From 6535b39e47bf2dfbba0457b96ccabdd75a1e189a Mon Sep 17 00:00:00 2001
From: Kim De Mey <kim.demey@gmail.com>
Date: Wed, 23 Aug 2023 18:03:09 +0200
Subject: [PATCH] Add SszError to message decoding result (#1660)

This allows for improved error messages. Required changing the PortalResult from cstring to string for the error.
---
 fluffy/network/wire/messages.nim        | 10 +++++-----
 fluffy/network/wire/portal_protocol.nim |  9 +++++----
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/fluffy/network/wire/messages.nim b/fluffy/network/wire/messages.nim
index e49d3d20f..748400dce 100644
--- a/fluffy/network/wire/messages.nim
+++ b/fluffy/network/wire/messages.nim
@@ -142,16 +142,16 @@ func encodeMessage*[T: SomeMessage](m: T): seq[byte] =
   elif T is OfferMessage: SSZ.encode(Message(kind: offer, offer: m))
   elif T is AcceptMessage: SSZ.encode(Message(kind: accept, accept: m))
 
-func decodeMessage*(body: openArray[byte]): Result[Message, cstring] =
+func decodeMessage*(body: openArray[byte]): Result[Message, string] =
   try:
     if body.len < 1: # TODO: This check should probably move a layer down
       return err("No message data, peer might not support this talk protocol")
     ok(SSZ.decode(body, Message))
-  except SszError:
-    err("Invalid message encoding")
+  except SszError as e:
+    err("Invalid message encoding: " & e.msg)
 
 template innerMessage[T: SomeMessage](
-    message: Message, expected: MessageKind): Result[T, cstring] =
+    message: Message, expected: MessageKind): Result[T, string] =
   if (message.kind == expected):
     ok(message.expected)
   else:
@@ -160,7 +160,7 @@ template innerMessage[T: SomeMessage](
 # Each `Message` variants corresponds to an MessageKind. Therefore, the inner
 # message can be extracted when providing the expected message type T.
 # If the message does not hold the expacted variant, return error.
-func getInnerMessage*[T: SomeMessage](m: Message): Result[T, cstring] =
+func getInnerMessage*[T: SomeMessage](m: Message): Result[T, string] =
   innerMessage[T](m, messageKind(T))
 
 func getTalkReqOverhead*(protocolIdLen: int): int =
diff --git a/fluffy/network/wire/portal_protocol.nim b/fluffy/network/wire/portal_protocol.nim
index df6b0eb6c..5c96b7e76 100644
--- a/fluffy/network/wire/portal_protocol.nim
+++ b/fluffy/network/wire/portal_protocol.nim
@@ -171,7 +171,7 @@ type
     offerQueue: AsyncQueue[OfferRequest]
     offerWorkers: seq[Future[void]]
 
-  PortalResult*[T] = Result[T, cstring]
+  PortalResult*[T] = Result[T, string]
 
   FoundContentKind* = enum
     Nodes,
@@ -495,9 +495,10 @@ proc reqResponse[Request: SomeMessage, Response: SomeMessage](
   # not supporting the specific talk protocol, as according to specification
   # an empty response needs to be send in that case.
   # See: https://github.com/ethereum/devp2p/blob/master/discv5/discv5-wire.md#talkreq-request-0x05
-  let messageResponse = talkresp
-    .flatMap(proc (x: seq[byte]): Result[Message, cstring] = decodeMessage(x))
-    .flatMap(proc (m: Message): Result[Response, cstring] =
+
+  let messageResponse = talkresp.mapErr(proc (x: cstring): string = $x)
+    .flatMap(proc (x: seq[byte]): Result[Message, string] = decodeMessage(x))
+    .flatMap(proc (m: Message): Result[Response, string] =
       getInnerMessage[Response](m))
 
   if messageResponse.isOk():