Fix: ensure that gas estimations are done using the "pending" block

ethers/signer.nim

@@ -88,7 +88,7 @@ method estimateGas*(
 
   transaction.sender = some(address)
   try:
-    return await signer.provider.estimateGas(transaction)
+    return await signer.provider.estimateGas(transaction, blockTag)
   except ProviderError as e:
     raiseEstimateGasError transaction, e
 
@@ -161,7 +161,7 @@ method populateTransaction*(
       # stuck transactions
       populated.nonce = some(await signer.getNonce())
       try:
-        populated.gasLimit = some(await signer.estimateGas(populated))
+        populated.gasLimit = some(await signer.estimateGas(populated, BlockTag.pending))
       except EstimateGasError as e:
         signer.decreaseNonce()
         raise e
@@ -173,7 +173,7 @@ method populateTransaction*(
       if transaction.nonce.isNone:
         populated.nonce = some(await signer.getNonce())
       if transaction.gasLimit.isNone:
-        populated.gasLimit = some(await signer.estimateGas(populated))
+        populated.gasLimit = some(await signer.estimateGas(populated, BlockTag.pending))
 
   finally:
     signer.populateLock.release()

testmodule/test.nim

@@ -6,5 +6,6 @@ import ./testEvents
 import ./testWallet
 import ./testTesting
 import ./testErc20
+import ./testGasEstimation
 
 {.warning[UnusedImport]:off.}

testmodule/testGasEstimation.nim

@@ -0,0 +1,41 @@
+import pkg/asynctest
+import pkg/ethers
+import pkg/serde
+import ./hardhat
+
+type
+  TestGasEstimation = ref object of Contract
+
+proc getTime(contract: TestGasEstimation): UInt256 {.contract, view.}
+proc checkTimeEquals(contract: TestGasEstimation, expected: UInt256) {.contract.}
+
+suite "gas estimation":
+
+  var contract: TestGasEstimation
+  var provider: JsonRpcProvider
+  var snapshot: JsonNode
+
+  setup:
+    provider = JsonRpcProvider.new()
+    snapshot = await provider.send("evm_snapshot")
+    let deployment = readDeployment()
+    let signer = provider.getSigner()
+    contract = TestGasEstimation.new(!deployment.address(TestGasEstimation), signer)
+
+  teardown:
+    discard await provider.send("evm_revert", @[snapshot])
+    await provider.close()
+
+  test "uses pending block for gas estimations":
+    let latest = CallOverrides(blockTag: some BlockTag.latest)
+    let pending = CallOverrides(blockTag: some BlockTag.pending)
+
+    # retrieve time of pending block
+    let time = await contract.getTime(overrides=pending)
+
+    # ensure that time of latest block and pending block differ
+    check (await contract.getTime(overrides=latest)) != time
+
+    # fails with "Transaction ran out of gas" when gas estimation
+    # is not done using the pending block
+    await contract.checkTimeEquals(time)

testnode/contracts/TestGasEstimation.sol

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+contract TestGasEstimation {
+
+  uint lastCheckedTime;
+
+  // this function returns a different value depending on whether
+  // it is called on the latest block, or on the pending block
+  function getTime() public view returns (uint) {
+    return block.timestamp;
+  }
+
+  // this function is designed to require a different amount of
+  // gas, depending on whether the parameter matches the block
+  // timestamp
+  function checkTimeEquals(uint expected) public {
+    if (expected == block.timestamp) {
+      lastCheckedTime = block.timestamp;
+    }
+  }
+}

testnode/deploy/testgasestimation.js

@@ -0,0 +1,6 @@
+module.exports = async ({ deployments, getNamedAccounts }) => {
+  const { deployer } = await getNamedAccounts();
+  await deployments.deploy("TestGasEstimation", { from: deployer });
+};
+
+module.exports.tags = ["TestGasEstimation"];