feat: rename $.stringUnion to $.literalUnion (#137)

tjjfvi · Feb 20, 2023 · 5a6465a · 5a6465a
1 parent c931071
commit 5a6465a
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Showing 5 changed files with 38 additions and 30 deletions.
diff --git a/codecs/test/__snapshots__/union.test.ts.snap b/codecs/test/__snapshots__/union.test.ts.snap
@@ -44,33 +44,33 @@ e7
 00
 `;
 
-snapshot[`\$.stringUnion(names) "Ross" 1`] = `00`;
+snapshot[`\$.literalUnion(names) "Ross" 1`] = `00`;
 
-snapshot[`\$.stringUnion(names) "Alisa" 1`] = `01`;
+snapshot[`\$.literalUnion(names) "Alisa" 1`] = `01`;
 
-snapshot[`\$.stringUnion(names) "Stefan" 1`] = `02`;
+snapshot[`\$.literalUnion(names) "Stefan" 1`] = `02`;
 
-snapshot[`\$.stringUnion(names) "Raoul" 1`] = `03`;
+snapshot[`\$.literalUnion(names) "Raoul" 1`] = `03`;
 
-snapshot[`\$.stringUnion(names) "James" 1`] = `04`;
+snapshot[`\$.literalUnion(names) "James" 1`] = `04`;
 
-snapshot[`\$.stringUnion(names) "David" 1`] = `05`;
+snapshot[`\$.literalUnion(names) "David" 1`] = `05`;
 
-snapshot[`\$.stringUnion(names) "Pierre" 1`] = `06`;
+snapshot[`\$.literalUnion(names) "Pierre" 1`] = `06`;
 
-snapshot[`\$.stringUnion(interestingU8s) "Min" 1`] = `00`;
+snapshot[`\$.literalUnion(interestingU8s) "Min" 1`] = `00`;
 
-snapshot[`\$.stringUnion(interestingU8s) "Unit" 1`] = `01`;
+snapshot[`\$.literalUnion(interestingU8s) "Unit" 1`] = `01`;
 
-snapshot[`\$.stringUnion(interestingU8s) "EvenPrime" 1`] = `02`;
+snapshot[`\$.literalUnion(interestingU8s) "EvenPrime" 1`] = `02`;
 
-snapshot[`\$.stringUnion(interestingU8s) "LargestPerfect" 1`] = `1c`;
+snapshot[`\$.literalUnion(interestingU8s) "LargestPerfect" 1`] = `1c`;
 
-snapshot[`\$.stringUnion(interestingU8s) "FirstUninteresting" 1`] = `81`;
+snapshot[`\$.literalUnion(interestingU8s) "FirstUninteresting" 1`] = `81`;
 
-snapshot[`\$.stringUnion(interestingU8s) "LargestSquare" 1`] = `e1`;
+snapshot[`\$.literalUnion(interestingU8s) "LargestSquare" 1`] = `e1`;
 
-snapshot[`\$.stringUnion(interestingU8s) "Max" 1`] = `ff`;
+snapshot[`\$.literalUnion(interestingU8s) "Max" 1`] = `ff`;
 
 snapshot[`\$abc invalid null 1`] = `ScaleAssertError: value == null`;
 

diff --git a/codecs/test/union.test.ts b/codecs/test/union.test.ts
@@ -22,7 +22,7 @@ const interestingU8s = {
   255: "Max",
 } as const
 
-const $interestingU8s = $.withMetadata(metadata("$.stringUnion(interestingU8s)"), $.stringUnion(interestingU8s))
+const $interestingU8s = $.withMetadata(metadata("$.literalUnion(interestingU8s)"), $.literalUnion(interestingU8s))
 
 const names = [
   "Ross",
@@ -34,7 +34,7 @@ const names = [
   "Pierre",
 ] as const
 
-const $names = $.withMetadata(metadata("$.stringUnion(names)"), $.stringUnion(names))
+const $names = $.withMetadata(metadata("$.literalUnion(names)"), $.literalUnion(names))
 
 testCodec($abc, [
   { _tag: "A" },

diff --git a/codecs/union.ts b/codecs/union.ts
@@ -26,8 +26,8 @@ export type NativeTaggedUnion<
 
 export function taggedUnion<
   K extends keyof any,
-  M extends Record<number, Variant<any, any>>,
->(tagKey: K, members: Narrow<M>): Codec<NativeTaggedUnion<K, M>> {
+  M extends [] | Record<number, Variant<any, any>>,
+>(tagKey: K, members: M): Codec<NativeTaggedUnion<K, M>> {
   const tagToDiscriminant: Record<string, number> = Object.create(null)
   const discriminantToMember: Record<number, Codec<any>> = Object.create(null)
   for (const _discriminant in members) {
@@ -65,19 +65,19 @@ export function taggedUnion<
   })
 }
 
-export function stringUnion<T extends string>(members: Record<number, T>): Codec<T> {
-  const keyToDiscriminant: Record<string, number> = Object.create(null)
+export function literalUnion<T extends Narrow>(members: Record<number, T>): Codec<T> {
+  const keyToDiscriminant: Map<T, number> = new Map()
   for (const _discriminant in members) {
     const discriminant = +_discriminant
     if (isNaN(discriminant)) continue
-    const key = members[discriminant]!
-    keyToDiscriminant[key] = discriminant
+    const key = members[discriminant] as T
+    keyToDiscriminant.set(key, discriminant)
   }
   return createCodec({
-    _metadata: metadata("$.stringUnion", stringUnion, members),
+    _metadata: metadata("$.literalUnion", literalUnion, members),
     _staticSize: 1,
     _encode(buffer, value) {
-      const discriminant = keyToDiscriminant[value]!
+      const discriminant = keyToDiscriminant.get(value)!
       buffer.array[buffer.index++] = discriminant
     },
     _decode(buffer) {
@@ -86,7 +86,7 @@ export function stringUnion<T extends string>(members: Record<number, T>): Codec
     },
     _assert(assert) {
       assert.typeof(this, "string")
-      if (!((assert.value as string) in keyToDiscriminant)) {
+      if (!keyToDiscriminant.has(assert.value as T)) {
         throw new ScaleAssertError(this, assert.value, `${assert.path} invalid value`)
       }
     },

diff --git a/common/util.ts b/common/util.ts
@@ -30,7 +30,15 @@ export class ScaleDecodeError extends ScaleError {
 
 export type Expand<T> = T extends T ? { [K in keyof T]: T[K] } : never
 export type U2I<U> = (U extends U ? (u: U) => 0 : never) extends (i: infer I) => 0 ? Extract<I, U> : never
-export type Narrow<T> =
-  | (T extends infer U ? U : never)
-  | Extract<T, number | string | boolean | bigint | symbol | null | undefined | []>
-  | ([T] extends [[]] ? [] : { [K in keyof T]: Narrow<T[K]> })
+
+type _Narrow<T, U> = [U] extends [T] ? U : Extract<T, U>
+export type Narrow<T = unknown> =
+  | _Narrow<T, 0 | number & {}>
+  | _Narrow<T, 0n | bigint & {}>
+  | _Narrow<T, "" | string & {}>
+  | _Narrow<T, boolean>
+  | _Narrow<T, symbol>
+  | _Narrow<T, []>
+  | _Narrow<T, { [_: PropertyKey]: Narrow }>
+  | (T extends object ? { [K in keyof T]: Narrow<T[K]> } : never)
+  | Extract<{} | null | undefined, T>
diff --git a/examples/unions.eg.ts b/examples/unions.eg.ts
@@ -31,7 +31,7 @@ $pet
 //   | { type: "cat"; purr: string; name: string }
 // >
 
-export const $dinosaur = $.stringUnion([
+export const $dinosaur = $.literalUnion([
   "Liopleurodon",
   "Kosmoceratops",
   "Psittacosaurus",