start trying to implement tail_call() and set_pipeline()

Author: dwrensha

capnp-rpc/src/local.rs

@@ -126,6 +126,10 @@ impl ResultsHook for Results {
         }
     }
 
+    fn on_tail_call(&mut self) -> Promise<any_pointer::Pipeline, crate::Error> {
+        todo!()
+    }
+
     fn tail_call(self: Box<Self>, _request: Box<dyn RequestHook>) -> Promise<(), Error> {
         unimplemented!()
     }

capnp-rpc/src/rpc.rs

@@ -2176,6 +2176,7 @@ where
     variant: Option<ResultsVariant>,
     redirect_results: bool,
     answer_id: AnswerId,
+    tail_call_pipeline_fulfiller: Option<oneshot::Sender<any_pointer::Pipeline>>,
     finish_received: Rc<Cell<bool>>,
 }
 
@@ -2239,6 +2240,7 @@ where
                 redirect_results,
                 answer_id,
                 finish_received,
+                tail_call_pipeline_fulfiller: None,
             }),
             results_done_fulfiller: Some(fulfiller),
         }
@@ -2293,8 +2295,14 @@ impl<VatId> ResultsHook for Results<VatId> {
         }
     }
 
-    fn tail_call(self: Box<Self>, _request: Box<dyn RequestHook>) -> Promise<(), Error> {
-        unimplemented!()
+    fn on_tail_call(&mut self) -> Promise<any_pointer::Pipeline, crate::Error> {
+        todo!()
+    }
+
+    fn tail_call(self: Box<Self>, request: Box<dyn RequestHook>) -> Promise<(), Error> {
+        let (promise, pipeline) = self.direct_tail_call(request);
+        // TODO somehow send pipeline to tail_call_pipeline_fulfiller
+        promise
     }
 
     fn direct_tail_call(

capnp/src/capability.rs

@@ -239,6 +239,12 @@ where
     pub fn set(&mut self, other: T::Reader<'_>) -> crate::Result<()> {
         self.hook.get().unwrap().set_as(other)
     }
+
+    pub fn tail_call<SubParams>(self, tail_request: Request<SubParams, T>)
+                                -> Promise<(), Error>
+    {
+        self.hook.tail_call(tail_request.hook)
+    }
 }
 
 pub trait FromTypelessPipeline {

capnp/src/private/capability.rs

@@ -94,6 +94,9 @@ impl Clone for Box<dyn ClientHook> {
 pub trait ResultsHook {
     fn get(&mut self) -> crate::Result<any_pointer::Builder<'_>>;
     fn allow_cancellation(&self);
+
+    fn on_tail_call(&mut self) -> Promise<any_pointer::Pipeline, crate::Error>;
+
     fn tail_call(self: Box<Self>, request: Box<dyn RequestHook>) -> Promise<(), crate::Error>;
     fn direct_tail_call(
         self: Box<Self>,