U256 deserialization fails for dec_str

[0xrainbowtrout]

Version
List the versions of all ethers-rs crates you are using. The easiest way to get this information is using cargo-tree.

├── ethers v2.0.3
│   ├── ethers-addressbook v2.0.3
│   │   ├── ethers-core v2.0.3
│   ├── ethers-contract v2.0.3
│   │   ├── ethers-contract-abigen v2.0.3
│   │   │   ├── ethers-core v2.0.3 (*)
│   │   │   ├── ethers-etherscan v2.0.3
│   │   │   │   ├── ethers-core v2.0.3 (*)
│   │   │   │   ├── ethers-solc v2.0.3
│   │   │   │   │   ├── ethers-core v2.0.3 (*)
│   │   ├── ethers-contract-derive v2.0.3 (proc-macro)
│   │   │   ├── ethers-contract-abigen v2.0.3
│   │   │   │   ├── ethers-core v2.0.3 (*)
│   │   │   ├── ethers-core v2.0.3 (*)
│   │   ├── ethers-core v2.0.3 (*)
│   │   ├── ethers-providers v2.0.3
│   │   │   ├── ethers-core v2.0.3 (*)
│   ├── ethers-core v2.0.3 (*)
│   ├── ethers-etherscan v2.0.3 (*)
│   ├── ethers-middleware v2.0.3
│   │   ├── ethers-contract v2.0.3 (*)
│   │   ├── ethers-core v2.0.3 (*)
│   │   ├── ethers-etherscan v2.0.3 (*)
│   │   ├── ethers-providers v2.0.3 (*)
│   │   ├── ethers-signers v2.0.3
│   │   │   ├── ethers-core v2.0.3 (*)
│   ├── ethers-providers v2.0.3 (*)
│   ├── ethers-signers v2.0.3 (*)
│   └── ethers-solc v2.0.3 (*)

Platform
The output of uname -a (UNIX), or version and 32 or 64-bit (Windows)

Linux XXXXXXXX 6.2.9-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 30 Mar 2023 14:51:14 +0000 x86_64

Description

I was trying to read data from a json that consists of a number of U256s and kept getting unexpected results (the numbers were getting deserialized incorrectly). It appears related to #1507. See a simplified code sample below:

use ethers::core::types::U256;
use serde::{Deserialize, Deserializer, Serialize};
use serde_json::{Result, Value};


#[test]
fn deserialize_u256() {

    #[derive(Debug, Deserialize, Serialize)]
    struct TestValues {
        value_1: U256,
        value_2: U256,
        value_3: U256,
        value_4: U256,
    }

    let data = r#"
        {
            "value_1": "750000000000000000",
            "value_2": "21000000000000000",
            "value_3": "0",
            "value_4": "1"
        }
    "#;
            
    let data_json: TestValues = serde_json::from_str(&data).unwrap();

    println!("Expected {:?}, got {:?}", U256::from_dec_str("750000000000000000").unwrap(), data_json.value_1);
    println!("Expected {:?}, got {:?}", U256::from_dec_str("21000000000000000").unwrap(), data_json.value_2);
    println!("Expected {:?}, got {:?}", U256::from_dec_str("0").unwrap(), data_json.value_3);
    println!("Expected {:?}, got {:?}", U256::from_dec_str("1").unwrap(), data_json.value_4);

    assert_eq!(data_json.value_1, U256::from_dec_str("750000000000000000").unwrap());
    assert_eq!(data_json.value_2, U256::from_dec_str("21000000000000000").unwrap());
    assert_eq!(data_json.value_3, U256::zero());
    assert_eq!(data_json.value_4, U256::one());
}

The output of this is:

---- deserialize_u256 stdout ----
Expected 750000000000000000, got 2158269056624017539072
Expected 21000000000000000, got 38046409652025950208
Expected 0, got 0
Expected 1, got 1
thread 'deserialize_u256' panicked at 'assertion failed: `(left == right)`
  left: `2158269056624017539072`,
 right: `750000000000000000`', tests/deserialize_u256.rs:33:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

---- deserialize_rate_model stdout ----
rateModel: RateModelConfig { rateModel: RateModel { u_bar: 2158269056624017539072, r_0: 38046409652025950208, r_1: 0, r_2: 1770887431076116955136 }, routeRateModel: RouteRateModel { models: {"1-10": RateModel { u_bar: 0, r_0: 0, r_1: 0, r_2: 0 }, "1-42161": RateModel { u_bar: 0, r_0: 0, r_1: 0, r_2: 0 }} }, transferThreshold: "0", spokeTargetBalances: SpokeTargetBalances { targets: {"42161": SpokeTarget { threshold: 6044629098073145873530880, target: 4004566777473459141214208 }, "10": SpokeTarget { threshold: 6044629098073145873530880, target: 4004566777473459141214208 }} } }
thread 'deserialize_rate_model' panicked at 'assertion failed: `(left == right)`
  left: `2158269056624017539072`,
 right: `750000000000000000`', tests/deserialize_u256.rs:92:5

It seems similar to #1507 because HEX(750000000000000000) -> 2158269056624017539072. I took a look at what I think are the relevant lines of code and I'm not sure why it's landing on else if s.starts_with("0x") -- It could be me doing something dumb but the behaviour seemed unexpected.

[mattsse]

I took a look at what I think are the relevant lines of code a

but that's not even used here

see #2354

[0xrainbowtrout]

got it. thank you!