Replace eth_getBlockReceipts return type with Opt[T] instead of Optio… (#131)

* Replace eth_getBlockReceipts return type with Opt[T] instead of Option[T]

reason:
Option[T] failed to compile when using nim v2
it is related to ref object. But also hard to reproduce outside
combination of nim-json-serialization + nim-json-rpc + something

* Add note about nim v2 regression

* Add test case of eth_getBlockReceipts usage

tests/helpers/handlers.nim

@@ -81,16 +81,10 @@ proc installHandlers*(server: RpcServer) =
     if x != "-1".JsonString:
       result = decodeFromString(x, Quantity)
 
-  when NimMajor >= 2:
-    server.rpc("eth_getBlockReceipts") do(x: JsonString, blockId: RtBlockIdentifier) -> JsonString:
-      # TODO: cannot prove obj is not nil
-      let jsonBytes = JrpcConv.decode(x.string, string)
-      return jsonBytes.JsonString
-  else:
-    server.rpc("eth_getBlockReceipts") do(x: JsonString, blockId: RtBlockIdentifier) -> Option[seq[ReceiptObject]]:
-      if x != "-1".JsonString:
-        let r = decodeFromString(x, Option[seq[ReceiptObject]])
-        return r
+  server.rpc("eth_getBlockReceipts") do(x: JsonString, blockId: RtBlockIdentifier) -> Opt[seq[ReceiptObject]]:
+    if x != "-1".JsonString:
+      let r = decodeFromString(x, Opt[seq[ReceiptObject]])
+      return r
 
   server.rpc("eth_getBlockByNumber") do(x: JsonString, blockId: RtBlockIdentifier, fullTransactions: bool) -> BlockObject:
     var blk: BlockObject

tests/test_execution_api.nim

@@ -5,7 +5,9 @@ import
   json_rpc/[rpcclient, rpcserver],
   json_rpc/private/jrpc_sys,
   ../web3/conversions,
-  ./helpers/handlers
+  ./helpers/handlers,
+  ../web3/eth_api,
+  results
 
 type
   TestData = tuple
@@ -109,3 +111,23 @@ suite "Ethereum execution api":
 
   waitFor srv.stop()
   waitFor srv.closeWait()
+
+proc setupMethods(server: RpcServer) =
+  server.rpc("eth_getBlockReceipts") do(blockId: RtBlockIdentifier) -> Opt[seq[ReceiptObject]]:
+    var res: seq[ReceiptObject]
+    return Opt.some(res)
+
+suite "Test eth api":
+  var srv = newRpcHttpServer(["127.0.0.1:0"])
+  srv.setupMethods()
+  srv.start()
+
+  test "eth_getBlockReceipts generic functions":
+    let client = newRpcHttpClient()
+    waitFor client.connect("http://" & $srv.localAddress()[0])
+    let res = waitFor client.eth_getBlockReceipts(blockId("latest"))
+    check res.isSome
+    waitFor client.close()
+
+  waitFor srv.stop()
+  waitFor srv.closeWait()

web3/conversions.nim

@@ -14,6 +14,7 @@ import
   faststreams/textio,
   json_rpc/jsonmarshal,
   json_serialization/std/options,
+  json_serialization/stew/results,
   json_serialization,
   ./primitives,
   ./engine_api_types,
@@ -364,6 +365,26 @@ proc writeValue*(w: var JsonWriter[JrpcConv], v: SyncingStatus)
   else:
     w.writeValue(v.syncObject)
 
+# Somehow nim2 refuse to generate automatically
+proc readValue*(r: var JsonReader[JrpcConv], val: var Opt[seq[ReceiptObject]])
+       {.gcsafe, raises: [IOError, SerializationError].} =
+  mixin readValue
+
+  if r.tokKind == JsonValueKind.Null:
+    reset val
+    r.parseNull()
+  else:
+    val.ok r.readValue(seq[ReceiptObject])
+
+proc writeValue*(w: var JsonWriter[JrpcConv], v: Opt[seq[ReceiptObject]])
+      {.gcsafe, raises: [IOError].} =
+  mixin writeValue
+
+  if v.isOk:
+    w.writeValue v.get
+  else:
+    w.writeValue JsonString("null")
+
 func `$`*(v: Quantity): string {.inline.} =
   encodeQuantity(v.uint64)
 

web3/eth_api.nim

@@ -11,6 +11,7 @@
 import
   std/[json, options],
   json_serialization/std/[options],
+  json_serialization/stew/results,
   json_rpc/[client, jsonmarshal],
   stint,
   ./conversions,
@@ -39,7 +40,17 @@ createRpcSigsFromNim(RpcClient):
   proc eth_getTransactionCount(data: Address, blockId: BlockIdentifier): Quantity
   proc eth_getBlockTransactionCountByHash(data: BlockHash): Quantity
   proc eth_getBlockTransactionCountByNumber(blockId: BlockIdentifier): Quantity
-  proc eth_getBlockReceipts(blockId: BlockIdentifier): Option[seq[ReceiptObject]]
+
+  # TODO: Investigate why nim v2 cannot instantiate generic functions
+  # with oneof params `blockId: BlockIdentifier` and and return type
+  # Opt[seq[ReceiptObject]], this is a regression after all
+  when false:
+    proc eth_getBlockReceipts(blockId: BlockIdentifier): Opt[seq[ReceiptObject]]
+
+  proc eth_getBlockReceipts(blockId: string): Opt[seq[ReceiptObject]]
+  proc eth_getBlockReceipts(blockId: BlockNumber): Opt[seq[ReceiptObject]]
+  proc eth_getBlockReceipts(blockId: RtBlockIdentifier): Opt[seq[ReceiptObject]]
+
   proc eth_getUncleCountByBlockHash(data: BlockHash): Quantity
   proc eth_getUncleCountByBlockNumber(blockId: BlockIdentifier): Quantity
   proc eth_getCode(data: Address, blockId: BlockIdentifier): seq[byte]