Unable to transfer contract balance to another account

[LaurentTrk]

Hi,

The env.transfer() seems not doing its job in my environment. The balance is not changed, neither in the contract nor in the destination account. No exception/panic is raised.

I use it in a Ink contract, with something like :

let value = self.env().balance();
let _ = self.env().transfer(self.charity_pot, value);

Note : In the same contract, using the same charity_pot account, the env.terminate_contract() is correctly transferring the funds to the given account.

Please let me know if you need additionnal informations. Thanks for your help !

Environment

Using nightly-2020-08-23 and cargo-contract 0.7.0 on Ubuntu 20.04.

[dependencies]
ink_primitives = { version = "3.0.0-rc1", default-features = false }
ink_metadata = { version = "3.0.0-rc1", default-features = false, features = ["derive"], optional = true }
ink_env = { version = "3.0.0-rc1", default-features = false }
ink_storage = { version = "3.0.0-rc1", default-features = false }
ink_lang = { version = "3.0.0-rc1", default-features = false }

scale = { package = "parity-scale-codec", version = "1.3", default-features = false, features = ["derive"] }
scale-info = { version = "0.4", default-features = false, features = ["derive"], optional = true }

[Robbepop]

Thanks for the issue report!
I will look on the ink! side and @athei might take a look on the contracts-pallet side.
More information is always welcome. Can you maybe post your smart contract fully so that we can reproduce?
Did you try this on the Canvas test chain or locally?

[LaurentTrk]

Hi @Robbepop !
I run a local node.
You can find the whole contract here : https://github.com/LaurentTrk/hello-world-by-polkadot/blob/CharityRaffle/frame-development/charity-raffle
(that's my work in progress for the Hello World! hackathon ;) )

[Robbepop]

You should definitely update your ink! version to 3.0.0-rc2. But this will probably not fix this particular bug for you.

[LaurentTrk]

Done. And you are right, the bug is not fixed ;)

[athei]

I can't see any transfer call in your contract. Can you link the line which is not working? Also transfer won't panic but returns a recoverable error. The ink! doc is wrong about the panic. So make sure to not drop the Result on the floor (the compiler should give a warning if you do).

[LaurentTrk]

Argh, my bad, I sent you the working version with env.terminate_contract()... Sorry for that ;)

The result.Error is BelowSubsistenceThreshold which make sense if I transferred all the balance.
Before opening the issue, I tried keeping the env.minimum_balance() into the contract balance, without success...
I guess I misunderstanding the minimum balance meaning 🙄

Well, I changed the code logic to only transfer the amount transferred (leaving the endowment in the contract balance) and it works, the funds are correctly transferred 😃

So no problem. But maybe we can add some documentation about the transfer and the minimum balance ?

Btw, is there any way to return the Result<Ok or Err> to the caller ? I return some custom Errors in my contract for logic errors, but the extrinsic always succeed... Thanks for your help.

[cmichi]

Btw, is there any way to return the Result to the caller ? I return some custom Errors in my contract for logic errors, but the extrinsic always succeed...

@LaurentTrk Unfortunately we don't have error forwarding yet, it's on the roadmap though!

[LaurentTrk]

Thanks @cmichi for your answer and the docs improvement !

By any chance, do you have any tip on how to mock transferred_balance() when unit testing payable transactions ? Maybe we should add it in the samples as well...

[cmichi]

@LaurentTrk Here's an example: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=871521ec0b23f6fb0c4facd1cc5ca420. Make sure to read the comment at the bottom, mocking is the only possibility at the moment, we hope to improve this in the future.