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LibJS: Implement await properly for async functions

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Fixes #20275

```
Summary:
    Diff Tests:
        +4 ✅    -4 ❌   

Diff Tests:
    test/built-ins/Array/fromAsync/non-iterable-input-with-thenable
    -async-mapped-awaits-callback-result-once.js ❌ -> ✅
    test/language/expressions/await/async-await-interleaved.js ❌ -> ✅
    test/language/expressions/await/await-awaits-thenables-that-
    throw.js ❌ -> ✅
    test/language/expressions/await/await-awaits-thenables.js ❌ -> ✅
```
This commit is contained in:
Luke Wilde 2023-08-09 22:12:07 +01:00 • committed by Andreas Kling
parent 5003b1a421
commit ae7a0c43a9
Notes: sideshowbarker 2024-07-16 20:21:48 +09:00
5 changed files with 175 additions and 69 deletions
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33
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
View file

@ -1582,12 +1582,39 @@ Bytecode::CodeGenerationErrorOr<void> CallExpression::generate_bytecode(Bytecode
return {};
}
static void generate_await(Bytecode::Generator& generator, Bytecode::Register received_completion_register, Bytecode::Register received_completion_type_register, Bytecode::Register received_completion_value_register, Bytecode::IdentifierTableIndex type_identifier, Bytecode::IdentifierTableIndex value_identifier);
// https://tc39.es/ecma262/#sec-return-statement-runtime-semantics-evaluation
Bytecode::CodeGenerationErrorOr<void> ReturnStatement::generate_bytecode(Bytecode::Generator& generator) const
{
if (m_argument)
if (m_argument) {
// ReturnStatement : return Expression ;
// 1. Let exprRef be ? Evaluation of Expression.
// 2. Let exprValue be ? GetValue(exprRef).
TRY(m_argument->generate_bytecode(generator));
else
// 3. If GetGeneratorKind() is async, set exprValue to ? Await(exprValue).
// Spec Issue?: The spec doesn't seem to do implicit await on explicit return for async functions, but does for
// async generators. However, the major engines do so, and this is observable via constructor lookups
// on Promise objects and custom thenables.
// See: https://tc39.es/ecma262/#sec-asyncblockstart
// c. Assert: If we return here, the async function either threw an exception or performed an implicit or explicit return; all awaiting is done.
if (generator.is_in_async_function()) {
auto received_completion_register = generator.allocate_register();
auto received_completion_type_register = generator.allocate_register();
auto received_completion_value_register = generator.allocate_register();
auto type_identifier = generator.intern_identifier("type");
auto value_identifier = generator.intern_identifier("value");
generate_await(generator, received_completion_register, received_completion_type_register, received_completion_value_register, type_identifier, value_identifier);
}
// 4. Return Completion Record { [[Type]]: return, [[Value]]: exprValue, [[Target]]: empty }.
} else {
// ReturnStatement : return ;
// 1. Return Completion Record { [[Type]]: return, [[Value]]: undefined, [[Target]]: empty }.
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
}
if (generator.is_in_generator_or_async_function()) {
generator.perform_needed_unwinds<Bytecode::Op::Yield>();
@ -1613,8 +1640,6 @@ static void get_received_completion_type_and_value(Bytecode::Generator& generato
generator.emit<Bytecode::Op::Store>(received_completion_value_register);
}
static void generate_await(Bytecode::Generator& generator, Bytecode::Register received_completion_register, Bytecode::Register received_completion_type_register, Bytecode::Register received_completion_value_register, Bytecode::IdentifierTableIndex type_identifier, Bytecode::IdentifierTableIndex value_identifier);
enum class AwaitBeforeYield {
No,
Yes,