Develop a new flow by generating string literals as types from existing types

I'm running into a situation where my code snippet works perfectly in TS, but encounters errors in flow. Is there a workaround to make it function correctly in flow as well?

type field = 'me' | 'you'
type fieldWithKeyword = `${field}.keyword` // encountering errors in flow
const appendKeyword = (val:field): fieldWithKeyword => {
    return `${val}.keyword`
}
appendKeyword('me') // functions fine in TS

The goal is to define two types, field and fieldWithKeyword. The fieldWithKeyword type should be able to accept values that follow the format ${field}.keyword (for example, 'me.keyword' and 'you.keyword' are valid values for fieldWithKeyword)

typescriptflowtype

Answer №1

In the context of Flow, achieving something like that may not be feasible.

Here is an alternate approach based on your example:

type field = 'me' | 'you'
type fieldWithKeyword = 'me.keyword'|'you.keyword' //errors out in flow
const appendKeyword = (val:field): fieldWithKeyword => {
    return 'me'? 'me.keyword' :'you.keyword';
}
appendKeyword('me')

However, if you were looking for a more dynamic solution without hardcoding each string, it may require a different strategy.

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