`TryIntoJs` trait and derive macro for it (#3999)

* #3874: `TryIntoJs` impl for primitive types

* #3874: `#[derive(TryIntoJs)]`

is it ok to use `create_data_property_or_throw`?
in other words, am I create an object correctly?

* #3874: some (but not enough) tests

* #3874: fix `TryintoJs` derive bug in multi attr case

* #3874: `TryIntoJs` derive macro example

* fix paths in derive macro

* make lint happy

core/engine/src/value/conversions/mod.rs

@@ -7,6 +7,7 @@ use super::{JsBigInt, JsObject, JsString, JsSymbol, JsValue, Profiler};
 mod either;
 mod serde_json;
 pub(super) mod try_from_js;
+pub(super) mod try_into_js;
 
 pub(super) mod convert;
 

core/engine/src/value/conversions/try_into_js.rs

@@ -0,0 +1,289 @@
+use crate::{Context, JsNativeError, JsResult, JsValue};
+use boa_string::JsString;
+
+/// This trait adds a conversions from a Rust Type into [`JsValue`].
+pub trait TryIntoJs: Sized {
+    /// This function tries to convert a `Self` into [`JsValue`].
+    fn try_into_js(&self, context: &mut Context) -> JsResult<JsValue>;
+}
+
+impl TryIntoJs for bool {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        JsResult::Ok(JsValue::Boolean(*self))
+    }
+}
+
+impl TryIntoJs for &str {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        JsResult::Ok(JsValue::String(JsString::from(*self)))
+    }
+}
+impl TryIntoJs for String {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        JsResult::Ok(JsValue::String(JsString::from(self.as_str())))
+    }
+}
+
+macro_rules! impl_try_into_js_by_from {
+    ($t:ty) => {
+        impl TryIntoJs for $t {
+            fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+                JsResult::Ok(JsValue::from(self.clone()))
+            }
+        }
+    };
+    [$($ts:ty),+] => {
+        $(impl_try_into_js_by_from!($ts);)+
+    }
+}
+impl_try_into_js_by_from![i8, u8, i16, u16, i32, u32, f32, f64];
+impl_try_into_js_by_from![
+    JsValue,
+    JsString,
+    crate::JsBigInt,
+    crate::JsObject,
+    crate::JsSymbol,
+    crate::object::JsArray,
+    crate::object::JsArrayBuffer,
+    crate::object::JsDataView,
+    crate::object::JsDate,
+    crate::object::JsFunction,
+    crate::object::JsGenerator,
+    crate::object::JsMapIterator,
+    crate::object::JsMap,
+    crate::object::JsSetIterator,
+    crate::object::JsSet,
+    crate::object::JsSharedArrayBuffer,
+    crate::object::JsInt8Array,
+    crate::object::JsInt16Array,
+    crate::object::JsInt32Array,
+    crate::object::JsUint8Array,
+    crate::object::JsUint16Array,
+    crate::object::JsUint32Array,
+    crate::object::JsFloat32Array,
+    crate::object::JsFloat64Array
+];
+
+const MAX_SAFE_INTEGER_I64: i64 = (1 << 53) - 1;
+const MIN_SAFE_INTEGER_I64: i64 = -MAX_SAFE_INTEGER_I64;
+
+fn err_outside_safe_range() -> crate::JsError {
+    JsNativeError::typ()
+        .with_message("cannot convert value into JsValue: the value is outside the safe range")
+        .into()
+}
+fn convert_safe_i64(value: i64) -> JsValue {
+    i32::try_from(value).map_or(JsValue::Rational(value as f64), JsValue::Integer)
+}
+
+impl TryIntoJs for i64 {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        let value = *self;
+        #[allow(clippy::manual_range_contains)]
+        if value < MIN_SAFE_INTEGER_I64 || MAX_SAFE_INTEGER_I64 < value {
+            JsResult::Err(err_outside_safe_range())
+        } else {
+            JsResult::Ok(convert_safe_i64(value))
+        }
+    }
+}
+impl TryIntoJs for u64 {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        let value = *self;
+        if (MAX_SAFE_INTEGER_I64 as u64) < value {
+            JsResult::Err(err_outside_safe_range())
+        } else {
+            JsResult::Ok(convert_safe_i64(value as i64))
+        }
+    }
+}
+impl TryIntoJs for i128 {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        let value = *self;
+        if value < i128::from(MIN_SAFE_INTEGER_I64) || i128::from(MAX_SAFE_INTEGER_I64) < value {
+            JsResult::Err(err_outside_safe_range())
+        } else {
+            JsResult::Ok(convert_safe_i64(value as i64))
+        }
+    }
+}
+impl TryIntoJs for u128 {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        let value = *self;
+        if (MAX_SAFE_INTEGER_I64 as u128) < value {
+            JsResult::Err(err_outside_safe_range())
+        } else {
+            JsResult::Ok(convert_safe_i64(value as i64))
+        }
+    }
+}
+
+impl<T> TryIntoJs for Option<T>
+where
+    T: TryIntoJs,
+{
+    fn try_into_js(&self, context: &mut Context) -> JsResult<JsValue> {
+        match self {
+            Some(x) => x.try_into_js(context),
+            None => JsResult::Ok(JsValue::Null),
+        }
+    }
+}
+
+impl<T> TryIntoJs for Vec<T>
+where
+    T: TryIntoJs,
+{
+    fn try_into_js(&self, context: &mut Context) -> JsResult<JsValue> {
+        let arr = crate::object::JsArray::new(context);
+        for value in self {
+            let value = value.try_into_js(context)?;
+            arr.push(value, context)?;
+        }
+        JsResult::Ok(arr.into())
+    }
+}
+
+macro_rules! impl_try_into_js_for_tuples {
+    ($($names:ident : $ts:ident),+) => {
+        impl<$($ts: TryIntoJs,)+> TryIntoJs for ($($ts,)+) {
+            fn try_into_js(&self, context: &mut Context) -> JsResult<JsValue> {
+                let ($($names,)+) = self;
+                let arr = crate::object::JsArray::new(context);
+                $(arr.push($names.try_into_js(context)?, context)?;)+
+                JsResult::Ok(arr.into())
+            }
+        }
+    };
+}
+
+impl_try_into_js_for_tuples!(a: A);
+impl_try_into_js_for_tuples!(a: A, b: B);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D, e: E);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D, e: E, f: F);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D, e: E, f: F, g: G);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J);
+impl_try_into_js_for_tuples!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K);
+
+impl TryIntoJs for () {
+    fn try_into_js(&self, _context: &mut Context) -> JsResult<JsValue> {
+        JsResult::Ok(JsValue::Null)
+    }
+}
+
+impl<T, S> TryIntoJs for std::collections::HashSet<T, S>
+where
+    T: TryIntoJs,
+{
+    fn try_into_js(&self, context: &mut Context) -> JsResult<JsValue> {
+        let set = crate::object::JsSet::new(context);
+        for value in self {
+            let value = value.try_into_js(context)?;
+            set.add(value, context)?;
+        }
+        JsResult::Ok(set.into())
+    }
+}
+
+impl<K, V, S> TryIntoJs for std::collections::HashMap<K, V, S>
+where
+    K: TryIntoJs,
+    V: TryIntoJs,
+{
+    fn try_into_js(&self, context: &mut Context) -> JsResult<JsValue> {
+        let map = crate::object::JsMap::new(context);
+        for (key, value) in self {
+            let key = key.try_into_js(context)?;
+            let value = value.try_into_js(context)?;
+            map.set(key, value, context)?;
+        }
+        JsResult::Ok(map.into())
+    }
+}
+
+#[cfg(test)]
+mod try_into_js_tests {
+    use crate::value::{TryFromJs, TryIntoJs};
+    use crate::{Context, JsResult};
+
+    #[test]
+    fn big_int_err() {
+        fn assert<T: TryIntoJs>(int: &T, context: &mut Context) {
+            let expect_err = int.try_into_js(context);
+            assert!(expect_err.is_err());
+        }
+
+        let mut context = Context::default();
+        let context = &mut context;
+
+        let int = (1 << 55) + 17i64;
+        assert(&int, context);
+
+        let int = (1 << 55) + 17u64;
+        assert(&int, context);
+
+        let int = (1 << 55) + 17u128;
+        assert(&int, context);
+
+        let int = (1 << 55) + 17i128;
+        assert(&int, context);
+    }
+
+    #[test]
+    fn int_tuple() -> JsResult<()> {
+        let mut context = Context::default();
+        let context = &mut context;
+
+        let tuple_initial = (
+            -42i8,
+            42u8,
+            1764i16,
+            7641u16,
+            -((1 << 27) + 13),
+            (1 << 27) + 72u32,
+            (1 << 49) + 1793i64,
+            (1 << 49) + 1793u64,
+            -((1 << 49) + 7193i128),
+            (1 << 49) + 9173u128,
+        );
+
+        // it will rewrite without reading, so it's just for auto type resolving.
+        #[allow(unused_assignments)]
+        let mut tuple_after_transform = tuple_initial;
+
+        let js_value = tuple_initial.try_into_js(context)?;
+        tuple_after_transform = TryFromJs::try_from_js(&js_value, context)?;
+
+        assert_eq!(tuple_initial, tuple_after_transform);
+        Ok(())
+    }
+
+    #[test]
+    fn string() -> JsResult<()> {
+        let mut context = Context::default();
+        let context = &mut context;
+
+        let s_init = "String".to_string();
+        let js_value = s_init.try_into_js(context)?;
+        let s: String = TryFromJs::try_from_js(&js_value, context)?;
+        assert_eq!(s_init, s);
+        Ok(())
+    }
+
+    #[test]
+    fn vec() -> JsResult<()> {
+        let mut context = Context::default();
+        let context = &mut context;
+
+        let vec_init = vec![(-4i64, 2u64), (15, 15), (32, 23)];
+        let js_value = vec_init.try_into_js(context)?;
+        println!("JsValue: {}", js_value.display());
+        let vec: Vec<(i64, u64)> = TryFromJs::try_from_js(&js_value, context)?;
+        assert_eq!(vec_init, vec);
+        Ok(())
+    }
+}

core/engine/src/value/mod.rs

@@ -17,6 +17,7 @@ use once_cell::sync::Lazy;
 use boa_gc::{custom_trace, Finalize, Trace};
 #[doc(inline)]
 pub use boa_macros::TryFromJs;
+pub use boa_macros::TryIntoJs;
 use boa_profiler::Profiler;
 #[doc(inline)]
 pub use conversions::convert::Convert;
@@ -24,8 +25,8 @@ pub use conversions::convert::Convert;
 pub(crate) use self::conversions::IntoOrUndefined;
 #[doc(inline)]
 pub use self::{
-    conversions::try_from_js::TryFromJs, display::ValueDisplay, integer::IntegerOrInfinity,
-    operations::*, r#type::Type,
+    conversions::try_from_js::TryFromJs, conversions::try_into_js::TryIntoJs,
+    display::ValueDisplay, integer::IntegerOrInfinity, operations::*, r#type::Type,
 };
 use crate::builtins::RegExp;
 use crate::object::{JsFunction, JsPromise, JsRegExp};

core/macros/src/lib.rs

@@ -497,3 +497,110 @@ fn to_compile_errors(errors: Vec<syn::Error>) -> proc_macro2::TokenStream {
     let compile_errors = errors.iter().map(syn::Error::to_compile_error);
     quote!(#(#compile_errors)*)
 }
+
+/// Derives the `TryIntoJs` trait, with the `#[boa()]` attribute.
+///
+/// # Panics
+///
+/// It will panic if the user tries to derive the `TryIntoJs` trait in an `enum` or a tuple struct.
+#[proc_macro_derive(TryIntoJs, attributes(boa))]
+pub fn derive_try_into_js(input: TokenStream) -> TokenStream {
+    // Parse the input tokens into a syntax tree
+    let input = parse_macro_input!(input as DeriveInput);
+
+    let Data::Struct(data) = input.data else {
+        panic!("you can only derive TryFromJs for structs");
+    };
+    // TODO: Enums ?
+
+    let Fields::Named(fields) = data.fields else {
+        panic!("you can only derive TryFromJs for named-field structs")
+    };
+
+    let props = generate_obj_properties(fields)
+        .map_err(|err| vec![err])
+        .unwrap_or_else(to_compile_errors);
+
+    let type_name = input.ident;
+
+    // Build the output, possibly using quasi-quotation
+    let expanded = quote! {
+        impl ::boa_engine::value::TryIntoJs for #type_name {
+            fn try_into_js(&self, context: &mut boa_engine::Context) -> boa_engine::JsResult<boa_engine::JsValue> {
+                let obj = boa_engine::JsObject::default();
+                #props
+                boa_engine::JsResult::Ok(obj.into())
+            }
+        }
+    };
+
+    // Hand the output tokens back to the compiler
+    expanded.into()
+}
+
+/// Generates property creation for object.
+fn generate_obj_properties(fields: FieldsNamed) -> Result<proc_macro2::TokenStream, syn::Error> {
+    use syn::spanned::Spanned;
+
+    let mut prop_ctors = Vec::with_capacity(fields.named.len());
+
+    for field in fields.named {
+        let span = field.span();
+        let name = field.ident.ok_or_else(|| {
+            syn::Error::new(
+                span,
+                "you can only derive `TryIntoJs` for named-field structs",
+            )
+        })?;
+
+        let mut into_js_with = None;
+        let mut prop_key = format!("{name}");
+        let mut skip = false;
+
+        for attr in field
+            .attrs
+            .into_iter()
+            .filter(|attr| attr.path().is_ident("boa"))
+        {
+            attr.parse_nested_meta(|meta| {
+                if meta.path.is_ident("into_js_with") {
+                    let value = meta.value()?;
+                    into_js_with = Some(value.parse::<LitStr>()?);
+                    Ok(())
+                } else if meta.path.is_ident("rename") {
+                    let value = meta.value()?;
+                    prop_key = value.parse::<LitStr>()?.value();
+                    Ok(())
+                } else if meta.path.is_ident("skip") & meta.input.is_empty() {
+                    skip = true;
+                    Ok(())
+                } else {
+                    Err(meta.error(
+                        "invalid syntax in the `#[boa()]` attribute. \
+                              Note that this attribute only accepts the following syntax: \
+                            \n* `#[boa(into_js_with = \"fully::qualified::path\")]`\
+                            \n* `#[boa(rename = \"jsPropertyName\")]` \
+                            \n* `#[boa(skip)]` \
+                            ",
+                    ))
+                }
+            })?;
+        }
+
+        if skip {
+            continue;
+        }
+
+        let value = if let Some(into_js_with) = into_js_with {
+            let into_js_with = Ident::new(&into_js_with.value(), into_js_with.span());
+            quote! { #into_js_with(&self.#name, context)? }
+        } else {
+            quote! { boa_engine::value::TryIntoJs::try_into_js(&self.#name, context)? }
+        };
+        prop_ctors.push(quote! {
+            obj.create_data_property_or_throw(boa_engine::js_str!(#prop_key), #value, context)?;
+        });
+    }
+
+    Ok(quote! { #(#prop_ctors)* })
+}

examples/src/bin/try_into_js_derive.rs

@@ -0,0 +1,96 @@
+use boa_engine::{
+    js_string,
+    value::{TryFromJs, TryIntoJs},
+    Context, JsResult, JsValue, Source,
+};
+
+#[derive(TryIntoJs)]
+struct Test {
+    x: i32,
+    #[boa(rename = "y")]
+    y_point: i32,
+    #[allow(unused)]
+    #[boa(skip)]
+    tuple: (i32, u8, String),
+    #[boa(rename = "isReadable")]
+    #[boa(into_js_with = "readable_into_js")]
+    is_readable: i8,
+}
+
+#[derive(TryFromJs, Debug, PartialEq, Eq)]
+struct ResultVerifier {
+    x: i32,
+    y: i32,
+    #[boa(rename = "isReadable")]
+    is_readable: bool,
+}
+
+fn main() -> JsResult<()> {
+    let js_code = r#"
+    function pointShift(pointA, pointB) {
+        if (pointA.isReadable === true && pointB.isReadable === true) {
+            return {
+                x: pointA.x + pointB.x,
+                y: pointA.y + pointB.y,
+                isReadable: true,
+            }
+        }
+        return undefined
+    }
+    "#;
+
+    let mut context = Context::default();
+    let context = &mut context;
+
+    context.eval(Source::from_bytes(js_code))?;
+
+    let point_shift = context
+        .global_object()
+        .get(js_string!("pointShift"), context)?;
+    let point_shift = point_shift.as_callable().unwrap();
+
+    let a = Test {
+        x: 10,
+        y_point: 20,
+        tuple: (30, 40, "no matter".into()),
+        is_readable: 1,
+    };
+    let b = Test {
+        x: 2,
+        y_point: 1,
+        tuple: (30, 40, "no matter".into()),
+        is_readable: 2,
+    };
+    let c = Test {
+        x: 2,
+        y_point: 1,
+        tuple: (30, 40, "no matter".into()),
+        is_readable: 0,
+    };
+
+    let result = point_shift.call(
+        &JsValue::Undefined,
+        &[a.try_into_js(context)?, b.try_into_js(context)?],
+        context,
+    )?;
+    let verifier = ResultVerifier::try_from_js(&result, context)?;
+    let expect = ResultVerifier {
+        x: 10 + 2,
+        y: 20 + 1,
+        is_readable: true,
+    };
+    assert_eq!(verifier, expect);
+
+    let result = point_shift.call(
+        &JsValue::Undefined,
+        &[a.try_into_js(context)?, c.try_into_js(context)?],
+        context,
+    )?;
+    assert!(result.is_undefined());
+
+    Ok(())
+}
+
+fn readable_into_js(value: &i8, _context: &mut Context) -> JsResult<JsValue> {
+    Ok(JsValue::Boolean(*value != 0))
+}