There should be a warning if we know that a Safe tx will fail

What is this feature about? (1 sentence)

This will display a warning in case the Safe knows that a tx will (most likely) fail.

Why is it needed? What is the value? For whom do we build it?

• If we know already, that a tx will fail, then we could save users gas costs.
• When executing transactions via MetaMask that will revert, MetaMask warns you before you execute the transaction. An easy example is trying to transfer more ERC20 tokens than the account holds to someone else.
• Because of implementation details the execution transaction for a Safe transaction will not fail, therefore MetaMask cannot warn you.

High-level overview of the feature

• Please check before submitting the execution transaction to the wallet if execTransactionreturns true.
• In case there will be an error, display that to the user. Something like “This transaction will most likely fail.”
• Note 1: This is only possible for the executor, i.e. when all signatures are present.
• Note 2: It should still be possible for the user to submit the tx. There are cases, where estimation is not possible
• Note 3: Please don’t implement the new signing flow design as part of this ticket. That should be done separate.

Misc

This is how Metamask displays this:

Updates

• Sep 30, Tobi: Add more context to this.

[rmeissner]

Hey @Agupane sorry for the late reply. So the simplest way I see right now using existing code is that you call the estimateSafeTxGas method and check if the returned value is 0. This method should only return 0 if we cannot estimate the transaction which means that it will most likely fail.

Even if this method returns 0 because something else fails, we should warn the user, as using 0 for safeTxGas requires special attention (since you need to adjust the gas value manually)

[Agupane]

Hey @rmeissner we have a question about the feature:

Before we ask for the user’s signature we called execTransaction with the arguments of the ReviewTransaction modal

await safeInstance.methods
      .execTransaction(...args)
      .call()

And this returns the following error:

{
  "originalError": {
    "code": 3,
    "data": "0x08c379a00000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000001a4861736820686173206e6f74206265656e20617070726f766564000000000000",
    "message": "execution reverted: Hash has not been approved"
  }
}

Are we doing something wrong? do you have any ideas about how we should verify if the tx will fail or not

cc: @nicosampler