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New Feature: add TaggedUnionType #183

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merged 1 commit into from
Aug 11, 2018
Merged

New Feature: add TaggedUnionType #183

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26 changes: 23 additions & 3 deletions src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1113,11 +1113,30 @@ export const getTagValue = <Tag extends string>(tag: Tag): ((type: Tagged<Tag>)
return f
}

export class TaggedUnionType<
Tag extends string,
RTS extends Array<Tagged<Tag>>,
A = any,
O = A,
I = mixed
> extends UnionType<RTS, A, O, I> {
constructor(
name: string,
is: TaggedUnionType<Tag, RTS, A, O, I>['is'],
validate: TaggedUnionType<Tag, RTS, A, O, I>['validate'],
serialize: TaggedUnionType<Tag, RTS, A, O, I>['encode'],
types: RTS,
readonly tag: Tag
) {
super(name, is, validate, serialize, types) /* istanbul ignore next */ // <= workaround for https://github.com/Microsoft/TypeScript/issues/13455
}
}

export const taggedUnion = <Tag extends string, RTS extends Array<Tagged<Tag>>>(
tag: Tag,
types: RTS,
name: string = `(${types.map(type => type.name).join(' | ')})`
): UnionType<RTS, TypeOf<RTS['_A']>, OutputOf<RTS['_A']>, mixed> => {
): TaggedUnionType<Tag, RTS, TypeOf<RTS['_A']>, OutputOf<RTS['_A']>, mixed> => {
const len = types.length
const values: Array<string | number | boolean> = new Array(len)
const hash: { [key: string]: number } = {}
Expand Down Expand Up @@ -1149,7 +1168,7 @@ export const taggedUnion = <Tag extends string, RTS extends Array<Tagged<Tag>>>(
(m, c) => (isTagValue(m) ? success(m) : failure(m, c)),
identity
)
return new UnionType<RTS, TypeOf<RTS['_A']>, OutputOf<RTS['_A']>, mixed>(
return new TaggedUnionType<Tag, RTS, TypeOf<RTS['_A']>, OutputOf<RTS['_A']>, mixed>(
name,
(v): v is TypeOf<RTS['_A']> => {
if (!Dictionary.is(v)) {
Expand All @@ -1175,7 +1194,8 @@ export const taggedUnion = <Tag extends string, RTS extends Array<Tagged<Tag>>>(
}
},
useIdentity(types, len) ? identity : a => types[getIndex(a[tag] as any)].encode(a),
types
types,
tag
)
}

Expand Down