Changes related to the new ETH interop spec

* RPC requests and responses with a single parameter are now inlined

eth/p2p/p2p_protocol_dsl.nim

@@ -1,5 +1,5 @@
 import
-  options,
+  options, sequtils,
   stew/shims/macros, chronos, faststreams/output_stream
 
 type
@@ -15,7 +15,8 @@ type
     kind*: MessageKind
     procDef*: NimNode
     timeoutParam*: NimNode
-    recIdent*: NimNode
+    recName*: NimNode
+    strongRecName*: NimNode
     recBody*: NimNode
     protocol*: P2PProtocol
     response*: Message
@@ -346,7 +347,7 @@ proc hasReqId*(msg: Message): bool =
 proc ResponderType(msg: Message): NimNode =
   var resp = if msg.kind == msgRequest: msg.response else: msg
   newTree(nnkBracketExpr,
-          msg.protocol.backend.ResponderType, resp.recIdent)
+          msg.protocol.backend.ResponderType, resp.recName)
 
 proc newMsg(protocol: P2PProtocol, kind: MessageKind, id: int,
             procDef: NimNode, timeoutParam: NimNode = nil,
@@ -361,18 +362,35 @@ proc newMsg(protocol: P2PProtocol, kind: MessageKind, id: int,
     msgName = $msgIdent
     recFields = newTree(nnkRecList)
     recBody = newTree(nnkObjectTy, newEmptyNode(), newEmptyNode(), recFields)
-    recName = ident(msgName & "Obj")
+    strongRecName = ident(msgName & "Obj")
+    recName = strongRecName
 
   for param, paramType in procDef.typedParams(skip = 1):
     recFields.add newTree(nnkIdentDefs,
       newTree(nnkPostfix, ident("*"), param), # The fields are public
       chooseFieldType(paramType),             # some types such as openarray
-                                              # are automatically remapped
-      newEmptyNode())
+      newEmptyNode())                         # are automatically remapped
 
-  result = Message(protocol: protocol, id: id, ident: msgIdent, kind: kind,
-                   procDef: procDef, recIdent: recName, recBody: recBody,
-                   timeoutParam: timeoutParam, response: response)
+  if recFields.len == 1:
+    # When we have a single parameter, it's treated as the transferred message
+    # type. `recName` will be resolved to the message type that's intended
+    # for serialization while `strongRecName` will be a distinct type over
+    # which overloads such as `msgId` can be defined. We must use a distinct
+    # type because otherwise Nim may see multiple overloads defined over the
+    # same request parameter type and this will be an ambiguity error.
+    recName = recFields[0][1]
+    recBody = newTree(nnkDistinctTy, recName)
+
+  result = Message(protocol: protocol,
+                   id: id,
+                   ident: msgIdent,
+                   kind: kind,
+                   procDef: procDef,
+                   recName: recName,
+                   strongRecName: strongRecName,
+                   recBody: recBody,
+                   timeoutParam: timeoutParam,
+                   response: response)
 
   if procDef.body.kind != nnkEmpty:
     var userHandler = copy procDef
@@ -482,9 +500,9 @@ proc createSendProc*(msg: Message,
   def[3][0] = if procType == nnkMacroDef:
                 ident "untyped"
               elif msg.kind == msgRequest and not isRawSender:
-                Fut(Opt(msg.response.recIdent))
+                Fut(Opt(msg.response.recName))
               elif msg.kind == msgHandshake and not isRawSender:
-                Fut(msg.recIdent)
+                Fut(msg.recName)
               else:
                 Fut(Void)
 
@@ -518,6 +536,7 @@ proc writeParamsAsRecord*(params: openarray[NimNode],
                              writer, recordWriterCtx,
                              newLit($param), param)
 
+  if params.len > 1:
     result = quote do:
       mixin init, writerType, beginRecord, endRecord
 
@@ -525,6 +544,12 @@ proc writeParamsAsRecord*(params: openarray[NimNode],
       var `recordWriterCtx` = beginRecord(`writer`, `RecordType`)
       `appendParams`
       endRecord(`writer`, `recordWriterCtx`)
+  else:
+    let param = params[0]
+
+    result = quote do:
+      var `writer` = init(WriterType(`Format`), `outputStream`)
+      writeValue(`writer`, `param`)
 
 proc useStandardBody*(sendProc: SendProc,
                       preSerializationStep: proc(stream: NimNode): NimNode,
@@ -537,7 +562,7 @@ proc useStandardBody*(sendProc: SendProc,
 
     initFuture = bindSym "initFuture"
     recipient = sendProc.peerParam
-    msgRecName = msg.recIdent
+    msgRecName = msg.recName
     Format = msg.protocol.backend.SerializationFormat
 
     preSerialization = if preSerializationStep.isNil: newStmtList()
@@ -591,7 +616,7 @@ proc createSerializer*(msg: Message, procType = nnkProcDef): NimNode =
     serializer.msgParams,
     streamVar,
     msg.protocol.backend.SerializationFormat,
-    msg.recIdent)
+    msg.recName)
 
   return serializer.def
 
@@ -612,10 +637,12 @@ proc genAwaitUserHandler*(msg: Message, receivedMsg: NimNode,
 
   var userHandlerCall = newCall(msg.userHandler.name, leadingParams)
 
-  for param, paramType in msg.procDef.typedParams(skip = 1):
-    # If there is user message handler, we'll place a call to it by
-    # unpacking the fields of the received message:
-    userHandlerCall.add newDotExpr(receivedMsg, param)
+  var params = toSeq(msg.procDef.typedParams(skip = 1))
+  if params.len > 1:
+    for p in params:
+      userHandlerCall.add newDotExpr(receivedMsg, p[0])
+  else:
+    userHandlerCall.add receivedMsg
 
   return newCall("await", userHandlerCall)
 
@@ -646,7 +673,7 @@ proc createHandshakeTemplate*(msg: Message,
     peerValue = forwardCall[1]
     timeoutValue = msg.timeoutParam[0]
     peerVarSym = genSym(nskLet, "peer")
-    msgRecName = msg.recIdent
+    msgRecName = msg.recName
 
   forwardCall[1] = peerVarSym
   forwardCall.del(forwardCall.len - 1)
@@ -771,12 +798,13 @@ proc genTypeSection*(p: P2PProtocol): NimNode =
     let
       msgId = msg.id
       msgName = msg.ident
-      msgRecName = msg.recIdent
+      msgRecName = msg.recName
+      msgStrongRecName = msg.strongRecName
       msgRecBody = msg.recBody
 
     result.add quote do:
       # This is a type featuring a single field for each message param:
-      type `msgRecName`* = `msgRecBody`
+      type `msgStrongRecName`* = `msgRecBody`
 
       # Add a helper template for accessing the message type:
       # e.g. p2p.hello:
@@ -784,8 +812,8 @@ proc genTypeSection*(p: P2PProtocol): NimNode =
 
       # Add a helper template for obtaining the message Id for
       # a particular message type:
-      template msgId*(T: type `msgRecName`): int = `msgId`
-      template msgProtocol*(T: type `msgRecName`): type = `protocolName`
+      template msgId*(T: type `msgStrongRecName`): int = `msgId`
+      template msgProtocol*(T: type `msgStrongRecName`): type = `protocolName`
 
 proc genCode*(p: P2PProtocol): NimNode =
   # TODO: try switching to a simpler for msg in p.messages: loop

eth/p2p/rlpx.nim

@@ -609,9 +609,9 @@ proc p2pProtocolBackendImpl*(protocol: P2PProtocol): Backend =
       msgId = msg.id
       msgIdent = msg.ident
       msgName = $msgIdent
-      msgRecName = msg.recIdent
+      msgRecName = msg.recName
       responseMsgId = if msg.response != nil: msg.response.id else: -1
-      ResponseRecord = if msg.response != nil: msg.response.recIdent else: nil
+      ResponseRecord = if msg.response != nil: msg.response.recName else: nil
       hasReqId = msg.hasReqId
       protocol = msg.protocol
       userPragmas = msg.procDef.pragma