Effect CommunityEC
Effect Community•3y ago•
111 replies
attila

Declaring Fallback Values for Unknown Literals

What is the best way to declare fallback values for unknown literals? I'm tackling the problem of ensuring forward-compatibility of schemas and often I face literal values that may be extended in the future. For example: const planType = Schema.literal("lite", "professional", "enterprise"). Let's say someone introduces a new plan type enterprise-plus. I would not want the parsing of this schema to fail. The way I'm currently solving it is the following:

const planType = Schema.literal("lite", "professional", "enterprise", "unknown");
const parentObject = Schema.struct({
  planType: Schema.optional(planType).withDefault(() => "unknown")
});


The workaround is suboptimal for the following reasons:
- Parsing succeeds even if planType is missing or undefined, some schema users may want it to fail in such a case
- Only works if there is a parent object in which the schema can be placed, Schema.literal does not have a withDefault method on it.

I'd like to hear from you. How do you tackle forward-compatibility with schema? Am I just not aware of some API?
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