via @irace

SafeDecodableArray.swift

import Foundation

/**
 Decode an array of objects while simply omitting any nested objects that themselves fail to be decoded.
 
 Inspired by https://stackoverflow.com/a/46369152/503916
 */
struct SafeDecodableArray<T: Decodable>: Decodable {
    /*
     An intermediate type that always succeeds at being decoded. Necessary because when iterating the
     `unkeyedContainer` below, all calls to `decode` must succeed (or the container's current index won't be
     incremented and we'll never reach the end.
     */
    private struct SafeDecodable<T: Decodable>: Decodable {
        let underlying: T?
        
        init(from decoder: Decoder) throws {
            let container = try decoder.singleValueContainer()
            
            // Just store `nil` if we can't decode this
            self.underlying = try? container.decode(T.self)
        }
    }
    
    let objects: [T]
    
    init(from decoder: Decoder) throws {
        var undecoded = try decoder.unkeyedContainer()
        var decoded: [T] = []
        
        while !undecoded.isAtEnd {
            if let underlying = try undecoded.decode(SafeDecodable<T>.self).underlying {
                decoded.append(underlying)
            }
            
            /*
             Unfortunately, I don't think we have the underlying data available here, so we don't really have
             anything to log when decoding fails.
             */
        }
        
        self.objects = decoded
    }
}