perf(napi): optimize primitive napi functions (denoland#16163)

littledivy · web-flow · commit 5bc2bfdfbca5 · 2022-10-07T16:24:01.000+05:30
This optimization applies on `napi_get_undefined`, `napi_get_null` &amp;
`napi_get_boolean`.

```
# main

benchmark               time (avg)             (min &hellip; max)       p75       p99      p995
---------------------------------------------------------- -----------------------------
warmup              482.55 ps/iter   (462.5 ps &hellip; 15.67 ns)    475 ps    525 ps  829.1 ps
napi_get_undefined   25.07 ns/iter   (24.03 ns &hellip; 36.87 ns)  25.37 ns  27.09 ns  34.85 ns
```

```
# This patch

benchmark               time (avg)             (min &hellip; max)       p75       p99      p995
---------------------------------------------------------- -----------------------------
warmup              484.78 ps/iter    (462.5 ps &hellip; 14.4 ns)    475 ps  554.1 ps  583.3 ps
napi_get_undefined   15.52 ns/iter   (15.35 ns &hellip; 22.14 ns)  15.41 ns  17.18 ns  20.02 ns
```
diff --git a/serde_v8/ser.rs b/serde_v8/ser.rs
@@ -3,6 +3,7 @@ use serde::ser;
 use serde::ser::Serialize;
 
 use std::cell::RefCell;
+use std::ops::DerefMut;
 
 use crate::error::{Error, Result};
 use crate::keys::v8_struct_key;
@@ -435,7 +436,8 @@ impl<'a, 'b, 'c> ser::Serializer for Serializer<'a, 'b, 'c> {
   }
 
   fn serialize_f64(self, v: f64) -> JsResult<'a> {
-    Ok(v8::Number::new(&mut self.scope.borrow_mut(), v).into())
+    let scope = &mut self.scope.borrow_mut();
+    Ok(v8::Number::new(scope.deref_mut(), v).into())
   }
 
   fn serialize_bool(self, v: bool) -> JsResult<'a> {

Original file line number	Diff line number	Diff line change
`@@ -3,6 +3,7 @@ use serde::ser;`
`3`	`3`	`use serde::ser::Serialize;`
`4`	`4`
`5`	`5`	`use std::cell::RefCell;`
	`6`	`+use std::ops::DerefMut;`
`6`	`7`
`7`	`8`	`use crate::error::{Error, Result};`
`8`	`9`	`use crate::keys::v8_struct_key;`
`@@ -435,7 +436,8 @@ impl<'a, 'b, 'c> ser::Serializer for Serializer<'a, 'b, 'c> {`
`435`	`436`	`}`
`436`	`437`
`437`	`438`	`fn serialize_f64(self, v: f64) -> JsResult<'a> {`
`438`		`- Ok(v8::Number::new(&mut self.scope.borrow_mut(), v).into())`
	`439`	`+ let scope = &mut self.scope.borrow_mut();`
	`440`	`+ Ok(v8::Number::new(scope.deref_mut(), v).into())`
`439`	`441`	`}`
`440`	`442`
`441`	`443`	`fn serialize_bool(self, v: bool) -> JsResult<'a> {`