Deserialize JSON with irregular content - json

Question

I have the example below, where 2 "unusual" things can happen:
if the status is NOK, the data element will not be included at all
some attributes of the elements inside list might be missing (in the example below, key2 is missing in the second element of list.
Is there a way to de-serialise an irregular JSON string using automatic deriving?
Which is the easiest/better way to handle this kind of irregular JSON in Rust? Can I avoid writing a very complex match based code to check for every possible combination?
extern crate serialize;
static JSON: &'static str = r#"
{
"status": {
"status": "OK"
},
"data": {
"container": {
"key": "value",
"list": [
{
"key1": "value1",
"key2": "value2"
},
{
"key1": "value1"
}
]
}
}
}"#;
#[deriving(Decodable, Show)]
struct Top {
status: Status,
data: Data,
}
#[deriving(Decodable, Show)]
struct Data {
container: Container,
}
#[deriving(Decodable, Show)]
struct Status {
status: String,
}
#[deriving(Decodable, Show)]
struct Container {
key: String,
list: Vec<KeyVals>,
}
#[deriving(Decodable, Show)]
struct KeyVals {
key1: String,
key2: String,
}
fn main() {
let result: Top = match serialize::json::decode(JSON) {
Ok(x) => x,
Err(why) => fail!("Failed decoding the JSON! Reason: {}", why),
};
println!("{}", result);
}
When running the code, it fails because the second element of the list is missing the key2 attribute.
task '<main>' failed at 'Failed decoding the JSON! Reason: MissingFieldError(key2)', hello.rs:56
Thank you

Answer 1

Potentially existing data can be represented via an enum. In the simplest case, with an Option.
I believe using an enum will also solve your problem.
#[deriving(Encodable, Decodable)]
enum Status {
Good(Container),
Bad,
VeryBad
}
If the Container also contains potentially existing data, then you can again use an enum to represent that.