Merge pull request #940 from napi-rs/fix-return-type

fix(napi-derive-backend): Null and Undefined return type

crates/backend/src/typegen.rs

@@ -98,6 +98,7 @@ static KNOWN_TYPES: Lazy<HashMap<&'static str, &'static str>> = Lazy::new(|| {
   map.extend([
     ("JsUndefined", "undefined"),
     ("()", "undefined"),
+    ("Undefined", "undefined"),
     ("JsNumber", "number"),
     ("i8", "number"),
     ("i16", "number"),
@@ -152,6 +153,7 @@ static KNOWN_TYPES: Lazy<HashMap<&'static str, &'static str>> = Lazy::new(|| {
     ("Either4", "{} | {} | {} | {}"),
     ("Either5", "{} | {} | {} | {} | {}"),
     ("unknown", "unknown"),
+    ("Null", "null"),
     ("null", "null"),
     ("Symbol", "symbol"),
     ("JsSymbol", "symbol"),

examples/napi/__test__/typegen.spec.ts.md

@@ -66,6 +66,8 @@ Generated by [AVA](https://avajs.dev).
     export function tsRename(a: { foo: number }): string[]␊
     export function xxh64Alias(input: Buffer): BigInt␊
     export function mapOption(val?: number | undefined | null): number | undefined | null␊
+    export function returnNull(): null␊
+    export function returnUndefined(): void␊
     export function add(a: number, b: number): number␊
     export function fibonacci(n: number): number␊
     export function listObjKeys(obj: object): Array<string>␊

examples/napi/__test__/values.spec.ts

@@ -65,6 +65,8 @@ import {
   ALIAS,
   AliasedStruct,
   appendBuffer,
+  returnNull,
+  returnUndefined,
 } from '../'
 
 test('export const', (t) => {
@@ -192,6 +194,14 @@ test('get null', (t) => {
   }
 })
 
+test('return Null', (t) => {
+  t.is(returnNull(), null)
+})
+
+test('return Undefined', (t) => {
+  t.is(returnUndefined(), undefined)
+})
+
 test('pass symbol in', (t) => {
   const sym = Symbol('test')
   const obj = setSymbolInObj(sym)

examples/napi/index.d.ts

@@ -56,6 +56,8 @@ export function mutateExternal(external: ExternalObject<number>, newVal: number)
 export function tsRename(a: { foo: number }): string[]
 export function xxh64Alias(input: Buffer): BigInt
 export function mapOption(val?: number | undefined | null): number | undefined | null
+export function returnNull(): null
+export function returnUndefined(): void
 export function add(a: number, b: number): number
 export function fibonacci(n: number): number
 export function listObjKeys(obj: object): Array<string>

examples/napi/src/nullable.rs

@@ -1,4 +1,14 @@
+use napi::bindgen_prelude::*;
+
 #[napi]
 fn map_option(val: Option<u32>) -> Option<u32> {
   val.map(|v| v + 1)
 }
+
+#[napi]
+fn return_null() -> Null {
+  Null
+}
+
+#[napi]
+fn return_undefined() -> Undefined {}