Subscribe to new blocks

ethers/provider.nim

@@ -18,6 +18,7 @@ type
     data*: seq[byte]
     topics*: seq[Topic]
   LogHandler* = proc(log: Log) {.gcsafe, upraises:[].}
+  BlockHandler* = proc(blck: Block) {.gcsafe, upraises:[].}
   Topic* = array[32, byte]
   Block* = object
     number*: UInt256
@@ -57,5 +58,10 @@ method subscribe*(provider: Provider,
                  Future[Subscription] {.base.} =
   doAssert false, "not implemented"
 
+method subscribe*(provider: Provider,
+                  callback: BlockHandler):
+                 Future[Subscription] {.base.} =
+  doAssert false, "not implemented"
+
 method unsubscribe*(subscription: Subscription) {.base, async.} =
   doAssert false, "not implemented"

ethers/providers/jsonrpc.nim

@@ -127,21 +127,34 @@ method getChainId*(provider: JsonRpcProvider): Future[UInt256] {.async.} =
   except CatchableError:
     return parse(await client.net_version(), UInt256)
 
+proc subscribe(provider: JsonRpcProvider,
+               name: string,
+               filter: ?Filter,
+               handler: SubscriptionHandler): Future[Subscription] {.async.} =
+  let client = await provider.client
+  doAssert client of RpcWebSocketClient, "subscriptions require websockets"
+
+  let id = await client.eth_subscribe(name, filter)
+  provider.subscriptions[id] = handler
+
+  return JsonRpcSubscription(id: id, provider: provider)
+
 method subscribe*(provider: JsonRpcProvider,
                   filter: Filter,
                   callback: LogHandler):
                  Future[Subscription] {.async.} =
-  let client = await provider.client
-  doAssert client of RpcWebSocketClient, "subscriptions require websockets"
-
   proc handler(id, arguments: JsonNode) =
     if log =? Log.fromJson(arguments["result"]).catch:
       callback(log)
+  return await provider.subscribe("logs", filter.some, handler)
 
-  let id = await client.eth_subscribe("logs", some filter)
-  provider.subscriptions[id] = handler
-
-  return JsonRpcSubscription(id: id, provider: provider)
+method subscribe*(provider: JsonRpcProvider,
+                  callback: BlockHandler):
+                 Future[Subscription] {.async.} =
+  proc handler(id, arguments: JsonNode) =
+    if blck =? Block.fromJson(arguments["result"]).catch:
+      callback(blck)
+  return await provider.subscribe("newHeads", Filter.none, handler)
 
 method unsubscribe*(subscription: JsonRpcSubscription) {.async.} =
   let provider = subscription.provider

ethers/providers/jsonrpc/signatures.nim

@@ -9,5 +9,5 @@ proc eth_estimateGas(transaction: Transaction): UInt256
 proc eth_chainId(): UInt256
 proc eth_sendTransaction(transaction: Transaction): array[32, byte]
 proc eth_sign(account: Address, message: seq[byte]): seq[byte]
-proc eth_subscribe(name: string, filter: ?Filter): JsonNode
+proc eth_subscribe(name: string, filter = Filter.none): JsonNode
 proc eth_unsubscribe(id: JsonNode): bool

testmodule/testJsonRpcProvider.nim

@@ -39,3 +39,14 @@ suite "JsonRpcProvider":
     check block1.hash != block2.hash
     check block1.number < block2.number
     check block1.timestamp < block2.timestamp
+
+  test "subscribes to new blocks":
+    let oldBlock = !await provider.getBlock(BlockTag.latest)
+    var newBlock: Block
+    let blockHandler = proc(blck: Block) = newBlock = blck
+    let subscription = await provider.subscribe(blockHandler)
+    discard await provider.send("evm_mine")
+    check newBlock.number > oldBlock.number
+    check newBlock.timestamp > oldBlock.timestamp
+    check newBlock.hash != oldBlock.hash
+    await subscription.unsubscribe()