kengr

Posted by Remy Porter

https://thedailywtf.com/articles/pawn-pawn-in-in-game-game-of-of-life-life

It feels like ages ago, when document databases like Mongo were all the rage. That isn't to say that they haven't stuck around and don't deliver value, but gone is the faddish "RDBMSes are dead, bro." The "advantage" they offer is that they turn data management problems into serialization problems.

And that's where today's anonymous submission takes us. Our submitter has a long list of bugs around managing lists of usernames. These bugs largely exist because the contract developer who wrote the code didn't write anything, and instead "vibe coded too close to the sun", according to our submitter.

Here's the offending C# code:

   [JsonPropertyName("invitedTraders")]
   [BsonElement("invitedTraders")]
   [BsonIgnoreIfNull]
   public InvitedTradersV2? InvitedTraders { get; set; }

   [JsonPropertyName("invitedTradersV2")]
   [BsonElement("invitedTradersV2")]
   [BsonIgnoreIfNull]
   public List<string>? InvitedTradersV2 { get; set; }

Let's start with the type InvitedTradersV2. This type contains a list of strings which represent usernames. The field InvitedTradersV2 is a list of strings which represent usernames. Half of our submitter's bugs exist simply because these two lists get out of sync- they should contain the same data, but without someone enforcing that correctly, problems accrue.

This is made more frustrating by the MongoDB attribute, BsonIgnoreIfNull, which simply means that the serialized object won't contain the key if the value is null. But that means the consuming application doesn't know which key it should check.

For the final bonus fun, note the use of JsonPropertyName. This comes from the built-in class library, which tells .NET how to serialize the object to JSON. The problem here is that this application doesn't use the built-in serializer, and instead uses Newtonsoft.JSON, a popular third-party library for solving the problem. While Newtonsoft does recognize some built-in attributes for serialization, JsonPropertyName is not among them. This means that property does nothing in this example, aside from add some confusion to the code base.

I suspect the developer responsible, if they even read this code, decided that the duplicated data was okay, because isn't that just a normal consequence of denormalization? And document databases are all about denormalization. It makes your queries faster, bro. Just one more shard, bro.

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https://thedailywtf.com/articles/pawn-pawn-in-in-game-game-of-of-life-life