feat: Allow contract transactions to be waited on

Allow waiting for a specified number of confirmations for contract transactions.

This change only requires an optional TransactionResponse return type to be added to the contract function. This allows the transaction hash to be passed to `.wait`.

For example, previously the `mint` method looked like this without a return value:
```
method mint(token: TestToken, holder: Address, amount: UInt256) {.base, contract.}
```
it still works without a return value, but if we want to wait for a 3 confirmations, we can now define it like this:
```
method mint(token: TestToken, holder: Address, amount: UInt256): ?TransactionResponse {.base, contract.}
```
and use like this:
```
let receipt = await token.connect(signer0)
                    .mint(accounts[1], 100.u256)
                    .wait(3) # wait for 3 confirmations
```

ethers/contract.nim

@@ -101,6 +101,13 @@ func isConstant(procedure: NimNode): bool =
       return true
   false
 
+func isTxResponse(returntype: NimNode): bool =
+  return returntype.kind == nnkPrefix and
+    returntype[0].kind == nnkIdent and
+    returntype[0].strVal == "?" and
+    returntype[1].kind == nnkIdent and
+    returntype[1].strVal == $TransactionResponse
+
 func addContractCall(procedure: var NimNode) =
   let contract = procedure[3][1][0]
   let function = $basename(procedure[0])
@@ -114,9 +121,15 @@ func addContractCall(procedure: var NimNode) =
       else:
         quote:
           return await call(`contract`, `function`, `parameters`, `returntype`)
+    else:
+      # When ?TransactionResponse is specified as the return type of contract
+      # method, it allows for contract transactions to be awaited on
+      # confirmations
+      if returntype.isTxResponse:
+        quote:
+          return await send(`contract`, `function`, `parameters`)
       else:
         quote:
-        # TODO: need to be able to use wait here
           discard await send(`contract`, `function`, `parameters`)
 
 func addFuture(procedure: var NimNode) =
@@ -132,7 +145,14 @@ func addAsyncPragma(procedure: var NimNode) =
 
 func checkReturnType(procedure: NimNode) =
   let returntype = procedure[3][0]
-  if returntype.kind != nnkEmpty and not procedure.isConstant:
+
+  if returntype.kind != nnkEmpty:
+    # Do not throw exception for methods that have a TransactionResponse
+    # return type as that is needed for .wait
+    if returntype.isTxResponse:
+      return
+
+    if not procedure.isConstant:
       const message =
         "only contract functions with {.view.} or {.pure.} " &
         "can have a return type"

ethers/provider.nim

@@ -10,30 +10,22 @@ push: {.upraises: [].}
 
 type
   Provider* = ref object of RootObj
-
   Subscription* = ref object of RootObj
-
   Filter* = object
     address*: Address
     topics*: seq[Topic]
-
   Log* = object
     data*: seq[byte]
     topics*: seq[Topic]
-
   TransactionHash* = array[32, byte]
-
   BlockHash* = array[32, byte]
-
   TransactionStatus* = enum
     Failure = 0,
     Success = 1,
     Invalid = 2
-
   TransactionResponse* = object
     provider*: Provider
     hash*: TransactionHash
-
   TransactionReceipt* = object
     sender*: ?Address
     to*: ?Address
@@ -47,38 +39,17 @@ type
     blockNumber*: ?UInt256
     cumulativeGasUsed*: UInt256
     status*: TransactionStatus
-
-  ProviderEventKind* = enum
-    LogEvent,
-    NewHeadEvent
-
-  ProviderEvent* = object
-    case kind*: ProviderEventKind
-    of LogEvent:
-      log*: Log
-    of NewHeadEvent:
-      newHead*: NewHead
-
-  ProviderEventHandler* = proc(event: ProviderEvent) {.gcsafe, upraises:[].}
-
-  ProviderEventCallback* = (ProviderEventHandler, ProviderEventKind)
-
   LogHandler* = proc(log: Log) {.gcsafe, upraises:[].}
   BlockHandler* = proc(blck: Block) {.gcsafe, upraises:[].}
-
-  NewHead* = object
-    number*: UInt256 # block number
-    transactions*: seq[TransactionHash]
-  # NewHeadHandler* = EventHandler[NewHead]
-
   Topic* = array[32, byte]
-
   Block* = object
     number*: UInt256
     timestamp*: UInt256
     hash*: array[32, byte]
 
 const DEFAULT_CONFIRMATIONS* {.intdefine.} = 12
+const RECEIPT_TIMEOUT_BLKS* {.intdefine.} = 50 # in blocks
+const RECEIPT_POLLING_INTERVAL* {.intdefine.} = 1 # in seconds
 
 method getBlockNumber*(provider: Provider): Future[UInt256] {.base.} =
   doAssert false, "not implemented"

ethers/providers/jsonrpc.nim

@@ -198,7 +198,7 @@ method sendTransaction*(signer: JsonRpcSigner,
 
 method wait*(tx: TransactionResponse,
              wantedConfirms = DEFAULT_CONFIRMATIONS,
-             timeoutInBlocks = int.none): # will error if tx not mined in x blocks
+             timeoutInBlocks = RECEIPT_TIMEOUT_BLKS.some): # will error if tx not mined in x blocks
             Future[TransactionReceipt]
             {.async, upraises: [JsonRpcProviderError].} = # raises for clarity
 
@@ -239,8 +239,7 @@ method wait*(tx: TransactionResponse,
         raiseProviderError("Transaction was not mined in " &
           $(!timeoutInBlocks) & " blocks")
 
-    # TODO: should this be set to the current block time?
-    await sleepAsync(1.seconds)
+    await sleepAsync(RECEIPT_POLLING_INTERVAL.seconds)
 
   # has been mined, need to check # of confirmations thus far
   let confirms = (!receipt).confirmations(startBlock)
@@ -254,7 +253,7 @@ method wait*(tx: TransactionResponse,
 
 method wait*(tx: Future[TransactionResponse],
              wantedConfirms = DEFAULT_CONFIRMATIONS,
-             timeoutInBlocks = int.none):
+             timeoutInBlocks = RECEIPT_TIMEOUT_BLKS.some):
             Future[TransactionReceipt] {.async.} =
   ## Convenience method that allows wait to be chained to a sendTransaction
   ## call, eg:
@@ -262,3 +261,19 @@ method wait*(tx: Future[TransactionResponse],
 
   let txResp = await tx
   return await txResp.wait(wantedConfirms, timeoutInBlocks)
+
+method wait*(tx: Future[?TransactionResponse],
+             wantedConfirms = DEFAULT_CONFIRMATIONS,
+             timeoutInBlocks = RECEIPT_TIMEOUT_BLKS.some):
+            Future[TransactionReceipt] {.async.} =
+  ## Convenience method that allows wait to be chained to a contract
+  ## transaction, eg:
+  ## `await token.connect(signer0)
+  ##          .mint(accounts[1], 100.u256)
+  ##          .wait(3)`
+
+  let txResp = await tx
+  if txResp.isNone:
+    raiseProviderError("Transaction hash required. Possibly was a call instead of a send?")
+
+  return await (!txResp).wait(wantedConfirms, timeoutInBlocks)

testmodule/miner.nim

@@ -0,0 +1,8 @@
+import chronos
+import pkg/ethers/providers/jsonrpc
+
+
+proc mineBlocks*(provider: JsonRpcProvider, blks: int) {.async.} =
+  for i in 1..blks:
+    discard await provider.send("evm_mine")
+    await sleepAsync(1.seconds)

testmodule/testContracts.nim

@@ -3,6 +3,7 @@ import pkg/asynctest
 import pkg/stint
 import pkg/ethers
 import ./hardhat
+import ./miner
 
 type
 
@@ -18,8 +19,7 @@ method totalSupply*(erc20: Erc20): UInt256 {.base, contract, view.}
 method balanceOf*(erc20: Erc20, account: Address): UInt256 {.base, contract, view.}
 method allowance*(erc20: Erc20, owner, spender: Address): UInt256 {.base, contract, view.}
 method transfer*(erc20: Erc20, recipient: Address, amount: UInt256) {.base, contract.}
-
-method mint(token: TestToken, holder: Address, amount: UInt256) {.base, contract.}
+method mint(token: TestToken, holder: Address, amount: UInt256): ?TransactionResponse {.base, contract.}
 
 suite "Contracts":
 
@@ -45,12 +45,12 @@ suite "Contracts":
 
   test "can call non-constant functions":
     token = TestToken.new(token.address, provider.getSigner())
-    await token.mint(accounts[1], 100.u256)
+    discard await token.mint(accounts[1], 100.u256)
     check (await token.totalSupply()) == 100.u256
     check (await token.balanceOf(accounts[1])) == 100.u256
 
   test "can call non-constant functions without a signer":
-    await token.mint(accounts[1], 100.u256)
+    discard await token.mint(accounts[1], 100.u256)
     check (await token.balanceOf(accounts[1])) == 0.u256
 
   test "can call constant functions without a return type":
@@ -77,7 +77,7 @@ suite "Contracts":
   test "can connect to different providers and signers":
     let signer0 = provider.getSigner(accounts[0])
     let signer1 = provider.getSigner(accounts[1])
-    await token.connect(signer0).mint(accounts[0], 100.u256)
+    discard await token.connect(signer0).mint(accounts[0], 100.u256)
     await token.connect(signer0).transfer(accounts[1], 50.u256)
     await token.connect(signer1).transfer(accounts[2], 25.u256)
     check (await token.connect(provider).balanceOf(accounts[0])) == 50.u256
@@ -94,7 +94,7 @@ suite "Contracts":
     let signer1 = provider.getSigner(accounts[1])
 
     let subscription = await token.subscribe(Transfer, handleTransfer)
-    await token.connect(signer0).mint(accounts[0], 100.u256)
+    discard await token.connect(signer0).mint(accounts[0], 100.u256)
     await token.connect(signer0).transfer(accounts[1], 50.u256)
     await token.connect(signer1).transfer(accounts[2], 25.u256)
     await subscription.unsubscribe()
@@ -114,9 +114,22 @@ suite "Contracts":
     let signer0 = provider.getSigner(accounts[0])
 
     let subscription = await token.subscribe(Transfer, handleTransfer)
-    await token.connect(signer0).mint(accounts[0], 100.u256)
+    discard await token.connect(signer0).mint(accounts[0], 100.u256)
     await subscription.unsubscribe()
 
     await token.connect(signer0).transfer(accounts[1], 50.u256)
 
     check transfers == @[Transfer(receiver: accounts[0], value: 100.u256)]
+
+  test "can wait for contract interaction tx to be mined":
+    # must be spawned so we can get newHeads inside of .wait
+    asyncSpawn provider.mineBlocks(3)
+
+    let signer0 = provider.getSigner(accounts[0])
+    let receipt = await token.connect(signer0)
+                    .mint(accounts[1], 100.u256)
+                    .wait(3) # wait for 3 confirmations
+    let endBlock = await provider.getBlockNumber()
+
+    check receipt.blockNumber.isSome # was eventually mined
+    check (endBlock - !receipt.blockNumber) + 1 == 3 # +1 for the block the tx was mined in

testmodule/testJsonRpcProvider.nim

@@ -1,7 +1,7 @@
 import std/json
 import pkg/asynctest
 import pkg/chronos
-import pkg/ethers #/providers/jsonrpc
+import pkg/ethers
 import pkg/stew/byteutils
 import ./examples
 import ./miner