index out of bounds: the len is 0 but the index is 0

[fergarrui]

Component

Forge

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

forge 0.2.0 (6570a4c 2023-03-23T00:04:51.797681082Z)

What command(s) is the bug in?

forge script

Operating System

Linux

Describe the bug

When using vm.parseJsonUint on a json where the key is not found I'm getting:

The application panicked (crashed).
Message:  index out of bounds: the len is 0 but the index is 0
Location: evm/src/executor/inspector/cheatcodes/ext.rs:424

This is a bug. Consider reporting it at https://github.com/foundry-rs/foundry

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
   1: __libc_start_main<unknown>
      at /build/glibc-sMfBJT/glibc-2.31/csu/../csu/libc-start.c:308

It happened to me having a JSON like:

{
  "local": {
    "prop1": 10,
  }
}

Used to work in previous versions:

vm.parseJsonUint(configJson, "local.prop1")

With latest I get this error:

Error: 
path error: 
$local.prop1
^^^^^^

Then I saw that jq syntax is required now, so when I do (it starts with a dot . now):

vm.parseJsonUint(configJson, ".local.prop1")

Is when I get the crash.
In my use case, I check if prop1 exists in some objects in the JSON, but when it is not found is when it crashes.

[mattsse]

I was unable to reproduce this

       function test_repro() public {
        string memory path = "./Issue4630.json";
        string memory json = vm.readFile(path);
        uint256 val = vm.parseJsonUint(json, ".local.prop1");
        console.log(val);
    }

with

{
    "local": {
        "prop1": 10
    }
}

[mattsse]

but there's a panic if the object is empty, so I'll fix that:

{
    "local": {}
}

[fergarrui]

@mattsse Yes that's right sorry the issue happens when the property is not found.

Thanks!

[karmacoma-eth]

Wanted to confirm this, here is an alternative repro:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;

import {stdJson} from "forge-std/StdJson.sol";

import "forge-std/Test.sol";

contract JsonTest is Test {
    function testJson() public {
        string memory json = '{"name":"John","age":30,"city":"New York"}';

        // works
        assertEq(stdJson.readString(json, ".name"), "John");

        // crashes with
        //  The application panicked (crashed).
        //  Message:  index out of bounds: the len is 0 but the index is 0
        //  Location: evm/src/executor/inspector/cheatcodes/ext.rs:424
        stdJson.readString(json, ".darkest_secret");
    }
}

Running a git bisect points at f8e700 being the first bad commit where this started happening

[mattsse]

should be fixed via #4631