feat(napi-derive): allow injecting this in class method

crates/backend/src/codegen/fn.rs

@@ -12,7 +12,7 @@ impl TryToTokens for NapiFn {
     let intermediate_ident = get_intermediate_ident(&name_str);
     let args_len = self.args.len();
 
-    let (arg_conversions, arg_names) = self.gen_arg_conversions();
+    let (arg_conversions, arg_names) = self.gen_arg_conversions()?;
     let receiver = self.gen_fn_receiver();
     let receiver_ret_name = Ident::new("_ret", Span::call_site());
     let ret = self.gen_fn_return(&receiver_ret_name);
@@ -93,7 +93,7 @@ impl TryToTokens for NapiFn {
 }
 
 impl NapiFn {
-  fn gen_arg_conversions(&self) -> (Vec<TokenStream>, Vec<TokenStream>) {
+  fn gen_arg_conversions(&self) -> BindgenResult<(Vec<TokenStream>, Vec<TokenStream>)> {
     let mut arg_conversions = vec![];
     let mut args = vec![];
 
@@ -117,7 +117,7 @@ impl NapiFn {
     }
 
     let mut skipped_arg_count = 0;
-    self.args.iter().enumerate().for_each(|(i, arg)| {
+    for (i, arg) in self.args.iter().enumerate() {
       let i = i - skipped_arg_count;
       let ident = Ident::new(&format!("arg{}", i), Span::call_site());
 
@@ -127,27 +127,41 @@ impl NapiFn {
             args.push(quote! { napi::bindgen_prelude::Env::from(env) });
             skipped_arg_count += 1;
           } else {
-            if self.parent.is_some() {
+            let is_in_class = self.parent.is_some();
             if let syn::Type::Path(path) = path.ty.as_ref() {
               if let Some(p) = path.path.segments.last() {
                 if p.ident == "Reference" {
-                    if let syn::PathArguments::AngleBracketed(
-                      syn::AngleBracketedGenericArguments { args: angle_bracketed_args, .. },
-                    ) = &p.arguments
+                  if !is_in_class {
+                    bail_span!(p, "`Reference` is only allowed in class methods");
+                  }
+                  if let syn::PathArguments::AngleBracketed(syn::AngleBracketedGenericArguments {
+                    args: angle_bracketed_args,
+                    ..
+                  }) = &p.arguments
+                  {
+                    if let Some(syn::GenericArgument::Type(syn::Type::Path(path))) =
+                      angle_bracketed_args.first()
                     {
-                      if let Some(syn::GenericArgument::Type(syn::Type::Path(path))) = angle_bracketed_args.first() {
                       if let Some(p) = path.path.segments.first() {
                         if p.ident == *self.parent.as_ref().unwrap() {
                           args.push(
                               quote! { napi::bindgen_prelude::Reference::from_value_ptr(this_ptr as *mut std::ffi::c_void, env)? },
                             );
                           skipped_arg_count += 1;
-                              return;
+                          continue;
                         }
                       }
                     }
                   }
+                } else if p.ident == "This" {
+                  if !is_in_class {
+                    bail_span!(p, "`This` is only allowed in class methods");
                   }
+                  args.push(
+                    quote! { <napi::bindgen_prelude::This as napi::NapiValue>::from_raw_unchecked(env, cb.this) },
+                  );
+                  skipped_arg_count += 1;
+                  continue;
                 }
               }
             }
@@ -160,9 +174,9 @@ impl NapiFn {
           args.push(quote! { #ident });
         }
       }
-    });
+    }
 
-    (arg_conversions, args)
+    Ok((arg_conversions, args))
   }
 
   fn gen_ty_arg_conversion(

crates/backend/src/typegen.rs

@@ -214,6 +214,7 @@ static KNOWN_TYPES: Lazy<HashMap<&'static str, &'static str>> = Lazy::new(|| {
     ("unknown", "unknown"),
     ("Unknown", "unknown"),
     ("JsUnknown", "unknown"),
+    ("This", "this")
   ]);
 
   map

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

@@ -2,7 +2,9 @@ use std::any::type_name;
 use std::ops::{Deref, DerefMut};
 use std::ptr;
 
-use crate::{bindgen_runtime::FromNapiValue, check_status, sys, NapiRaw};
+use crate::{bindgen_runtime::FromNapiValue, check_status, sys, JsObject, NapiRaw};
+
+pub type This = JsObject;
 
 pub struct ClassInstance<T: 'static> {
   pub value: sys::napi_value,

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

@@ -254,6 +254,7 @@ Generated by [AVA](https://avajs.dev).
       static newRaph(): NinjaTurtle␊
       getMaskColor(): string␊
       getName(): string␊
+      returnThis(this: this): this␊
     }␊
     export type JsAssets = Assets␊
     export class Assets {␊

examples/napi/__test__/values.spec.ts

@@ -21,6 +21,7 @@ import {
   getCwd,
   Animal,
   Kind,
+  NinjaTurtle,
   ClassWithFactory,
   CustomNumEnum,
   Context,
@@ -173,6 +174,8 @@ test('class', (t) => {
   t.is(dog.type, Kind.Cat)
   const assets = new Assets()
   t.is(assets.get(1)?.filePath, 1)
+  const turtle = NinjaTurtle.newRaph()
+  t.is(turtle.returnThis(), turtle)
 })
 
 test('class factory', (t) => {

examples/napi/index.d.ts

@@ -244,6 +244,7 @@ export class NinjaTurtle {
   static newRaph(): NinjaTurtle
   getMaskColor(): string
   getName(): string
+  returnThis(this: this): this
 }
 export type JsAssets = Assets
 export class Assets {

examples/napi/src/class.rs

@@ -1,5 +1,5 @@
 use napi::{
-  bindgen_prelude::{Buffer, ClassInstance},
+  bindgen_prelude::{Buffer, ClassInstance, This},
   Env, Result,
 };
 
@@ -229,6 +229,11 @@ impl NinjaTurtle {
   pub fn get_name(&self) -> &str {
     self.name.as_str()
   }
+
+  #[napi]
+  pub fn return_this(&self, this: This) -> This {
+    this
+  }
 }
 
 #[napi(js_name = "Assets")]