internal/ethapi: set necessary fee price before gas estimation

[txhsl]

Close #262.

[txhsl]

By filling up the MaxPriorityFeePerGas field, we can let third-party tools to pass minGasTipCap check if they don't provide it.

But, let me take Remix as an example, it only provides a MaxFeePerGas which equals 4/3 of the latest base fee. Since we are going to burn 50% or less of the transaction fee, the MaxFeePerGas should be larger than 2 * baseFee, otherwise the sanity check will fail. So the issue is not fully solved yet.

Is it correct to overwrite the MaxFeePerGas in estimation, or any other solutions?

[AnnaShaleva]

Is it correct to overwrite the MaxFeePerGas in estimation, or any other solutions?

We may try to modify args.setFeeDefaults in order to make special conditions for NeoXBurn hardfork. But I'm not sure if MaxFeePerGas is safe to be modified, even only in case if it's insufficient. Because other tools may rely on their value, whereas backend silently modifies it for its own check, and if it's not a problem with Remix, then it may be a problem for some other tool.

[txhsl]

But I'm not sure if MaxFeePerGas is safe to be modified, even only in case if it's insufficient. Because other tools may rely on their value, whereas backend silently modifies it for its own check, and if it's not a problem with Remix, then it may be a problem for some other tool.

Well, let's have a look at documents.

The code comment says.

EstimateGas returns the lowest possible gas limit that allows the transaction to run successfully at block blockNrOrHash, or the latest block if blockNrOrHash is unspecified. It returns error if the transaction would revert or if there are unexpected failures. The returned value is capped by both args.Gas (if non-nil & non-zero) and the backend's RPCGasCap configuration (if non-zero).

The official document says.

EstimateGas generates and returns an estimate of how much gas is necessary to allow the transaction to complete. The transaction will not be added to the blockchain.

And Alchemy notes.

• eth_estimateGas will check the balance of the sender (to make sure that the sender has enough gas to complete the request). This means that even though the call doesn't consume any gas, the from address must have enough gas to execute the transaction.
• If no gas is specified geth uses the block gas limit from the pending block as an upper bound. As a result, the returned estimate might not be enough to execute the call/transaction when the amount of actual gas needed is higher than the pending block gas limit.

So, there are several points.

1. EstimateGas returns a gas limit value if the requested tx can succeed;
2. EstimateGas returns an error if the requested tx failed;
3. EstimateGas checks the balance of the sender and returns an error if the balance is not enough to pay for the requested tx.

I think, set a minimum price for empty request is compatible based on this description. Ideally, we should return a ErrUnderpriced error to Remix, but we have to make it successful.

setFeeDefaults() works good on filling in default fee values for unspecified tx fields, but we are going to do something different, which is filling in minimum allowed fee values for underpriced tx. So I'm going to add a new one.

[AnnaShaleva]

This way looks better.