UUID.properties() crashes because "0" is not a valid UUID

[hashemi]

This code crashes in the beta branch:

import CodableKit
import Foundation

_ = UUID.properties()

Producing the following error:

Thread 1: Fatal error: 'try!' expression unexpectedly raised an error: Swift.DecodingError.dataCorrupted(Swift.DecodingError.Context(codingPath: [], debugDescription: "Attempted to decode UUID from invalid UUID string.", underlyingError: nil))

This also happens whenever Decodable.properties() is called on a type that has a UUID field.

This happens because CodingKeyCollector works by pretending to decode a type. When it encounters a String, it tries to decode "0":

    func decode(_ type: String.Type) throws -> String {
        result.add(type: type, atPath: codingPath)
        return "0"
    }

I was able to temporarily fix the crasher by changing that function in CodingKeyCollectorSingleValueDecoder to:

    func decode(_ type: String.Type) throws -> String {
        result.add(type: type, atPath: codingPath)
        return "00000000-0000-0000-0000-000000000000"
    }

A slightly more robust solution is to add a decode(_ type: UUID.Type) -> UUID that handles that special case.

Still, this only fixes this one case and doesn't address the class of potential errors that arise from assuming that any Decodable can be successfully decoded with an arbitrary combination of values (false, "0", 0).

[SandorDobi]

Hi,
The problem is twofold the UUID is failing to decode, but if we do like this it will raise another bug with duplicating fields.
The same error is exist with Date type field. It will not crash but it cause field duplication in properties() method call.

My ugly hack is the following. It fixes the UUID problem and the Date problem, but it is not a proper fix. The proper way is to refactor the properties array to Dictionary to avoid duplicating the fields

Change the following two methods in CodingKeyCollectorSingleValueDecoder to

func decode(_ type: Double.Type) throws -> Double {
        if result.properties.count == 0 {
            result.add(type: type, atPath: codingPath)
        } else {
            let typeName = "\(result.properties.last!.type)"
            if  typeName != "Date" {
                result.add(type: type, atPath: codingPath)
            }
        }
        return 0
    }

    func decode(_ type: String.Type) throws -> String {
        if result.properties.count == 0 {
            result.add(type: type, atPath: codingPath)
            return "0"
        } else {
            let typeName = "\(result.properties.last!.type)"
            if  typeName == "UUID" {
                return UUID.keyStringFalse.uuidString
            } else {
                result.add(type: type, atPath: codingPath)
                return "0"
            }
        }
}
 

[SandorDobi]

@tanner0101 I think it can be closed now, as swift 4.1 refactoring is in place.......