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[Merged by Bors] - Refactor guards into a ContextCleanupGuard abstraction #2890

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[Merged by Bors] - Refactor guards into a ContextCleanupGuard abstraction #2890

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28 changes: 9 additions & 19 deletions boa_engine/src/builtins/eval/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,20 +89,6 @@ impl Eval {
Restore(Vec<Environment>),
}

/// Restores the environment after calling `eval` or after throwing an error.
fn restore_environment(context: &mut Context<'_>, action: EnvStackAction) {
match action {
EnvStackAction::Truncate(size) => {
context.vm.environments.truncate(size);
}
EnvStackAction::Restore(envs) => {
// Pop all environments created during the eval execution and restore the original stack.
context.vm.environments.truncate(1);
context.vm.environments.extend(envs);
}
}
}

// 1. Assert: If direct is false, then strictCaller is also false.
debug_assert!(direct || !strict);

Expand Down Expand Up @@ -230,6 +216,14 @@ impl Eval {
EnvStackAction::Restore(environments)
};

let context = &mut context.guard(move |ctx| match action {
EnvStackAction::Truncate(len) => ctx.vm.environments.truncate(len),
EnvStackAction::Restore(envs) => {
ctx.vm.environments.truncate(1);
ctx.vm.environments.extend(envs);
}
});

// Only need to check on non-strict mode since strict mode automatically creates a function
// environment for all eval calls.
if !strict {
Expand All @@ -239,7 +233,6 @@ impl Eval {
.environments
.has_lex_binding_until_function_environment(&top_level_var_declared_names(&body))
{
restore_environment(context, action);
let name = context.interner().resolve_expect(name.sym());
let msg = format!("variable declaration {name} in eval function already exists as a lexical variable");
return Err(JsNativeError::syntax().with_message(msg).into());
Expand Down Expand Up @@ -267,10 +260,7 @@ impl Eval {
if direct && !strict {
context.vm.environments.extend_outer_function_environment();
}
let result = context.execute(code_block);

restore_environment(context, action);

result
context.execute(code_block)
}
}
64 changes: 63 additions & 1 deletion boa_engine/src/context/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -561,9 +561,17 @@ impl Context<'_> {
}
}

#[cfg(feature = "intl")]
impl<'host> Context<'host> {
/// Creates a `ContextCleanupGuard` that executes some cleanup after being dropped.
pub(crate) fn guard<F>(&mut self, cleanup: F) -> ContextCleanupGuard<'_, 'host, F>
where
F: FnOnce(&mut Context<'_>) + 'static,
{
ContextCleanupGuard::new(self, cleanup)
}

/// Get the ICU related utilities
#[cfg(feature = "intl")]
pub(crate) const fn icu(&self) -> &icu::Icu<'host> {
&self.icu
}
Expand Down Expand Up @@ -742,3 +750,57 @@ impl<'icu, 'hooks, 'queue> ContextBuilder<'icu, 'hooks, 'queue> {
Ok(context)
}
}

/// A cleanup guard for a [`Context`] that is executed when dropped.
#[derive(Debug)]
pub(crate) struct ContextCleanupGuard<'a, 'host, F>
where
F: FnOnce(&mut Context<'_>) + 'static,
{
context: &'a mut Context<'host>,
cleanup: Option<F>,
}

impl<'a, 'host, F> ContextCleanupGuard<'a, 'host, F>
where
F: FnOnce(&mut Context<'_>) + 'static,
{
/// Creates a new `ContextCleanupGuard` from the current context and its cleanup operation.
pub(crate) fn new(context: &'a mut Context<'host>, cleanup: F) -> Self {
Self {
context,
cleanup: Some(cleanup),
}
}
}

impl<'host, F> std::ops::Deref for ContextCleanupGuard<'_, 'host, F>
where
F: FnOnce(&mut Context<'_>) + 'static,
{
type Target = Context<'host>;

fn deref(&self) -> &Self::Target {
self.context
}
}

impl<F> std::ops::DerefMut for ContextCleanupGuard<'_, '_, F>
where
F: FnOnce(&mut Context<'_>) + 'static,
{
fn deref_mut(&mut self) -> &mut Self::Target {
self.context
}
}

impl<F> Drop for ContextCleanupGuard<'_, '_, F>
where
F: FnOnce(&mut Context<'_>) + 'static,
{
fn drop(&mut self) {
if let Some(cleanup) = self.cleanup.take() {
cleanup(self.context);
}
}
}
67 changes: 20 additions & 47 deletions boa_engine/src/vm/code_block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ use crate::{
error::JsNativeError,
object::{internal_methods::get_prototype_from_constructor, JsObject, ObjectData, PROTOTYPE},
property::PropertyDescriptor,
realm::Realm,
string::utf16,
vm::CallFrame,
Context, JsError, JsResult, JsString, JsValue,
Expand Down Expand Up @@ -846,63 +845,29 @@ pub(crate) fn create_generator_function_object(
constructor
}

struct ContextCleanupGuard<'a, 'host> {
context: &'a mut Context<'host>,
old_realm: Realm,
old_active_function: Option<JsObject>,
}

impl<'a, 'host> ContextCleanupGuard<'a, 'host> {
/// Creates a new guard that resets the realm of the context on exit.
fn new(context: &'a mut Context<'host>, realm: Realm, active_function: JsObject) -> Self {
let old_realm = context.enter_realm(realm);
let old_active_function = context.vm.active_function.replace(active_function);
Self {
context,
old_realm,
old_active_function,
}
}
}

impl Drop for ContextCleanupGuard<'_, '_> {
fn drop(&mut self) {
self.context.enter_realm(self.old_realm.clone());
std::mem::swap(
&mut self.context.vm.active_function,
&mut self.old_active_function,
);
}
}

impl<'host> std::ops::Deref for ContextCleanupGuard<'_, 'host> {
type Target = Context<'host>;

fn deref(&self) -> &Self::Target {
self.context
}
}

impl std::ops::DerefMut for ContextCleanupGuard<'_, '_> {
fn deref_mut(&mut self) -> &mut Self::Target {
self.context
}
}

impl JsObject {
pub(crate) fn call_internal(
&self,
this: &JsValue,
args: &[JsValue],
context: &mut Context<'_>,
) -> JsResult<JsValue> {
let old_realm = context.realm().clone();
let old_active_fn = context.vm.active_function.clone();

let context = &mut context.guard(move |ctx| {
ctx.enter_realm(old_realm);
ctx.vm.active_function = old_active_fn;
});

let this_function_object = self.clone();
let active_function = self.clone();
let object = self.borrow();
let function_object = object.as_function().expect("not a function");
let realm = function_object.realm().clone();

let context = &mut ContextCleanupGuard::new(context, realm, active_function);
context.enter_realm(realm);
context.vm.active_function = Some(active_function);

let (code, mut environments, class_object, async_, gen) = match function_object.kind() {
FunctionKind::Native {
Expand Down Expand Up @@ -941,7 +906,6 @@ impl JsObject {
false,
)
}

FunctionKind::Async {
code,
environments,
Expand Down Expand Up @@ -1182,13 +1146,22 @@ impl JsObject {
this_target: &JsValue,
context: &mut Context<'_>,
) -> JsResult<Self> {
let old_realm = context.realm().clone();
let old_active_fn = context.vm.active_function.clone();
let context = &mut context.guard(move |ctx| {
ctx.enter_realm(old_realm);
ctx.vm.active_function = old_active_fn;
});

let this_function_object = self.clone();
let active_function = self.clone();
let object = self.borrow();
let function_object = object.as_function().expect("not a function");
let realm = function_object.realm().clone();

let context = &mut ContextCleanupGuard::new(context, realm, active_function);
context.enter_realm(realm);
context.vm.active_function = Some(active_function);

match function_object.kind() {
FunctionKind::Native {
function,
Expand Down