feat: decoding candidates for unverified contracts

[zachdaniel]

Motivation

• In order to show what function we suspect was called, we need to store and then list any potential contract ABI matches from other verified smart contracts. This will give users as much information as possible about unverified contract.

Changelog

Enhancements

• Store any new method identifiers we receive.
• List them as possibilities on transactions for unverified transactions.

[coveralls]

Pull Request Test Coverage Report for Build dcfff138-763e-440b-aea1-904ae556fca1

• 19 of 32 (59.38%) changed or added relevant lines in 4 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 84.506%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
apps/explorer/test/support/factory.ex	1	2	50.0%
apps/explorer/lib/explorer/chain/contract_method.ex	12	15	80.0%
apps/explorer/lib/explorer/chain/transaction.ex	2	6	33.33%
apps/explorer/lib/explorer/chain/smart_contract.ex	4	9	44.44%

Files with Coverage Reduction	New Missed Lines	%
apps/indexer/lib/indexer/block/catchup/fetcher.ex	2	66.67%

Totals
Change from base Build 1cdb12bf-a042-4b41-9afc-47bd5e6bef67:	0.0%
Covered Lines:	4276
Relevant Lines:	5060

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💛 - Coveralls

[acravenho]

I'm not able to get this to work correctly. I deployed and verified a simple token here: https://blockscout.com/poa/core/address/0x8deb2e426835067f48ac034958cdd9daa38bd0a2/contracts

If you want to replicate this locally the only thing extra you might need is the constructor arguments:

00000000000000000000000057da3f24d81186b344649fe92b120ad45100d749

This contract has a simple function

{"name": "transfer", "type": "function", "inputs": [{"name": "_to", "type": "address"}, {"name": "_value", "type": "uint256"}], "outputs": [{"name": "", "type": "bool"}], "payable": false, "constant": false, "stateMutability": "nonpayable"}

which is used by most other token transfers. They have the same 4byte signature.

I viewed a transaction with the same 4byte signature but there was no decoding of this input.

0x9f6079797ff552b661944d2fbaaa7b394b872b6d06254810a8fe2667e2e833e8

[acravenho]

It also used an identifier of -145924998. I'm not sure where this comes from.

[zachdaniel]

I'll take a look now.

[zachdaniel]

The error can be shown just w/in the ex_abi library in a console like so:

selector = %ABI.FunctionSelector{
  function: "transfer",
  input_names: ["_to", "_value"],
  inputs_indexed: nil,
  method_id: <<169, 5, 156, 187>>,
  returns: [:bool],
  type: :function,
  types: [:address, {:uint, 256}]
}

input = <<159, 96, 121, 121, 127, 245, 82, 182, 97, 148, 77, 47, 186, 170, 123, 57, 75, 135, 43, 109, 6, 37, 72, 16, 168, 254, 38, 103, 226, 232, 51, 232>>

ABI.decode(selector, input)

@ayrat555 would you mind taking a look also if you get the chance?

[acravenho]

After playing with some contracts, I think it looks really good. The only change I would request is the danger to info for unverified contracts.

[vbaranov]

Looks goot to me. Just some minor UI suggestions:

But I do not insist on these UI changes. There is more important, that functionality works. I've tested it with some ERC20, ERC721 smart-contracts

[vbaranov]

But I do not insist on these UI changes.

Oh, as I see we already use this UI for displaying of decoded inputs for verified contracts. Thus, forget my comment about UI 😃.