Handle multiple repeated aliases

[JP-Ellis]

Summary

Could or should serde_json handle input where a field has multiple aliases, and both aliases are present?

Background

I would like to support handling deserialising from either of two aliases, even in situations where both are provided.

In my particular case, we are migrating one endpoint from snake_case to camelCase, and to preserve some backwards compatibility as end-users transition, there will be an interim period where data is duplicated and returned in both formats (in a standard 'expand and contract' pattern).

As a result, we have code that looks like:

#[derive(Debug, Serialize, Deserialize)]
struct StatusResponse {
  #[serde(alias = "session_id", alias = "sessionId")]
  session_id: String
}

and we need to be able to deserialize the payload:

{
	"session_id": "123",
    "sessionId": "123"
}

Alternative

While the 'expand-and-contract' approach from the server is preferred, if the answer here is a 'no', the alternative would be to expand-and-contract from the client side, and have a hard-transition at some point from the server's perspective.

Related

I have looked into other tickets, and while I could find what I'm asking for exactly, there were some related items:

• Checking for duplicate keys #1112
• Add feature to error on duplicate key in Map<String, Value> #1113
• Consider returning an error on duplicate keys by default #762