Polkaswap test task for Soramitsu

This project is based on substrate-node-template and contains a pallet implementing functionality resembling ERC20 smart contract.

The pallet implementation is located in pallets/erc20

Feature mapping

The mapping of ERC20 functions are as follows:

• name, symbol and decimals are available as metadata entries of the pallet
• totalSupply, balanceOf and allowance are available as storage getters
• transfer, approve and transferFrom are implemented as dispatchable functions
• _mint and _burn are implemented as public, but non-dispatchable functions and can be run only with other pallets

Instead of returning bools like the original functions, I decided to return rust errors, which is the way to go for dispatchable functions.

Otherwise, I believe, the implementation matches closely what happens in ERC20

Even though it was allowed, I did not use pallet-balances, as its concepts do not seem to match to what ERC20 expects (with stuff like locked funds). Also, it allowed me to expose nice storage getters.

Testing

I wrote some amount of unit tests for the pallet (can be found pallets/erc20/tests.rs).

Test cases include basic ones (using functions as intended) along with all possible error conditions and (some) corner-cases.

Documentation

There are doc-strings for all public items exposed from the pallet