Exception handling signatures (#97)

Minimally work around leaking `Exception` for
https://github.com/status-im/nim-chronos/pull/166

json_rpc/client.nim

@@ -10,11 +10,12 @@ export
 
 type
   ClientId* = int64
+  MethodHandler* = proc (j: JsonNode) {.gcsafe, raises: [Defect, CatchableError].}
   RpcClient* = ref object of RootRef
     awaiting*: Table[ClientId, Future[Response]]
     lastId: ClientId
-    methodHandlers: Table[string, proc(j: JsonNode) {.gcsafe.}]
-    onDisconnect*: proc() {.gcsafe.}
+    methodHandlers: Table[string, MethodHandler]
+    onDisconnect*: proc() {.gcsafe, raises: [Defect].}
 
   Response* = JsonNode
 
@@ -26,10 +27,13 @@ proc rpcCallNode*(path: string, params: JsonNode, id: ClientId): JsonNode =
   %{"jsonrpc": %"2.0", "method": %path, "params": params, "id": %id}
 
 method call*(client: RpcClient, name: string,
-             params: JsonNode): Future[Response] {.gcsafe, async, base.} =
+             params: JsonNode): Future[Response] {.
+    base, async, gcsafe, raises: [Defect, CatchableError].} =
   discard
 
-method close*(client: RpcClient) {.base, gcsafe, async.} = discard
+method close*(client: RpcClient): Future[void] {.
+    base, async, gcsafe, raises: [Defect, CatchableError].} =
+  discard
 
 template `or`(a: JsonNode, b: typed): JsonNode =
   if a == nil: b else: a
@@ -37,7 +41,10 @@ template `or`(a: JsonNode, b: typed): JsonNode =
 proc processMessage*(self: RpcClient, line: string) =
   # Note: this doesn't use any transport code so doesn't need to be
   # differentiated.
-  let node = parseJson(line)
+  let node = try: parseJson(line)
+  except CatchableError as exc: raise exc
+  # TODO https://github.com/status-im/nimbus-eth2/issues/2430
+  except Exception as exc: raise (ref ValueError)(msg: exc.msg, parent: exc)
 
   if "id" in node:
     let id = node{"id"} or newJNull()
@@ -164,7 +171,7 @@ proc processRpcSigs(clientType, parsedCode: NimNode): NimNode =
       var procDef = createRpcFromSig(clientType, line)
       result.add(procDef)
 
-proc setMethodHandler*(cl: RpcClient, name: string, callback: proc(j: JsonNode) {.gcsafe.}) =
+proc setMethodHandler*(cl: RpcClient, name: string, callback: MethodHandler) =
   cl.methodHandlers[name] = callback
 
 proc delMethodHandler*(cl: RpcClient, name: string) =

json_rpc/clients/httpclient.nim

@@ -170,7 +170,8 @@ proc httpMethod*(client: RpcHttpClient, m: HttpMethod) =
   client.options.httpMethod = m
 
 method call*(client: RpcHttpClient, name: string,
-             params: JsonNode): Future[Response] {.async, gcsafe.} =
+             params: JsonNode): Future[Response] {.
+    async, gcsafe, raises: [Defect, CatchableError].} =
   ## Remotely calls the specified RPC method.
   let id = client.getNextId()
 

json_rpc/clients/socketclient.nim

@@ -18,7 +18,8 @@ proc newRpcSocketClient*: RpcSocketClient =
   RpcSocketClient.new()
 
 method call*(self: RpcSocketClient, name: string,
-             params: JsonNode): Future[Response] {.async.} =
+             params: JsonNode): Future[Response] {.
+    async, gcsafe, raises: [Defect, CatchableError].} =
   ## Remotely calls the specified RPC method.
   let id = self.getNextId()
   var value = $rpcCallNode(name, params, id) & "\r\n"

json_rpc/clients/websocketclient.nim

@@ -19,7 +19,8 @@ proc newRpcWebSocketClient*: RpcWebSocketClient =
   RpcWebSocketClient.new()
 
 method call*(self: RpcWebSocketClient, name: string,
-             params: JsonNode): Future[Response] {.async.} =
+             params: JsonNode): Future[Response] {.
+    async, gcsafe, raises: [Defect, CatchableError].} =
   ## Remotely calls the specified RPC method.
   let id = self.getNextId()
   var value = $rpcCallNode(name, params, id) & "\r\n"

json_rpc/router.nim

@@ -10,7 +10,7 @@ type
   StringOfJson* = JsonString
 
   # Procedure signature accepted as an RPC call by server
-  RpcProc* = proc(input: JsonNode): Future[StringOfJson] {.gcsafe.}
+  RpcProc* = proc(input: JsonNode): Future[StringOfJson] {.gcsafe, raises: [Defect, CatchableError].}
 
   RpcRouter* = object
     procs*: Table[string, RpcProc]
@@ -90,6 +90,9 @@ proc route*(router: RpcRouter, data: string): Future[string] {.async, gcsafe.} =
     try: parseJson(data)
     except CatchableError as err:
       return string(wrapError(JSON_PARSE_ERROR, err.msg))
+    except Exception as err:
+      # TODO https://github.com/status-im/nimbus-eth2/issues/2430
+      return string(wrapError(JSON_PARSE_ERROR, err.msg))
 
   return string(await router.route(node))