Fix BigInt issue with zero value

Looks like 0 is a special case: 4318b2348d/deps/v8/src/objects/bigint.cc (L1595-L1602)

crates/napi/src/bindgen_runtime/js_values/bigint.rs

@@ -64,6 +64,9 @@ impl FromNapiValue for BigInt {
 
       words.set_len(word_count as usize);
     }
+    if word_count == 0 {
+      words = vec![0];
+    }
     Ok(BigInt {
       sign_bit: sign_bit == 1,
       words,

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

@@ -31,6 +31,7 @@ Generated by [AVA](https://avajs.dev).
     export function bigintAdd(a: bigint, b: bigint): bigint␊
     export function createBigInt(): bigint␊
     export function createBigIntI64(): bigint␊
+    export function bigintGetU64AsString(bi: bigint): string␊
     export function getCwd(callback: (arg0: string) => void): void␊
     export function optionEnd(callback: (arg0: string, arg1?: string | undefined | null) => void): void␊
     export function optionStart(callback: (arg0: string | undefined | null, arg1: string) => void): void␊

examples/napi/__test__/values.spec.ts

@@ -43,6 +43,7 @@ import {
   bigintAdd,
   createBigInt,
   createBigIntI64,
+  bigintGetU64AsString,
   callThreadsafeFunction,
   threadsafeFunctionThrowError,
   asyncPlus100,
@@ -423,6 +424,10 @@ BigIntTest('create BigInt i64', (t) => {
   t.is(createBigIntI64(), BigInt(100))
 })
 
+BigIntTest('BigInt get_u64', (t) => {
+  t.is(bigintGetU64AsString(BigInt(0)), '0')
+})
+
 BigIntTest('js mod test', (t) => {
   t.is(xxh64Alias(Buffer.from('hello world')), BigInt('1116'))
   t.is(xxh3.xxh3_64(Buffer.from('hello world')), BigInt('1116'))

examples/napi/index.d.ts

@@ -21,6 +21,7 @@ export function asyncMultiTwo(arg: number): Promise<number>
 export function bigintAdd(a: bigint, b: bigint): bigint
 export function createBigInt(): bigint
 export function createBigIntI64(): bigint
+export function bigintGetU64AsString(bi: bigint): string
 export function getCwd(callback: (arg0: string) => void): void
 export function optionEnd(callback: (arg0: string, arg1?: string | undefined | null) => void): void
 export function optionStart(callback: (arg0: string | undefined | null, arg1: string) => void): void

examples/napi/src/bigint.rs

@@ -17,3 +17,8 @@ fn create_big_int() -> BigInt {
 fn create_big_int_i64() -> i64n {
   i64n(100)
 }
+
+#[napi]
+pub fn bigint_get_u64_as_string(bi: BigInt) -> String {
+  bi.get_u64().1.to_string()
+}