Make rpc transform use async

eth-rpc/server/rpcregistration.nim

@@ -1,10 +1,14 @@
-import macros, servertypes
+import macros, servertypes, strutils
 
 var rpcCallRefs {.compiletime.} = newSeq[(string)]()
 
 macro rpc*(prc: untyped): untyped =
-  # REVIEW: (IMPORTANT) I think the rpc procs should be async.
-  # they may need to call into other async procs of the VM
+  ## Converts a procedure into the following format:
+  ##  <proc name>*(params: JsonNode): Future[JsonNode] {.async.}
+  ## This procedure is then added into a compile-time list
+  ## so that it is automatically registered for every server that
+  ## calls registerRpcs(server)
+  prc.expectKind nnkProcDef
   result = prc
   let
     params = prc.findChild(it.kind == nnkFormalParams)
@@ -20,8 +24,13 @@ macro rpc*(prc: untyped): untyped =
   identDefs.add ident("params"), ident("JsonNode"), newEmptyNode()
   # check there isn't already a result type
   assert params.len == 1 and params[0].kind == nnkEmpty
-  params[0] = ident("JsonNode")
+  params[0] = newNimNode(nnkBracketExpr)
+  params[0].add ident("Future"), ident("JsonNode")
   params.add identDefs
+  # add async pragma, we can assume there isn't an existing .async.
+  # as this would fail the result check above.
+  prc.addPragma(newIdentNode("async"))
+
   # Adds to compiletime list of rpc calls so we can register them in bulk
   # for multiple servers using `registerRpcs`.
   rpcCallRefs.add $procName
@@ -33,3 +42,4 @@ macro registerRpcs*(server: RpcServer): untyped =
   for procName in rpcCallRefs:
     let de = newDotExpr(ident($server), ident("register"))
     result.add(newCall(de, newStrLitNode(procName), ident(procName)))
+  echo result.repr

eth-rpc/server/serverdispatch.nim

@@ -20,7 +20,7 @@ proc processMessage(server: RpcServer, client: AsyncSocket, line: string) {.asyn
     if not server.procs.hasKey(methodName):
       await client.sendError(METHOD_NOT_FOUND, "Method not found", id, %(methodName & " is not a registered method."))
     else:
-      let callRes = server.procs[methodName](node["params"])
+      let callRes = await server.procs[methodName](node["params"])
       await client.send($wrapReply(id, callRes, newJNull()) & "\c\l")
 
 proc processClient(server: RpcServer, client: AsyncSocket) {.async.} =
@@ -33,12 +33,11 @@ proc processClient(server: RpcServer, client: AsyncSocket) {.async.} =
 
     ifDebug: echo "Process client: ", server.port, ":" & line
 
-    let fut = processMessage(server, client, line)
-    await fut
-    if fut.failed:
-      if fut.readError of RpcProcError:
-        # TODO: Currently exceptions in rpc calls are not properly handled
-        let err = fut.readError.RpcProcError
+    let future = processMessage(server, client, line)
+    await future
+    if future.failed:
+      if future.readError of RpcProcError:
+        let err = future.readError.RpcProcError
         await client.sendError(err.code, err.msg, err.data)
       else:
         await client.sendError(-32000, "Error", %getCurrentExceptionMsg())

eth-rpc/server/servertypes.nim

@@ -1,7 +1,7 @@
 import asyncdispatch, asyncnet, json, tables
 
 type
-  RpcProc* = proc (params: JsonNode): JsonNode
+  RpcProc* = proc (params: JsonNode): Future[JsonNode]
 
   RpcServer* = ref object
     socket*: AsyncSocket