Custom token transfers don't work based on the order of account updates.

[berzanorg]

There was no issue when I was using o1js v0.17.0, but after I updated my project to v1.1.0 it started to throw the error below.

Error: Cannot push to an immutable forest

This code works: (fixed version)

const mintTx = await Mina.transaction(userAccount2, async () => {
    AccountUpdate.fundNewAccount(userAccount2)
    token.transfer(userAccount2, userAccount1, UInt64.from(1000))
})

But this doesn't work: (old version)

const mintTx = await Mina.transaction(userAccount2, async () => {
    token.transfer(userAccount2, userAccount1, UInt64.from(1000))
    AccountUpdate.fundNewAccount(userAccount2)
})

And throws this error, Error: Cannot push to an immutable forest.

You can replicate the same error just by using a basic custom token contract like below:

export class TokenContract extends BaseTokenContract {
    @method async mint(amount: UInt64, receiver: PublicKey) {
        this.internal.mint({
            address: receiver,
            amount,
        })
    }

    @method async approveBase(forest: AccountUpdateForest) {
        this.checkZeroBalanceChange(forest)
    }
}

Maybe having a more clear error message would make it easier to debug. Or if it is possible, making both of the snippets work like in the previous versions would be very good.

[mitschabaude]

@berzanorg you're just missing an await:

const mintTx = await Mina.transaction(userAccount2, async () => {
-  token.transfer(userAccount2, userAccount1, UInt64.from(1000))
+  await token.transfer(userAccount2, userAccount1, UInt64.from(1000))
   AccountUpdate.fundNewAccount(userAccount2)
})

[mitschabaude]

It seems hard to give consistently good error messages for this problem :/

Here's what happens:

• Missing the await just means that the fundNewAccount() call happens while we are still within the context of the transfer() call
• So, AccountUpdate.fundNewAccount() creates an account update and tries to push it as a child update of the transfer() call
• However, transfer() fully "finalizes" its forest of child account updates, so adding another child creates an error
  • This finalizing happens as follows:
    • transfer() creates an AccountUpdateForest, and passes it to the internal approveBase()
    • your approveBase() internally calls TokenContract.forEachUpdate() which calls this.approve(forest), which makes the input forest be the final account update layout of this method call