feat: cast decode can decode raw eip2718 txns

[ruvaag]

Motivation

Resolve #4752 and implement cast decode to decode raw EIP2718 transaction payloads

Solution

• Implement new clap subcommand Decode
• Implement SimpleCast::decode_tx that uses ethers_core::utils::rlp to decode raw eip2718 signed txns to ethers_core::types::transaction::eip2718::TypedTransaction and Signature
• Pretty print decoded txn details

[ruvaag]

@Evalir would really appreciate a review here. I think I'm close to getting this over the line and only struggling with the final step of the solution described above i.e. pretty-printing the decoded output.

This is what the current output looks using serde_json::to_string_pretty:

> cast decode 0x02f8f582a86a82058d8459682f008508351050808303fd84948e42f2f4101563bf679975178e880fd87d3efd4e80b884659ac74b00000000000000000000000080f0c1c49891dcfdd40b6e0f960f84e6042bcb6f000000000000000000000000b97ef9ef8734c71904d8002f8b6bc66dd9c48a6e00000000000000000000000000000000000000000000000000000000007ff4e20000000000000000000000000000000000000000000000000000000000000064c001a05d429597befe2835396206781b199122f2e8297327ed4a05483339e7a8b2022aa04c23a7f70fb29dda1b4ee342fb10a625e9b8ddc6a603fb4e170d4f6f37700cb8
Transaction: {
  "type": "0x02",
  "from": "0xddbfd6c43d6412b61dbbe463934b69f8c17d9430",
  "to": "0x8e42f2f4101563bf679975178e880fd87d3efd4e",
  "gas": "0x3fd84",
  "value": "0x0",
  "data": "0x659ac74b00000000000000000000000080f0c1c49891dcfdd40b6e0f960f84e6042bcb6f000000000000000000000000b97ef9ef8734c71904d8002f8b6bc66dd9c48a6e00000000000000000000000000000000000000000000000000000000007ff4e20000000000000000000000000000000000000000000000000000000000000064",
  "nonce": "0x58d",
  "accessList": [],
  "maxPriorityFeePerGas": "0x59682f00",
  "maxFeePerGas": "0x835105080"
}
Signature: {
  "r": "0x5d429597befe2835396206781b199122f2e8297327ed4a05483339e7a8b2022a",
  "s": "0x4c23a7f70fb29dda1b4ee342fb10a625e9b8ddc6a603fb4e170d4f6f37700cb8",
  "v": 1
}

ethers_core::types::transaction::eip2718::TypedTransaction doesn't implement fmt::Display so I'm not sure how best to print this out in the desired way. An alternative could be to pretty print thefmt::Debug outputs of TypedTransaction and Signature which would look something like this:

> cast decode 0x02f8f582a86a82058d8459682f008508351050808303fd84948e42f2f4101563bf679975178e880fd87d3efd4e80b884659ac74b00000000000000000000000080f0c1c49891dcfdd40b6e0f960f84e6042bcb6f000000000000000000000000b97ef9ef8734c71904d8002f8b6bc66dd9c48a6e00000000000000000000000000000000000000000000000000000000007ff4e20000000000000000000000000000000000000000000000000000000000000064c001a05d429597befe2835396206781b199122f2e8297327ed4a05483339e7a8b2022aa04c23a7f70fb29dda1b4ee342fb10a625e9b8ddc6a603fb4e170d4f6f37700cb8
Eip1559(
    Eip1559TransactionRequest {
        from: Some(
            0xddbfd6c43d6412b61dbbe463934b69f8c17d9430,
        ),
        to: Some(
            Address(
                0x8e42f2f4101563bf679975178e880fd87d3efd4e,
            ),
        ),
        gas: Some(
            261508,
        ),
        value: Some(
            0,
        ),
        data: Some(
            Bytes(0x659ac74b00000000000000000000000080f0c1c49891dcfdd40b6e0f960f84e6042bcb6f000000000000000000000000b97ef9ef8734c71904d8002f8b6bc66dd9c48a6e00000000000000000000000000000000000000000000000000000000007ff4e20000000000000000000000000000000000000000000000000000000000000064),
        ),
        nonce: Some(
            1421,
        ),
        access_list: AccessList(
            [],
        ),
        max_priority_fee_per_gas: Some(
            1500000000,
        ),
        max_fee_per_gas: Some(
            35250000000,
        ),
        chain_id: Some(
            43114,
        ),
    },
)
Signature {
    r: 42182739275790655586253530586324480569063940514059565326253468982835405783594,
    s: 34438775391995392764448454937167654498428095335712619789751606417593983831224,
    v: 1,
}

There's probably a third way - construct a custom template string which would replicate the desired format exactly, but I doubt if this is the best way to go since it tightly couples SimpleCast::decode_tx and TypedTransaction.

Any upstream modification of fields, new types of txns, and even potential migration of foundry away from ethers-rs itself would add an maintenance overhead. Additionally with three variants of the TypedTransaction Enum, each with multiple fields it would make the decode_tx function very bulky.

Curious to hear any thoughts and suggestions.

P.S - I'm aware the PR is missing proper comments, will add those before finalising it. Apologies if i'm missing something simple... only started with rust a few weeks back.

[mattsse]

a few nits

[mattsse]

thanks, last nit

[mattsse]

nit: both can be serialized into to_value and then merged like this:

fn merge(a: &mut Value, b: Value) {
    match (a, b) {
        (a @ &mut Value::Object(_), Value::Object(b)) => {
            let a = a.as_object_mut().unwrap();
            for (k, v) in b {
                merge(a.entry(k).or_insert(Value::Null), v);
            }
        }
        (a, b) => *a = b,
    }
}

https://stackoverflow.com/questions/47070876/how-can-i-merge-two-json-objects-with-rust

since we know the signature has no nested objects we don't need the recursive step

[ruvaag]

super neat – thanks for pointing this out. will push a fix in just a bit

[ruvaag]

just pushed and refactord it to be more concise:

    // Serialize tx, sig and constructed a merged json string
    let mut tx = serde_json::to_value(&tx)?;
    let tx_map = tx.as_object_mut().unwrap();

    serde_json::to_value(sig)?.as_object().unwrap().iter().for_each(|(k, v)| {
        tx_map.entry(k).or_insert(v.clone());
    });

[mattsse]

lgtm

[mattsse]

gas diffs unrelated