Implement Error.isError (#4114)

core/engine/src/builtins/error/aggregate.rs

@@ -22,7 +22,7 @@ use crate::{
 };
 use boa_profiler::Profiler;
 
-use super::{Error, ErrorObject};
+use super::Error;
 
 #[derive(Debug, Clone, Copy)]
 pub(crate) struct AggregateError;
@@ -91,7 +91,7 @@ impl BuiltInConstructor for AggregateError {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Aggregate,
+            Error::Aggregate,
         );
 
         // 3. If message is not undefined, then

core/engine/src/builtins/error/eval.rs

@@ -23,7 +23,7 @@ use crate::{
 };
 use boa_profiler::Profiler;
 
-use super::{Error, ErrorObject};
+use super::Error;
 
 /// JavaScript `EvalError` implementation.
 #[derive(Debug, Clone, Copy)]
@@ -86,7 +86,7 @@ impl BuiltInConstructor for EvalError {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Eval,
+            Error::Eval,
         );
 
         // 3. If message is not undefined, then

core/engine/src/builtins/error/mod.rs

@@ -46,7 +46,7 @@ pub(crate) use self::uri::UriError;
 
 use super::{BuiltInBuilder, BuiltInConstructor, IntrinsicObject};
 
-/// A `NativeError` object, per the [ECMAScript spec][spec].
+/// A built-in `Error` object, per the [ECMAScript spec][spec].
 ///
 /// This is used internally to convert between [`JsObject`] and
 /// [`JsNativeError`] correctly, but it can also be used to manually create `Error`
@@ -61,7 +61,7 @@ use super::{BuiltInBuilder, BuiltInConstructor, IntrinsicObject};
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Trace, Finalize, JsData)]
 #[boa_gc(empty_trace)]
 #[non_exhaustive]
-pub enum ErrorObject {
+pub enum Error {
     /// The `AggregateError` object type.
     ///
     /// More information:
@@ -127,20 +127,20 @@ pub enum ErrorObject {
     Uri,
 }
 
-/// Built-in `Error` object.
-#[derive(Debug, Clone, Copy)]
-pub(crate) struct Error;
-
 impl IntrinsicObject for Error {
     fn init(realm: &Realm) {
         let _timer = Profiler::global().start_event(std::any::type_name::<Self>(), "init");
 
         let attribute = Attribute::WRITABLE | Attribute::NON_ENUMERABLE | Attribute::CONFIGURABLE;
-        BuiltInBuilder::from_standard_constructor::<Self>(realm)
+        let builder = BuiltInBuilder::from_standard_constructor::<Self>(realm)
             .property(js_string!("name"), Self::NAME, attribute)
             .property(js_string!("message"), js_string!(), attribute)
-            .method(Self::to_string, js_string!("toString"), 0)
-            .build();
+            .method(Self::to_string, js_string!("toString"), 0);
+
+        #[cfg(feature = "experimental")]
+        let builder = builder.static_method(Error::is_error, js_string!("isError"), 1);
+
+        builder.build();
     }
 
     fn get(intrinsics: &Intrinsics) -> JsObject {
@@ -162,7 +162,7 @@ impl BuiltInConstructor for Error {
 
     /// `Error( message [ , options ] )`
     ///
-    /// Create a new error object.
+    /// Creates a new error object.
     fn constructor(
         new_target: &JsValue,
         args: &[JsValue],
@@ -184,7 +184,7 @@ impl BuiltInConstructor for Error {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Error,
+            Error::Error,
         );
 
         // 3. If message is not undefined, then
@@ -280,4 +280,26 @@ impl Error {
         // the code unit 0x0020 (SPACE), and msg.
         Ok(js_string!(&name, js_str!(": "), &msg).into())
     }
+
+    /// [`Error.isError`][spec].
+    ///
+    /// Returns a boolean indicating whether the argument is a built-in Error instance or not.
+    ///
+    /// [spec]: https://tc39.es/proposal-is-error/#sec-error.iserror
+    #[cfg(feature = "experimental")]
+    #[allow(clippy::unnecessary_wraps)]
+    fn is_error(_: &JsValue, args: &[JsValue], _: &mut Context) -> JsResult<JsValue> {
+        // 1. Return IsError(arg).
+
+        // https://tc39.es/proposal-is-error/#sec-iserror
+
+        // 1. If argument is not an Object, return false.
+        // 2. If argument has an [[ErrorData]] internal slot, return true.
+        // 3. Return false.
+        Ok(args
+            .get_or_undefined(0)
+            .as_object()
+            .is_some_and(|o| o.is::<Self>())
+            .into())
+    }
 }

core/engine/src/builtins/error/range.rs

@@ -21,7 +21,7 @@ use crate::{
 };
 use boa_profiler::Profiler;
 
-use super::{Error, ErrorObject};
+use super::Error;
 
 /// JavaScript `RangeError` implementation.
 #[derive(Debug, Clone, Copy)]
@@ -84,7 +84,7 @@ impl BuiltInConstructor for RangeError {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Range,
+            Error::Range,
         );
 
         // 3. If message is not undefined, then

core/engine/src/builtins/error/reference.rs

@@ -21,7 +21,7 @@ use crate::{
 };
 use boa_profiler::Profiler;
 
-use super::{Error, ErrorObject};
+use super::Error;
 
 #[derive(Debug, Clone, Copy)]
 pub(crate) struct ReferenceError;
@@ -86,7 +86,7 @@ impl BuiltInConstructor for ReferenceError {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Reference,
+            Error::Reference,
         );
 
         // 3. If message is not undefined, then

core/engine/src/builtins/error/syntax.rs

@@ -23,7 +23,7 @@ use crate::{
 };
 use boa_profiler::Profiler;
 
-use super::{Error, ErrorObject};
+use super::Error;
 
 /// JavaScript `SyntaxError` implementation.
 #[derive(Debug, Clone, Copy)]
@@ -89,7 +89,7 @@ impl BuiltInConstructor for SyntaxError {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Syntax,
+            Error::Syntax,
         );
 
         // 3. If message is not undefined, then

core/engine/src/builtins/error/type.rs

@@ -29,7 +29,7 @@ use crate::{
 };
 use boa_profiler::Profiler;
 
-use super::{Error, ErrorObject};
+use super::Error;
 
 /// JavaScript `TypeError` implementation.
 #[derive(Debug, Clone, Copy)]
@@ -92,7 +92,7 @@ impl BuiltInConstructor for TypeError {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Type,
+            Error::Type,
         );
 
         // 3. If message is not undefined, then

core/engine/src/builtins/error/uri.rs

@@ -22,7 +22,7 @@ use crate::{
 };
 use boa_profiler::Profiler;
 
-use super::{Error, ErrorObject};
+use super::Error;
 
 /// JavaScript `URIError` implementation.
 #[derive(Debug, Clone, Copy)]
@@ -85,7 +85,7 @@ impl BuiltInConstructor for UriError {
         let o = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             prototype,
-            ErrorObject::Uri,
+            Error::Uri,
         );
 
         // 3. If message is not undefined, then

core/engine/src/builtins/object/mod.rs

@@ -14,7 +14,7 @@
 //! [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object
 
 use super::{
-    error::ErrorObject, Array, BuiltInBuilder, BuiltInConstructor, Date, IntrinsicObject, RegExp,
+    error::Error, Array, BuiltInBuilder, BuiltInConstructor, Date, IntrinsicObject, RegExp,
 };
 use crate::value::JsVariant;
 use crate::{
@@ -850,7 +850,7 @@ impl OrdinaryObject {
             } else if o.is_callable() {
                 // 7. Else if O has a [[Call]] internal method, let builtinTag be "Function".
                 js_str!("Function")
-            } else if o.is::<ErrorObject>() {
+            } else if o.is::<Error>() {
                 // 8. Else if O has an [[ErrorData]] internal slot, let builtinTag be "Error".
                 js_str!("Error")
             } else if o.is::<bool>() {

core/engine/src/error.rs

@@ -1,7 +1,7 @@
 //! Error-related types and conversions.
 
 use crate::{
-    builtins::{error::ErrorObject, Array},
+    builtins::{error::Error, Array},
     js_string,
     object::JsObject,
     property::PropertyDescriptor,
@@ -332,12 +332,12 @@ impl JsError {
     ///
     /// ```rust
     /// # use boa_engine::{Context, JsError, JsNativeError};
-    /// # use boa_engine::builtins::error::ErrorObject;
+    /// # use boa_engine::builtins::error::Error;
     /// let context = &mut Context::default();
     /// let error: JsError = JsNativeError::eval().with_message("invalid script").into();
     /// let error_val = error.to_opaque(context);
     ///
-    /// assert!(error_val.as_object().unwrap().is::<ErrorObject>());
+    /// assert!(error_val.as_object().unwrap().is::<Error>());
     /// ```
     pub fn to_opaque(&self, context: &mut Context) -> JsValue {
         match &self.inner {
@@ -392,7 +392,7 @@ impl JsError {
                     .as_object()
                     .ok_or_else(|| TryNativeError::NotAnErrorObject(val.clone()))?;
                 let error = *obj
-                    .downcast_ref::<ErrorObject>()
+                    .downcast_ref::<Error>()
                     .ok_or_else(|| TryNativeError::NotAnErrorObject(val.clone()))?;
 
                 let try_get_property = |key: JsString, name, context: &mut Context| {
@@ -420,14 +420,14 @@ impl JsError {
                 let cause = try_get_property(js_string!("cause"), "cause", context)?;
 
                 let kind = match error {
-                    ErrorObject::Error => JsNativeErrorKind::Error,
-                    ErrorObject::Eval => JsNativeErrorKind::Eval,
-                    ErrorObject::Type => JsNativeErrorKind::Type,
-                    ErrorObject::Range => JsNativeErrorKind::Range,
-                    ErrorObject::Reference => JsNativeErrorKind::Reference,
-                    ErrorObject::Syntax => JsNativeErrorKind::Syntax,
-                    ErrorObject::Uri => JsNativeErrorKind::Uri,
-                    ErrorObject::Aggregate => {
+                    Error::Error => JsNativeErrorKind::Error,
+                    Error::Eval => JsNativeErrorKind::Eval,
+                    Error::Type => JsNativeErrorKind::Type,
+                    Error::Range => JsNativeErrorKind::Range,
+                    Error::Reference => JsNativeErrorKind::Reference,
+                    Error::Syntax => JsNativeErrorKind::Syntax,
+                    Error::Uri => JsNativeErrorKind::Uri,
+                    Error::Aggregate => {
                         let errors = obj.get(js_string!("errors"), context).map_err(|e| {
                             TryNativeError::InaccessibleProperty {
                                 property: "errors",
@@ -1066,13 +1066,13 @@ impl JsNativeError {
     ///
     /// ```rust
     /// # use boa_engine::{Context, JsError, JsNativeError, js_string};
-    /// # use boa_engine::builtins::error::ErrorObject;
+    /// # use boa_engine::builtins::error::Error;
     /// let context = &mut Context::default();
     ///
     /// let error = JsNativeError::error().with_message("error!");
     /// let error_obj = error.to_opaque(context);
     ///
-    /// assert!(error_obj.is::<ErrorObject>());
+    /// assert!(error_obj.is::<Error>());
     /// assert_eq!(
     ///     error_obj.get(js_string!("message"), context).unwrap(),
     ///     js_string!("error!").into()
@@ -1095,24 +1095,18 @@ impl JsNativeError {
             |realm| realm.intrinsics().constructors(),
         );
         let (prototype, tag) = match kind {
-            JsNativeErrorKind::Aggregate(_) => (
-                constructors.aggregate_error().prototype(),
-                ErrorObject::Aggregate,
-            ),
-            JsNativeErrorKind::Error => (constructors.error().prototype(), ErrorObject::Error),
-            JsNativeErrorKind::Eval => (constructors.eval_error().prototype(), ErrorObject::Eval),
-            JsNativeErrorKind::Range => {
-                (constructors.range_error().prototype(), ErrorObject::Range)
+            JsNativeErrorKind::Aggregate(_) => {
+                (constructors.aggregate_error().prototype(), Error::Aggregate)
             }
-            JsNativeErrorKind::Reference => (
-                constructors.reference_error().prototype(),
-                ErrorObject::Reference,
-            ),
-            JsNativeErrorKind::Syntax => {
-                (constructors.syntax_error().prototype(), ErrorObject::Syntax)
+            JsNativeErrorKind::Error => (constructors.error().prototype(), Error::Error),
+            JsNativeErrorKind::Eval => (constructors.eval_error().prototype(), Error::Eval),
+            JsNativeErrorKind::Range => (constructors.range_error().prototype(), Error::Range),
+            JsNativeErrorKind::Reference => {
+                (constructors.reference_error().prototype(), Error::Reference)
             }
-            JsNativeErrorKind::Type => (constructors.type_error().prototype(), ErrorObject::Type),
-            JsNativeErrorKind::Uri => (constructors.uri_error().prototype(), ErrorObject::Uri),
+            JsNativeErrorKind::Syntax => (constructors.syntax_error().prototype(), Error::Syntax),
+            JsNativeErrorKind::Type => (constructors.type_error().prototype(), Error::Type),
+            JsNativeErrorKind::Uri => (constructors.uri_error().prototype(), Error::Uri),
             #[cfg(feature = "fuzz")]
             JsNativeErrorKind::NoInstructionsRemain => {
                 unreachable!(
@@ -1318,18 +1312,18 @@ impl JsNativeErrorKind {
     }
 }
 
-impl PartialEq<ErrorObject> for JsNativeErrorKind {
-    fn eq(&self, other: &ErrorObject) -> bool {
+impl PartialEq<Error> for JsNativeErrorKind {
+    fn eq(&self, other: &Error) -> bool {
         matches!(
             (self, other),
-            (Self::Aggregate(_), ErrorObject::Aggregate)
-                | (Self::Error, ErrorObject::Error)
-                | (Self::Eval, ErrorObject::Eval)
-                | (Self::Range, ErrorObject::Range)
-                | (Self::Reference, ErrorObject::Reference)
-                | (Self::Syntax, ErrorObject::Syntax)
-                | (Self::Type, ErrorObject::Type)
-                | (Self::Uri, ErrorObject::Uri)
+            (Self::Aggregate(_), Error::Aggregate)
+                | (Self::Error, Error::Error)
+                | (Self::Eval, Error::Eval)
+                | (Self::Range, Error::Range)
+                | (Self::Reference, Error::Reference)
+                | (Self::Syntax, Error::Syntax)
+                | (Self::Type, Error::Type)
+                | (Self::Uri, Error::Uri)
         )
     }
 }

core/engine/src/value/display.rs

@@ -1,7 +1,7 @@
 use super::{fmt, Display, HashSet, JsValue, JsVariant};
 use crate::{
     builtins::{
-        error::ErrorObject, map::ordered_map::OrderedMap, promise::PromiseState,
+        error::Error, map::ordered_map::OrderedMap, promise::PromiseState,
         set::ordered_set::OrderedSet, Array, Promise,
     },
     js_string,
@@ -191,7 +191,7 @@ pub(crate) fn log_string_from(x: &JsValue, print_internals: bool, print_children
                 } else {
                     format!("Set({size})")
                 }
-            } else if v_bor.is::<ErrorObject>() {
+            } else if v_bor.is::<Error>() {
                 drop(v_bor);
                 let name: Cow<'static, str> = v
                     .get_property(&js_string!("name").into())

core/runtime/src/lib.rs

@@ -150,7 +150,7 @@ pub(crate) mod test {
         },
         AssertNativeError {
             source: Cow<'static, str>,
-            kind: builtins::error::ErrorObject,
+            kind: builtins::error::Error,
             message: &'static str,
         },
         AssertContext {