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kotlinlang

I'm deserializing some very dirty data that I don't have any control over
Example:
```{
    "field1":"a field that's always there"
    "field2":"a field that's sometimes there, other times not and the content varies from Boolean to String to Dates to numbers"
}```
Is it possible to have `ignoreUnknownKeys=false` and then have a list of fields that I can ignore?
I want it to throw an error if they send for example JSON that now has a `field3`, but I don't want to care about `field2` and I definitely don't want it in my model.

I'm already using a custom JsonContentPolymorphicSerializer so that I can switch between different types for one of the other fields

the first suggestion that springs to mind would be

• set the type of `field2` to be `JsonElement`, 
• and have `field2` defined in code but document it as `@Deprecated` - perhaps even with the visibility set to ‘hidden’

another idea:

• define `@Serializable(with = IgnoredFieldSerializer::class) object IgnoredField`
• set `IgnoredFieldSerializer` descriptor to be a primitive, and configure it so it will always decode to object `IgnoredField`, and encode nothing, or `null`
• set `val field2: IgnoredField?`