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LibWeb/Bindings: Reuse @@iterator method for sequence union conversion

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When converting an object to a union containing a sequence, Web IDL
first gets @@iterator to decide whether the sequence arm applies, then
creates the sequence from the iterable using that same method.

The generator instead called sequence_to_idl_value(), which repeated the
@@iterator lookup. Split out create_sequence_from_iterable() and use it
from union sequence/FrozenArray conversion so overridden Symbol.iterator
accessors are only observed once.
This commit is contained in:
Shannon Booth 2026-06-09 20:03:03 +02:00 committed by Jelle Raaijmakers
parent d33525be65
commit 6c2ad3af02
2 changed files with 32 additions and 19 deletions
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46
Meta/Generators/libweb_bindings/to_idl_value.py
View file

@ -743,12 +743,6 @@ def sequence_to_idl_value(
includes: GeneratedIncludes,
context: GenerationContext,
) -> str:
includes.add("LibJS/Runtime/Error.h")
includes.add("LibJS/Runtime/Iterator.h")
includes.add("LibJS/Runtime/Value.h")
includes.add("LibJS/Runtime/ValueInlines.h")
includes.add("LibWeb/Bindings/ExceptionOrUtils.h")
element_type = sequence_type.parameters[0]
element_cpp_type = cpp_type_for_idl_type_details(element_type, context)
storage_type_name = element_cpp_type.contained_storage_type.value
@ -761,13 +755,37 @@ def sequence_to_idl_value(
if (!{value_name}.is_object())
return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAnObject, {value_name});
auto iterator_method0 = TRY({value_name}.get_method(vm, vm.well_known_symbol_iterator()));
if (!iterator_method0)
auto method = TRY({value_name}.get_method(vm, vm.well_known_symbol_iterator()));
if (!method)
return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotIterable, {value_name});
return TRY({create_sequence_from_iterable(sequence_type, identifier, value_name, "method", includes, context)});
}}()"""
# 3.2.21.1. Creating a sequence from an iterable, https://webidl.spec.whatwg.org/#create-sequence-from-iterable
def create_sequence_from_iterable(
sequence_type: IDLParameterizedType,
identifier: str,
value_name: str,
iterator_method_name: str,
includes: GeneratedIncludes,
context: GenerationContext,
) -> str:
includes.add("LibJS/Runtime/Error.h")
includes.add("LibJS/Runtime/Iterator.h")
includes.add("LibJS/Runtime/Value.h")
includes.add("LibJS/Runtime/ValueInlines.h")
includes.add("LibWeb/Bindings/ExceptionOrUtils.h")
element_type = sequence_type.parameters[0]
element_cpp_type = cpp_type_for_idl_type_details(element_type, context)
storage_type_name = element_cpp_type.contained_storage_type.value
return f"""[&]() -> JS::ThrowCompletionOr<{storage_type_name}<{element_cpp_type.name}>> {{
// To create an IDL value of type sequence<T> given an iterable iterable and an iterator getter method, perform the following steps:
// 1. Let iteratorRecord be ? GetIteratorFromMethod(iterable, method).
auto iterator0 = TRY(JS::get_iterator_from_method(vm, {value_name}, *iterator_method0));
auto iterator = TRY(JS::get_iterator_from_method(vm, {value_name}, *{iterator_method_name}));
{storage_type_name}<{element_cpp_type.name}> sequence;
@ -775,7 +793,7 @@ def sequence_to_idl_value(
// 3. Repeat
for (;;) {{
// 1. Let next be ? IteratorStepValue(iteratorRecord).
auto next = TRY(JS::iterator_step_value(vm, iterator0));
auto next = TRY(JS::iterator_step_value(vm, iterator));
// 2. If next is done, then return an IDL sequence value of type sequence<T> of length i, where the value of the element at index j is Sj.
if (!next.has_value())
@ -1045,30 +1063,26 @@ def union_to_idl_value(
# FIXME: 11.1 If types includes an async sequence type, then
# 11.2. If types includes a sequence type, then
if types.sequence_type is not None:
sequence_conversion = sequence_to_idl_value(types.sequence_type, identifier, value_name, includes, context)
append(f"""
// 1. Let method be ? GetMethod(V, @@iterator).
auto method = TRY({value_name}.get_method(vm, vm.well_known_symbol_iterator()));
// 2. If method is not undefined, return the result of creating a sequence of that type from V and method.
if (method) {{
auto sequence_union_type = TRY({sequence_conversion});
auto sequence_union_type = TRY({create_sequence_from_iterable(types.sequence_type, identifier, value_name, "method", includes, context)});
return {variant_type} {{ sequence_union_type }};
}}
""")
# 11.3. If types includes a frozen array type, then
if types.frozen_array_type is not None:
frozen_array_conversion = sequence_to_idl_value(
types.frozen_array_type, identifier, value_name, includes, context
)
append(f"""
// 1. Let method be ? GetMethod(V, @@iterator).
auto frozen_array_method = TRY({value_name}.get_method(vm, vm.well_known_symbol_iterator()));
// 2. If method is not undefined, return the result of creating a frozen array of that type from V and method.
if (frozen_array_method) {{
auto frozen_array_union_type = TRY({frozen_array_conversion});
auto frozen_array_union_type = TRY({create_sequence_from_iterable(types.frozen_array_type, identifier, value_name, "frozen_array_method", includes, context)});
return {variant_type} {{ frozen_array_union_type }};
}}
""")

5
Tests/LibWeb/Text/expected/wpt-import/webidl/ecmascript-binding/sequence-conversion.txt
View file

@ -2,12 +2,11 @@ Harness status: OK
Found 8 tests
7 Pass
1 Fail
8 Pass
Pass An array
Pass A generator
Pass An array with an overridden Symbol.iterator
Fail An object with an overriden Symbol.iterator
Pass An object with an overriden Symbol.iterator
Pass An array with an overridden Symbol.iterator on the prototype
Pass An array with an overridden %ArrayIterator%.prototype.next
Pass A holey array with fallback to an accessor on the prototype