamicObjectBuilder()._init(self.asObject(), parent)
+    elif type == capnp.TYPE_CAPABILITY:
+        return _DynamicCapabilityClient()._init(self.asCapability(), parent)
     elif type == capnp.TYPE_UNKNOWN:
         raise ValueError("Cannot convert type to Python. Type is unknown by capnproto library")
     else:
@@ -428,6 +445,9 @@ cdef C_DynamicValue.Reader _extract_dynamic_struct_builder(_DynamicStructBuilder
 cdef C_DynamicValue.Reader _extract_dynamic_struct_reader(_DynamicStructReader value):
     return C_DynamicValue.Reader(value.thisptr)
 
+cdef C_DynamicValue.Reader _extract_dynamic_client(_DynamicCapabilityClient value):
+    return C_DynamicValue.Reader(value.thisptr)
+
 cdef _setDynamicField(_DynamicSetterClasses thisptr, field, value, parent):
     cdef C_DynamicValue.Reader temp
     value_type = type(value)
@@ -458,6 +478,8 @@ cdef _setDynamicField(_DynamicSetterClasses thisptr, field, value, parent):
         thisptr.set(field, _extract_dynamic_struct_builder(value))
     elif value_type is _DynamicStructReader:
         thisptr.set(field, _extract_dynamic_struct_reader(value))
+    elif value_type is _DynamicCapabilityClient:
+        thisptr.set(field, _extract_dynamic_client(value))
     else:
         raise ValueError("Non primitive type")
 
@@ -491,6 +513,8 @@ cdef _setDynamicFieldPtr(_DynamicSetterClasses * thisptr, field, value, parent):
         thisptr.set(field, _extract_dynamic_struct_builder(value))
     elif value_type is _DynamicStructReader:
         thisptr.set(field, _extract_dynamic_struct_reader(value))
+    elif value_type is _DynamicCapabilityClient:
+        thisptr.set(field, _extract_dynamic_client(value))
     else:
         raise ValueError("Non primitive type")
 
@@ -898,6 +922,7 @@ cdef class _CallContext:
 
 cdef class Promise:
     cdef PyPromise * thisptr
+    cdef public bint is_consumed
 
     def __init__(self):
         self.is_consumed = True
@@ -928,6 +953,38 @@ cdef class Promise:
 
         return Promise()._init(capnp.then(deref(self.thisptr), <PyObject *>func, <PyObject *>error_func))
 
+cdef class _VoidPromise:
+    cdef VoidPromise * thisptr
+    cdef public bint is_consumed
+
+    def __init__(self):
+        self.is_consumed = True
+
+    cdef _init(self, VoidPromise other):
+        self.is_consumed = False
+        self.thisptr = new VoidPromise(moveVoidPromise(other))
+        return self
+
+    def __dealloc__(self):
+        del self.thisptr
+
+    cpdef wait(self) except+:
+        if self.is_consumed:
+            raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
+
+        self.thisptr.wait()
+        self.is_consumed = True
+
+
+    # cpdef then(self, func, error_func=None) except+:
+    #     if self.is_consumed:
+    #         raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
+
+    #     Py_INCREF(func)
+    #     Py_INCREF(error_func)
+
+    #     return Promise()._init(capnp.then(deref(self.thisptr), <PyObject *>func, <PyObject *>error_func))
+
 cdef class _RemotePromise:
     cdef RemotePromise * thisptr
     cdef public bint is_consumed
@@ -957,14 +1014,28 @@ cdef class _RemotePromise:
     cpdef as_pypromise(self) except +:
         Promise()._init(convert_to_pypromise(deref(self.thisptr)))
 
-    # cpdef then(self, func, error_func=None) except+:
-    #     if self.is_consumed:
-    #         raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
+    cpdef then(self, func, error_func=None) except+:
+        if self.is_consumed:
+            raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
 
-    #     Py_INCREF(func)
-    #     Py_INCREF(error_func)
+        Py_INCREF(func)
+        Py_INCREF(error_func)
 
-    #     return _RemotePromise()._init(capnp.then(deref(self.thisptr), <PyObject *>func, <PyObject *>error_func))
+        return _VoidPromise()._init(capnp.then(deref(self.thisptr), <PyObject *>func, <PyObject *>error_func))
+
+    cpdef _get(self, field) except +ValueError:
+        return _DynamicCapabilityClient()._init((<C_DynamicValue.Pipeline>self.thisptr.get(field)).asCapability(), self._parent)
+
+    def __getattr__(self, field):
+        return self._get(field)
+
+    property schema:
+        """A property that returns the _StructSchema object matching this reader"""
+        def __get__(self):
+            return _StructSchema()._init(self.thisptr.getSchema())
+
+    def __dir__(self):
+        return list(self.schema.fieldnames)
 
 cdef class EventLoop:
     cdef SimpleEventLoop thisptr
@@ -1008,11 +1079,21 @@ cdef class _Response(_DynamicStructReader):
         self._init(<C_DynamicStruct.Reader>deref(self.thisptr_child), parent)
         return self
 
+    cdef _init_childptr(self, Response * other, parent):
+        self.thisptr_child = other
+        self._init(<C_DynamicStruct.Reader>deref(self.thisptr_child), parent)
+        return self
+
 cdef class _DynamicCapabilityClient:
     cdef C_DynamicCapability.Client thisptr
-    cdef public object _event_loop, _server
+    cdef public object _event_loop, _server, _parent
 
-    def __init__(self, schema, server, event_loop):
+    cdef _init(self, C_DynamicCapability.Client other, object parent):
+        self.thisptr = other
+        self._parent = parent
+        return self
+
+    cdef _init_vals(self, schema, server, event_loop):
         cdef _InterfaceSchema s
         if hasattr(schema, 'schema'):
             s = schema.schema
@@ -1023,6 +1104,7 @@ cdef class _DynamicCapabilityClient:
         self._event_loop = event_loop
         self.thisptr = new_client(s.thisptr, <PyObject *>server, loop.thisptr)
         self._server = server
+        return self
 
     cpdef _send_helper(self, name, firstSegmentWordSize, kwargs) except +ValueError:
         cdef Request * request = new Request(self.thisptr.newRequest(name, firstSegmentWordSize))
@@ -1287,7 +1369,7 @@ cdef class SchemaParser:
                 elif proto.isInterface:
                     def new_client(bound_local_module):
                         def helper(server, loop):
-                            return _DynamicCapabilityClient(bound_local_module, server, loop)
+                            return _DynamicCapabilityClient()._init_vals(bound_local_module, server, loop)
                         return helper
                     local_module.schema = schema.as_interface()
                     local_module.new_client = new_client(local_module)

capnp/capnp_cpp.pxd

@@ -2,7 +2,7 @@
 # distutils: language = c++
 # distutils: extra_compile_args = --std=c++11
 from schema_cpp cimport Node, Data, StructNode, EnumNode
-from async_cpp cimport PyPromise, Promise
+from async_cpp cimport PyPromise, VoidPromise, Promise
 
 from cpython.ref cimport PyObject
 from libc.stdint cimport *
@@ -112,6 +112,8 @@ cdef extern from "capnp/dynamic.h" namespace " ::capnp":
             pass
         cppclass Builder:
             pass
+        cppclass Pipeline:
+            pass
 
     enum Type:
         TYPE_UNKNOWN " ::capnp::DynamicValue::UNKNOWN"
@@ -147,11 +149,14 @@ cdef extern from "capnp/dynamic.h" namespace " ::capnp":
             void adopt(char *, DynamicOrphan) except +ValueError
             DynamicOrphan disown(char *)
             DynamicStruct.Reader asReader()
+        cppclass Pipeline:
+            DynamicValueForward.Pipeline get(char *)
+            StructSchema getSchema()
 
 cdef extern from "capnp/capability.h" namespace " ::capnp":
     cdef cppclass Response" ::capnp::Response< ::capnp::DynamicStruct>"(DynamicStruct.Reader):
         Response(Response)
-    cdef cppclass RemotePromise" ::capnp::RemotePromise< ::capnp::DynamicStruct>"(Promise[Response]):
+    cdef cppclass RemotePromise" ::capnp::RemotePromise< ::capnp::DynamicStruct>"(Promise[Response], DynamicStruct.Pipeline):
         RemotePromise(RemotePromise)
 
 cdef extern from "capnp/dynamic.h" namespace " ::capnp":
@@ -189,6 +194,10 @@ cdef extern from "fixMaybe.h":
 
 
 cdef extern from "capabilityHelper.h":
+    PyPromise evalLater(EventLoop &, PyObject * func)
+    PyPromise there(EventLoop & loop, PyPromise & promise, PyObject * func, PyObject * error_func)
+    PyPromise then(PyPromise & promise, PyObject * func, PyObject * error_func)
+    VoidPromise then(RemotePromise & promise, PyObject * func, PyObject * error_func)
     cppclass PythonInterfaceDynamicImpl:
         pass
     DynamicCapability.Client new_client(InterfaceSchema&, PyObject *, EventLoop&)
@@ -235,6 +244,7 @@ cdef extern from "capnp/dynamic.h" namespace " ::capnp":
             Reader(DynamicList.Reader& value)
             Reader(DynamicEnum value)
             Reader(DynamicStruct.Reader& value)
+            Reader(DynamicCapability.Client& value)
             Type getType()
             int64_t asInt"as<int64_t>"()
             uint64_t asUint"as<uint64_t>"()
@@ -244,6 +254,7 @@ cdef extern from "capnp/dynamic.h" namespace " ::capnp":
             DynamicList.Reader asList"as< ::capnp::DynamicList>"()
             DynamicStruct.Reader asStruct"as< ::capnp::DynamicStruct>"()
             ObjectPointer.Reader asObject"as< ::capnp::ObjectPointer>"()
+            DynamicCapability.Client asCapability"as< ::capnp::DynamicCapability>"()
             DynamicEnum asEnum"as< ::capnp::DynamicEnum>"()
             Data.Reader asData"as< ::capnp::Data>"()
 
@@ -257,9 +268,14 @@ cdef extern from "capnp/dynamic.h" namespace " ::capnp":
             DynamicList.Builder asList"as< ::capnp::DynamicList>"()
             DynamicStruct.Builder asStruct"as< ::capnp::DynamicStruct>"()
             ObjectPointer.Builder asObject"as< ::capnp::ObjectPointer>"()
+            DynamicCapability.Client asCapability"as< ::capnp::DynamicCapability>"()
             DynamicEnum asEnum"as< ::capnp::DynamicEnum>"()
             Data.Builder asData"as< ::capnp::Data>"()
 
+        cppclass Pipeline:
+            Pipeline(Pipeline)
+            DynamicCapability.Client asCapability"releaseAs< ::capnp::DynamicCapability>"()
+
 cdef extern from "capnp/schema-parser.h" namespace " ::capnp":
     cdef cppclass ParsedSchema(Schema):
         ParsedSchema getNested(char * name) except +
@@ -297,8 +313,3 @@ cdef extern from "kj/async.h" namespace " ::kj":
         PyPromise there(PyPromise, PyObject * func)
     cdef cppclass SimpleEventLoop(EventLoop):
         pass
-
-cdef extern from "asyncHelper.h":
-    PyPromise evalLater(EventLoop &, PyObject * func)
-    PyPromise there(EventLoop & loop, PyPromise & promise, PyObject * func, PyObject * error_func)
-    PyPromise then(PyPromise & promise, PyObject * func, PyObject * error_func)

test/test_capability.capnp

@@ -35,11 +35,11 @@ interface TestInterface {
 #   grault @2 () -> TestAllTypes;
 # }
 
-# interface TestPipeline {
-#   getCap @0 (n: UInt32, inCap :TestInterface) -> (s: Text, outBox :Box);
-#   testPointers @1 (cap :TestInterface, obj :Object, list :List(TestInterface)) -> ();
+interface TestPipeline {
+  getCap @0 (n: UInt32, inCap :TestInterface) -> (s: Text, outBox :Box);
+  testPointers @1 (cap :TestInterface, obj :Object, list :List(TestInterface)) -> ();
 
-#   struct Box {
-#     cap @0 :TestInterface;
-#   }
-# }
+  struct Box {
+    cap @0 :TestInterface;
+  }
+}

test/test_capability.py

@@ -9,10 +9,21 @@ def capability():
      return capnp.load(os.path.join(this_dir, 'test_capability.capnp'))
 
 class Server:
-    def foo(self, context):
-        context.results.x = str(context.params.i * 5 + 1)
+    def __init__(self, val=1):
+        self.val = val
 
-def test_basic_client(capability):
+    def foo(self, context):
+        context.results.x = str(context.params.i * 5 + self.val)
+
+class PipelineServer:
+    def getCap(self, context):
+        def _then(response):
+            context.results.s = response.x + '_foo'
+            context.results.outBox.outCap = Server(100)
+
+        return context.params.inCap.foo(i=context.params.n).then(_then)
+
+def test_client(capability):
     loop = capnp.EventLoop()
 
     client = capability.TestInterface.new_client(Server(), loop)
@@ -70,3 +81,16 @@ def test_simple_client(capability):
 
     with pytest.raises(ValueError):
         remote = client.foo(baz=5)
+
+def test_pipeline(capability):
+    loop = capnp.EventLoop()
+
+    client = capability.TestPipeline.new_client(PipelineServer(), loop)
+    foo_client = capability.TestInterface.new_client(Server(), loop)
+
+    remote = client.getCap(n=5, inCap=foo_client)
+    response = loop.wait_remote(remote)
+
+    assert response.s == '26_foo'
+
+