Using `String(describing: typedData)` on a Starknet typed data containing array or object elements will crash

[mluisbrown]

What happened

StarknetTypedData.Element implements CustomStringConvertible as follows:

extension StarknetTypedData.Element: CustomStringConvertible {
    public var description: String {
        switch self {
        case let .string(s):
            s
        case let .decimal(n):
            String(n)
        case let .signedDecimal(n):
            String(n)
        case let .felt(f):
            f.toHex()
        case let .signedFelt(f):
            f.toHex()
        case let .bool(b):
            String(b)
        case .object:
            String(describing: self)
        case .array:
            String(describing: self)
        }
    }
}

If the element is an object or an array, this will result in an infinite loop, since String(describing: self) will just call description from the CustomStringConvertible implementation again, and again until the stack overflows.

If you add the following test to TypedDataTests.swift you will see the crash:

    func testDescription()  {
        let description = String(describing: Self.CasesRev0.tdFeltArr)
        print(description)
    }

I chose Self.CasesRev0.tdFeltArr as it contains an array element.

Stack trace

Steps to reproduce

1. Create a StarknetTypedData that has an array or object element.
2. Pass it to String(describing:)

It will crash.

SDK Version

v0.13.1

Language version

Swift 6.2

Is there an existing issue for this?

• I have searched the existing issues and verified no issue exits for this problem.

[mluisbrown]

As a suggestion, I would say the best approach for adding CustomStringConvertible here would be just to encode the object to JSON and return the JSON string. It would be best to add that directly to StarknetTypedData and not just the Element.