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Implement Error.prototype.stack accessor property #4552

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Implement Error.prototype.stack accessor property #4552

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113 changes: 101 additions & 12 deletions core/engine/src/builtins/error/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ use crate::{
property::Attribute,
realm::Realm,
string::StaticJsStrings,
vm::shadow_stack::ShadowEntry,
vm::shadow_stack::ErrorLocation,
};
use boa_gc::{Finalize, Trace};
use boa_macros::js_str;
Expand Down Expand Up @@ -136,7 +136,7 @@ pub struct Error {

// The position of where the Error was created does not affect equality check.
#[unsafe_ignore_trace]
pub(crate) position: IgnoreEq<Option<ShadowEntry>>,
pub(crate) location: IgnoreEq<ErrorLocation>,
}

impl Error {
Expand All @@ -146,34 +146,53 @@ impl Error {
pub fn new(tag: ErrorKind) -> Self {
Self {
tag,
position: IgnoreEq(None),
location: IgnoreEq(ErrorLocation::Position(None)),
}
}

/// Create a new [`Error`] with the given optional [`ShadowEntry`].
pub(crate) fn with_shadow_entry(tag: ErrorKind, entry: Option<ShadowEntry>) -> Self {
/// Create a new [`Error`] with the given [`ErrorLocation`].
pub(crate) fn with_location(tag: ErrorKind, location: ErrorLocation) -> Self {
Self {
tag,
position: IgnoreEq(entry),
location: IgnoreEq(location),
}
}

/// Get the position from the last called function.
pub(crate) fn with_caller_position(tag: ErrorKind, context: &Context) -> Self {
let limit = context.runtime_limits().backtrace_limit();
let backtrace = context.vm.shadow_stack.caller_position(limit);
Self {
tag,
position: IgnoreEq(context.vm.shadow_stack.caller_position()),
location: IgnoreEq(ErrorLocation::Backtrace(backtrace)),
}
}
}

impl IntrinsicObject for Error {
fn init(realm: &Realm) {
let attribute = Attribute::WRITABLE | Attribute::NON_ENUMERABLE | Attribute::CONFIGURABLE;
let property_attribute =
Attribute::WRITABLE | Attribute::NON_ENUMERABLE | Attribute::CONFIGURABLE;
let accessor_attribute = Attribute::NON_ENUMERABLE | Attribute::CONFIGURABLE;

let get_stack = BuiltInBuilder::callable(realm, Self::get_stack)
.name(js_string!("get stack"))
.build();

let set_stack = BuiltInBuilder::callable(realm, Self::set_stack)
.name(js_string!("set stack"))
.build();

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);
.property(js_string!("name"), Self::NAME, property_attribute)
.property(js_string!("message"), js_string!(), property_attribute)
.method(Self::to_string, js_string!("toString"), 0)
.accessor(
js_string!("stack"),
Some(get_stack),
Some(set_stack),
accessor_attribute,
);

#[cfg(feature = "experimental")]
let builder = builder.static_method(Error::is_error, js_string!("isError"), 1);
Expand All @@ -192,7 +211,7 @@ impl BuiltInObject for Error {

impl BuiltInConstructor for Error {
const CONSTRUCTOR_ARGUMENTS: usize = 1;
const PROTOTYPE_STORAGE_SLOTS: usize = 3;
const PROTOTYPE_STORAGE_SLOTS: usize = 5;
const CONSTRUCTOR_STORAGE_SLOTS: usize = 1;

const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
Expand Down Expand Up @@ -263,6 +282,76 @@ impl Error {
Ok(())
}

/// `get Error.prototype.stack`
///
/// The accessor property of Error instances represents the stack trace
/// when the error was created.
///
/// More information:
/// - [Proposal][spec]
///
/// [spec]: https://tc39.es/proposal-error-stacks/
fn get_stack(this: &JsValue, _: &[JsValue], _context: &mut Context) -> JsResult<JsValue> {
// 1. Let E be the this value.
// 2. If E is not an Object, return undefined.
let Some(e) = this.as_object() else {
return Ok(JsValue::undefined());
};

// 3. Let errorData be the value of the [[ErrorData]] internal slot of E.
// 4. If errorData is undefined, return undefined.
let Some(error_data) = e.downcast_ref::<Error>() else {
return Ok(JsValue::undefined());
};

// 5. Let stackString be an implementation-defined String value representing the call stack.
// 6. Return stackString.
if let Some(backtrace) = error_data.location.0.backtrace() {
let stack_string = backtrace
.iter()
.rev()
.map(|entry| format!(" at {}\n", entry.display(true)))
.collect::<String>();
return Ok(js_string!(stack_string).into());
}

// 7. If no stack trace is available, return undefined.
Ok(JsValue::undefined())
}

/// `set Error.prototype.stack`
///
/// The setter for the stack property.
///
/// More information:
/// - [Proposal][spec]
///
/// [spec]: https://tc39.es/proposal-error-stacks/
fn set_stack(this: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
// 1. Let E be the this value.
// 2. If Type(E) is not Object, throw a TypeError exception.
let e = this.as_object().ok_or_else(|| {
JsNativeError::typ()
.with_message("Error.prototype.stack setter requires that 'this' be an Object")
})?;

// 3. Let numberOfArgs be the number of arguments passed to this function call.
let number_of_args = args.len();

// 4. If numberOfArgs is 0, throw a TypeError exception.
if number_of_args == 0 {
return Err(JsNativeError::typ()
.with_message(
"Error.prototype.stack setter requires at least 1 argument, but only 0 were passed",
)
.into());
}

// 5. Return ? CreateDataPropertyOrThrow(E, "stack", value).
e.create_data_property_or_throw(js_string!("stack"), args[0].clone(), context)
.map(Into::into)
}

/// `Error.prototype.toString()`
///
/// The `toString()` method returns a string representing the specified Error object.
Expand Down
78 changes: 14 additions & 64 deletions core/engine/src/error.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,15 +12,11 @@ use crate::{
realm::Realm,
vm::{
NativeSourceInfo,
shadow_stack::{Backtrace, ShadowEntry},
shadow_stack::{Backtrace as ShadowBacktrace, ErrorLocation, ShadowEntry},
},
};
use boa_gc::{Finalize, Trace, custom_trace};
use std::{
borrow::Cow,
error,
fmt::{self},
};
use std::{borrow::Cow, error, fmt};
use thiserror::Error;

/// Create an error object from a value or string literal. Optionally the
Expand Down Expand Up @@ -209,7 +205,8 @@ macro_rules! js_error {
pub struct JsError {
inner: Repr,

pub(crate) backtrace: Option<Backtrace>,
#[unsafe_ignore_trace]
pub(crate) backtrace: Option<ShadowBacktrace>,
}

impl Eq for JsError {}
Expand Down Expand Up @@ -503,7 +500,7 @@ impl JsError {

let cause = try_get_property(js_string!("cause"), "cause", context)?;

let position = error_data.position.clone();
let location = error_data.location.clone();
let kind = match error_data.tag {
ErrorKind::Error => JsNativeErrorKind::Error,
ErrorKind::Eval => JsNativeErrorKind::Eval,
Expand Down Expand Up @@ -558,7 +555,7 @@ impl JsError {
message,
cause: cause.map(|v| Box::new(Self::from_opaque(v))),
realm: Some(realm),
position,
location,
})
}
}
Expand Down Expand Up @@ -764,54 +761,7 @@ impl fmt::Display for JsError {

if let Some(shadow_stack) = &self.backtrace {
for entry in shadow_stack.iter().rev() {
write!(f, "\n at ")?;
match entry {
ShadowEntry::Native {
function_name,
source_info,
} => {
if let Some(function_name) = function_name {
write!(f, "{}", function_name.to_std_string_escaped())?;
} else {
f.write_str("<anonymous>")?;
}

if let Some(loc) = source_info.as_location() {
write!(
f,
" (native at {}:{}:{})",
loc.file(),
loc.line(),
loc.column()
)?;
} else {
f.write_str(" (native)")?;
}
}
ShadowEntry::Bytecode { pc, source_info } => {
let has_function_name = !source_info.function_name().is_empty();
if has_function_name {
write!(f, "{}", source_info.function_name().to_std_string_escaped(),)?;
} else {
f.write_str("<anonymous>")?;
}

f.write_str(" (")?;
source_info.map().path().fmt(f)?;

if let Some(position) = source_info.map().find(*pc) {
write!(
f,
":{}:{}",
position.line_number(),
position.column_number()
)?;
} else {
f.write_str(":?:?")?;
}
f.write_str(")")?;
}
}
write!(f, "\n at {}", entry.display(true))?;
}
}
Ok(())
Expand Down Expand Up @@ -871,7 +821,7 @@ pub struct JsNativeError {
#[source]
cause: Option<Box<JsError>>,
realm: Option<Realm>,
position: IgnoreEq<Option<ShadowEntry>>,
location: IgnoreEq<ErrorLocation>,
}

impl fmt::Display for JsNativeError {
Expand All @@ -883,8 +833,8 @@ impl fmt::Display for JsNativeError {
write!(f, ": {message}")?;
}

if let Some(position) = &self.position.0 {
position.fmt(f)?;
if let Some(entry) = self.location.0.position() {
write!(f, "{}", entry.display(false))?;
}

Ok(())
Expand Down Expand Up @@ -945,10 +895,10 @@ impl JsNativeError {
message,
cause,
realm: None,
position: IgnoreEq(Some(ShadowEntry::Native {
location: IgnoreEq(ErrorLocation::Position(Some(ShadowEntry::Native {
function_name: None,
source_info: NativeSourceInfo::caller(),
})),
}))),
}
}

Expand Down Expand Up @@ -1271,7 +1221,7 @@ impl JsNativeError {
message,
cause,
realm,
position,
location,
} = self;
let constructors = realm.as_ref().map_or_else(
|| context.intrinsics().constructors(),
Expand Down Expand Up @@ -1299,7 +1249,7 @@ impl JsNativeError {
let o = JsObject::from_proto_and_data_with_shared_shape(
context.root_shape(),
prototype,
Error::with_shadow_entry(tag, position.0.clone()),
Error::with_location(tag, location.0.clone()),
)
.upcast();

Expand Down
4 changes: 2 additions & 2 deletions core/engine/src/value/display.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -257,8 +257,8 @@ pub(crate) fn log_value_to(
.downcast_ref::<Error>()
.expect("already checked object type");

if let Some(position) = &data.position.0 {
write!(f, "{position}")?;
if let Some(entry) = data.location.0.position() {
write!(f, "{}", entry.display(false))?;
}
Ok(())
} else if let Some(promise) = v.downcast_ref::<Promise>() {
Expand Down
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