fix(napi): big numbers losing precision on serde_json::Value (#1538)

* fix(napi): big numbers losing precision on serde_json::Value

* fix(napi): add feature flags for bigint on number conversion

* chore(napi): change MAX_SAFE_INT to constant and convert big numbers to string when bigint is not available

* chore(napi): change how the check for safe integer range is made

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

@@ -4,6 +4,8 @@ use crate::{
   bindgen_runtime::Null, check_status, sys, type_of, Error, JsObject, Result, Status, ValueType,
 };
 
+#[cfg(feature = "napi6")]
+use super::BigInt;
 use super::{FromNapiValue, Object, ToNapiValue};
 
 impl ToNapiValue for Value {
@@ -111,14 +113,30 @@ impl FromNapiValue for Map<String, Value> {
 
 impl ToNapiValue for Number {
   unsafe fn to_napi_value(env: sys::napi_env, n: Self) -> Result<sys::napi_value> {
+    #[cfg(feature = "napi6")]
+    const MAX_SAFE_INT: i64 = 9007199254740991i64; // 2 ^ 53 - 1
     if n.is_i64() {
-      unsafe { i64::to_napi_value(env, n.as_i64().unwrap()) }
+      let n = n.as_i64().unwrap();
+      #[cfg(feature = "napi6")]
+      {
+        if !(-MAX_SAFE_INT..=MAX_SAFE_INT).contains(&n) {
+          return unsafe { BigInt::to_napi_value(env, BigInt::from(n)) };
+        }
+      }
+
+      unsafe { i64::to_napi_value(env, n) }
     } else if n.is_f64() {
       unsafe { f64::to_napi_value(env, n.as_f64().unwrap()) }
     } else {
       let n = n.as_u64().unwrap();
       if n > u32::MAX as u64 {
-        todo!("impl BigInt")
+        #[cfg(feature = "napi6")]
+        {
+          return unsafe { BigInt::to_napi_value(env, BigInt::from(n)) };
+        }
+
+        #[cfg(not(feature = "napi6"))]
+        return unsafe { String::to_napi_value(env, n.to_string()) };
       } else {
         unsafe { u32::to_napi_value(env, n as u32) }
       }

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

@@ -195,6 +195,7 @@ Generated by [AVA](https://avajs.dev).
     export function readPackageJson(): PackageJson␊
     export function getPackageJsonName(packageJson: PackageJson): string␊
     export function testSerdeRoundtrip(data: any): any␊
+    export function testSerdeBigNumberPrecision(number: string): any␊
     export function returnFromSharedCrate(): Shared␊
     export function contains(source: string, target: string): boolean␊
     export function concatStr(s: string): string␊

examples/napi/__test__/values.spec.ts

@@ -90,6 +90,7 @@ import {
   getStrFromObject,
   returnJsFunction,
   testSerdeRoundtrip,
+  testSerdeBigNumberPrecision,
   createObjWithProperty,
   receiveObjectOnlyFromJs,
   dateToNumber,
@@ -495,6 +496,23 @@ test('serde-roundtrip', (t) => {
   t.is(err!.message, 'JS symbols cannot be represented as a serde_json::Value')
 })
 
+test('serde-large-number-precision', (t) => {
+  t.is(testSerdeBigNumberPrecision('12345').number, 12345)
+  t.is(
+    testSerdeBigNumberPrecision('123456789012345678901234567890').number,
+    1.2345678901234568e29,
+  )
+  t.is(
+    testSerdeBigNumberPrecision('123456789012345678901234567890.123456789')
+      .number,
+    1.2345678901234568e29,
+  )
+  t.is(
+    testSerdeBigNumberPrecision('109775245175819965').number.toString(),
+    '109775245175819965',
+  )
+})
+
 test('buffer', (t) => {
   let buf = getBuffer()
   t.is(buf.toString('utf-8'), 'Hello world')

examples/napi/index.d.ts

@@ -185,6 +185,7 @@ export interface PackageJson {
 export function readPackageJson(): PackageJson
 export function getPackageJsonName(packageJson: PackageJson): string
 export function testSerdeRoundtrip(data: any): any
+export function testSerdeBigNumberPrecision(number: string): any
 export function returnFromSharedCrate(): Shared
 export function contains(source: string, target: string): boolean
 export function concatStr(s: string): string

examples/napi/src/serde.rs

@@ -30,3 +30,9 @@ fn get_package_json_name(package_json: PackageJson) -> String {
 fn test_serde_roundtrip(data: Value) -> Value {
   data
 }
+
+#[napi]
+fn test_serde_big_number_precision(number: String) -> Value {
+  let data = format!("{{\"number\":{}}}", number);
+  serde_json::from_str(&data).unwrap()
+}