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LibJS: Add spec comments to StringConstructor
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@linusg
linusg committed Apr 13, 2023
1 parent 1b3c3f9 commit 066133d
Showing 1 changed file with 110 additions and 43 deletions.
153 changes: 110 additions & 43 deletions Userland/Libraries/LibJS/Runtime/StringConstructor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,91 +44,158 @@ ThrowCompletionOr<void> StringConstructor::initialize(Realm& realm)
ThrowCompletionOr<Value> StringConstructor::call()
{
auto& vm = this->vm();
auto value = vm.argument(0);

// 1. If value is not present, let s be the empty String.
if (!vm.argument_count())
return PrimitiveString::create(vm, String {});
if (vm.argument(0).is_symbol())
return PrimitiveString::create(vm, TRY_OR_THROW_OOM(vm, vm.argument(0).as_symbol().descriptive_string()));
return TRY(vm.argument(0).to_primitive_string(vm));

// 2. Else,
// a. If NewTarget is undefined and value is a Symbol, return SymbolDescriptiveString(value).
if (value.is_symbol())
return PrimitiveString::create(vm, TRY_OR_THROW_OOM(vm, value.as_symbol().descriptive_string()));

// b. Let s be ? ToString(value).
// 3. If NewTarget is undefined, return s.
return TRY(value.to_primitive_string(vm));
}

// 22.1.1.1 String ( value ), https://tc39.es/ecma262/#sec-string-constructor-string-value
ThrowCompletionOr<NonnullGCPtr<Object>> StringConstructor::construct(FunctionObject& new_target)
{
auto& vm = this->vm();
auto& realm = *vm.current_realm();
auto value = vm.argument(0);

PrimitiveString* primitive_string;
if (!vm.argument_count())

// 1. If value is not present, let s be the empty String.
if (!vm.argument_count()) {
primitive_string = PrimitiveString::create(vm, String {});
else
primitive_string = TRY(vm.argument(0).to_primitive_string(vm));
}
// 2. Else,
else {
// b. Let s be ? ToString(value).
primitive_string = TRY(value.to_primitive_string(vm));
}

// 4. Return StringCreate(s, ? GetPrototypeFromConstructor(NewTarget, "%String.prototype%")).
auto* prototype = TRY(get_prototype_from_constructor(vm, new_target, &Intrinsics::string_prototype));
return MUST_OR_THROW_OOM(StringObject::create(realm, *primitive_string, *prototype));
}

// 22.1.2.4 String.raw ( template, ...substitutions ), https://tc39.es/ecma262/#sec-string.raw
JS_DEFINE_NATIVE_FUNCTION(StringConstructor::raw)
{
auto* cooked = TRY(vm.argument(0).to_object(vm));
auto raw_value = TRY(cooked->get(vm.names.raw));
auto* raw = TRY(raw_value.to_object(vm));
auto literal_segments = TRY(length_of_array_like(vm, *raw));

if (literal_segments == 0)
return PrimitiveString::create(vm, String {});

auto const number_of_substituions = vm.argument_count() - 1;

StringBuilder builder;
for (size_t i = 0; i < literal_segments; ++i) {
auto next_key = DeprecatedString::number(i);
auto next_segment_value = TRY(raw->get(next_key));
auto next_segment = TRY(next_segment_value.to_deprecated_string(vm));

builder.append(next_segment);

if (i + 1 == literal_segments)
break;

if (i < number_of_substituions) {
auto next = vm.argument(i + 1);
auto next_sub = TRY(next.to_deprecated_string(vm));
builder.append(next_sub);
}
}
return PrimitiveString::create(vm, builder.to_deprecated_string());
}

// 22.1.2.1 String.fromCharCode ( ...codeUnits ), https://tc39.es/ecma262/#sec-string.fromcharcode
JS_DEFINE_NATIVE_FUNCTION(StringConstructor::from_char_code)
{
// 1. Let result be the empty String.
Utf16Data string;
string.ensure_capacity(vm.argument_count());

for (size_t i = 0; i < vm.argument_count(); ++i)
string.append(TRY(vm.argument(i).to_u16(vm)));
// 2. For each element next of codeUnits, do
for (size_t i = 0; i < vm.argument_count(); ++i) {
// a. Let nextCU be the code unit whose numeric value is ℝ(? ToUint16(next)).
auto next_code_unit = TRY(vm.argument(i).to_u16(vm));

// b. Set result to the string-concatenation of result and nextCU.
string.append(next_code_unit);
}

// 3. Return result.
return PrimitiveString::create(vm, TRY(Utf16String::create(vm, move(string))));
}

// 22.1.2.2 String.fromCodePoint ( ...codePoints ), https://tc39.es/ecma262/#sec-string.fromcodepoint
JS_DEFINE_NATIVE_FUNCTION(StringConstructor::from_code_point)
{
// 1. Let result be the empty String.
Utf16Data string;
string.ensure_capacity(vm.argument_count()); // This will be an under-estimate if any code point is > 0xffff.
// This will be an under-estimate if any code point is > 0xffff.
string.ensure_capacity(vm.argument_count());

// 2. For each element next of codePoints, do
for (size_t i = 0; i < vm.argument_count(); ++i) {
// a. Let nextCP be ? ToNumber(next).
auto next_code_point = TRY(vm.argument(i).to_number(vm));

// b. If IsIntegralNumber(nextCP) is false, throw a RangeError exception.
if (!next_code_point.is_integral_number())
return vm.throw_completion<RangeError>(ErrorType::InvalidCodePoint, TRY_OR_THROW_OOM(vm, next_code_point.to_string_without_side_effects()));
auto code_point = TRY(next_code_point.to_i32(vm));

auto code_point = MUST(next_code_point.to_i32(vm));

// c. If ℝ(nextCP) < 0 or ℝ(nextCP) > 0x10FFFF, throw a RangeError exception.
if (code_point < 0 || code_point > 0x10FFFF)
return vm.throw_completion<RangeError>(ErrorType::InvalidCodePoint, TRY_OR_THROW_OOM(vm, next_code_point.to_string_without_side_effects()));

// d. Set result to the string-concatenation of result and UTF16EncodeCodePoint(ℝ(nextCP)).
TRY_OR_THROW_OOM(vm, code_point_to_utf16(string, static_cast<u32>(code_point)));
}

// 3. Assert: If codePoints is empty, then result is the empty String.
if (!vm.argument_count())
VERIFY(string.is_empty());

// 4. Return result.
return PrimitiveString::create(vm, TRY(Utf16String::create(vm, move(string))));
}

// 22.1.2.4 String.raw ( template, ...substitutions ), https://tc39.es/ecma262/#sec-string.raw
JS_DEFINE_NATIVE_FUNCTION(StringConstructor::raw)
{
auto template_ = vm.argument(0);

// 1. Let substitutionCount be the number of elements in substitutions.
auto substitution_count = vm.argument_count() > 0 ? vm.argument_count() - 1 : 0;

// 2. Let cooked be ? ToObject(template).
auto* cooked = TRY(template_.to_object(vm));

// 3. Let literals be ? ToObject(? Get(cooked, "raw")).
auto* literals = TRY(TRY(cooked->get(vm.names.raw)).to_object(vm));

// 4. Let literalCount be ? LengthOfArrayLike(literals).
auto literal_count = TRY(length_of_array_like(vm, *literals));

// 5. If literalCount ≤ 0, return the empty String.
if (literal_count == 0)
return PrimitiveString::create(vm, String {});

// 6. Let R be the empty String.
StringBuilder builder;

// 7. Let nextIndex be 0.
// 8. Repeat,
for (size_t i = 0; i < literal_count; ++i) {
auto next_key = DeprecatedString::number(i);

// a. Let nextLiteralVal be ? Get(literals, ! ToString(𝔽(nextIndex))).
auto next_literal_value = TRY(literals->get(next_key));

// b. Let nextLiteral be ? ToString(nextLiteralVal).
auto next_literal = TRY(next_literal_value.to_deprecated_string(vm));

// c. Set R to the string-concatenation of R and nextLiteral.
builder.append(next_literal);

// d. If nextIndex + 1 = literalCount, return R.
if (i + 1 == literal_count)
break;

// e. If nextIndex < substitutionCount, then
if (i < substitution_count) {
// i. Let nextSubVal be substitutions[nextIndex].
auto next_substitution_value = vm.argument(i + 1);

// ii. Let nextSub be ? ToString(nextSubVal).
auto next_substitution = TRY(next_substitution_value.to_deprecated_string(vm));

// iii. Set R to the string-concatenation of R and nextSub.
builder.append(next_substitution);
}

// f. Set nextIndex to nextIndex + 1.
}
return PrimitiveString::create(vm, builder.to_deprecated_string());
}

}

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