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LibJS: Implement the GetSubstitution AO according to the spec

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There was recently a normative change to this AO in ECMA-262. See:
5eaee2f

It turns out we already implemented this to align with web-reality
before it was codified in the spec. This was a bit difficult to reason
without spec text and with a somewhat ad-hoc implementation. So this
patch aligns our implementation with the spec. There should not be any
behavior change.
This commit is contained in:
Timothy Flynn 2024-01-03 13:21:54 -05:00 • committed by Andreas Kling
parent 8de1db7b78
commit 6d1c10ed10
1 changed files with 164 additions and 67 deletions
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231
Userland/Libraries/LibJS/Runtime/AbstractOperations.cpp
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@ -34,6 +34,7 @@
#include <LibJS/Runtime/PropertyKey.h>
#include <LibJS/Runtime/ProxyObject.h>
#include <LibJS/Runtime/Reference.h>
#include <LibJS/Runtime/StringPrototype.h>
#include <LibJS/Runtime/SuppressedError.h>
#include <LibJS/Runtime/ValueInlines.h>
@ -1215,97 +1216,193 @@ CanonicalIndex canonical_numeric_index_string(PropertyKey const& property_key, C
// 22.1.3.19.1 GetSubstitution ( matched, str, position, captures, namedCaptures, replacementTemplate ), https://tc39.es/ecma262/#sec-getsubstitution
ThrowCompletionOr<String> get_substitution(VM& vm, Utf16View const& matched, Utf16View const& str, size_t position, Span<Value> captures, Value named_captures, Value replacement_template)
{
auto replace_string = TRY(replacement_template.to_utf16_string(vm));
auto replace_view = replace_string.view();
// 1. Let stringLength be the length of str.
auto string_length = str.length_in_code_units();
// 2. Assert: position ≤ stringLength.
VERIFY(position <= string_length);
// 3. Let result be the empty String.
Utf16Data result;
for (size_t i = 0; i < replace_view.length_in_code_units(); ++i) {
u16 curr = replace_view.code_unit_at(i);
// 4. Let templateRemainder be replacementTemplate.
auto replace_template_string = TRY(replacement_template.to_utf16_string(vm));
auto template_remainder = replace_template_string.view();
if ((curr != '$') || (i + 1 >= replace_view.length_in_code_units())) {
TRY_OR_THROW_OOM(vm, result.try_append(curr));
continue;
// 5. Repeat, while templateRemainder is not the empty String,
while (!template_remainder.is_empty()) {
// a. NOTE: The following steps isolate ref (a prefix of templateRemainder), determine refReplacement (its replacement), and then append that replacement to result.
Utf16View ref;
Utf16View ref_replacement;
Optional<Utf16String> capture_string;
// b. If templateRemainder starts with "$$", then
if (template_remainder.starts_with(u"$$")) {
// i. Let ref be "$$".
ref = u"$$";
// ii. Let refReplacement be "$".
ref_replacement = u"$";
}
// c. Else if templateRemainder starts with "$`", then
else if (template_remainder.starts_with(u"$`")) {
// i. Let ref be "$`".
ref = u"$`";
u16 next = replace_view.code_unit_at(i + 1);
// ii. Let refReplacement be the substring of str from 0 to position.
ref_replacement = str.substring_view(0, position);
}
// d. Else if templateRemainder starts with "$&", then
else if (template_remainder.starts_with(u"$&")) {
// i. Let ref be "$&".
ref = u"$&";
if (next == '$') {
TRY_OR_THROW_OOM(vm, result.try_append('$'));
++i;
} else if (next == '&') {
TRY_OR_THROW_OOM(vm, result.try_append(matched.data(), matched.length_in_code_units()));
++i;
} else if (next == '`') {
auto substring = str.substring_view(0, position);
TRY_OR_THROW_OOM(vm, result.try_append(substring.data(), substring.length_in_code_units()));
++i;
} else if (next == '\'') {
auto tail_pos = position + matched.length_in_code_units();
if (tail_pos < str.length_in_code_units()) {
auto substring = str.substring_view(tail_pos);
TRY_OR_THROW_OOM(vm, result.try_append(substring.data(), substring.length_in_code_units()));
}
++i;
} else if (is_ascii_digit(next)) {
bool is_two_digits = (i + 2 < replace_view.length_in_code_units()) && is_ascii_digit(replace_view.code_unit_at(i + 2));
// ii. Let refReplacement be matched.
ref_replacement = matched;
}
// e. Else if templateRemainder starts with "$'" (0x0024 (DOLLAR SIGN) followed by 0x0027 (APOSTROPHE)), then
else if (template_remainder.starts_with(u"$'")) {
// i. Let ref be "$'".
ref = u"$'";
auto capture_position_string = TRY_OR_THROW_OOM(vm, replace_view.substring_view(i + 1, is_two_digits ? 2 : 1).to_utf8());
auto capture_position = capture_position_string.to_number<u32>();
// ii. Let matchLength be the length of matched.
auto match_length = matched.length_in_code_units();
// NOTE: All major engines treat $10 as $1 followed by a literal '0' character
// if there are fewer than 10 capture groups. The spec disagrees.
// Spec bug: https://github.com/tc39/ecma262/issues/1426
if (is_two_digits && capture_position.has_value() && (*capture_position > 0) && (*capture_position > captures.size())) {
is_two_digits = false;
capture_position_string = MUST(capture_position_string.substring_from_byte_offset(0, 1));
capture_position = capture_position_string.to_number<u32>();
// iii. Let tailPos be position + matchLength.
auto tail_pos = position + match_length;
// iv. Let refReplacement be the substring of str from min(tailPos, stringLength).
ref_replacement = str.substring_view(min(tail_pos, string_length));
// v. NOTE: tailPos can exceed stringLength only if this abstract operation was invoked by a call to the intrinsic @@replace method of %RegExp.prototype% on an object whose "exec" property is not the intrinsic %RegExp.prototype.exec%.
}
// f. Else if templateRemainder starts with "$" followed by 1 or more decimal digits, then
else if (template_remainder.starts_with(u"$") && template_remainder.length_in_code_units() > 1 && is_ascii_digit(template_remainder.code_unit_at(1))) {
// i. If templateRemainder starts with "$" followed by 2 or more decimal digits, let digitCount be 2. Otherwise, let digitCount be 1.
size_t digit_count = 1;
if (template_remainder.length_in_code_units() > 2 && is_ascii_digit(template_remainder.code_point_at(2)))
digit_count = 2;
// ii. Let digits be the substring of templateRemainder from 1 to 1 + digitCount.
auto digits = template_remainder.substring_view(1, digit_count);
// iii. Let index be ℝ(StringToNumber(digits)).
auto utf8_digits = MUST(digits.to_utf8());
auto index = static_cast<size_t>(string_to_number(utf8_digits));
// iv. Assert: 0 ≤ index ≤ 99.
VERIFY(index <= 99);
// v. Let captureLen be the number of elements in captures.
auto capture_length = captures.size();
// vi. If index > captureLen and digitCount = 2, then
if (index > capture_length && digit_count == 2) {
// 1. NOTE: When a two-digit replacement pattern specifies an index exceeding the count of capturing groups, it is treated as a one-digit replacement pattern followed by a literal digit.
// 2. Set digitCount to 1.
digit_count = 1;
// 3. Set digits to the substring of digits from 0 to 1.
digits = digits.substring_view(0, 1);
// 4. Set index to ℝ(StringToNumber(digits)).
utf8_digits = MUST(digits.to_utf8());
index = static_cast<size_t>(string_to_number(utf8_digits));
}
if (capture_position.has_value() && (*capture_position > 0) && (*capture_position <= captures.size())) {
auto& value = captures[*capture_position - 1];
// vii. Let ref be the substring of templateRemainder from 0 to 1 + digitCount.
ref = template_remainder.substring_view(0, 1 + digit_count);
if (!value.is_undefined()) {
auto value_string = TRY(value.to_utf16_string(vm));
TRY_OR_THROW_OOM(vm, result.try_append(value_string.view().data(), value_string.length_in_code_units()));
// viii. If 1 ≤ index ≤ captureLen, then
if (1 <= index && index <= capture_length) {
// 1. Let capture be captures[index - 1].
auto capture = captures[index - 1];
// 2. If capture is undefined, then
if (capture.is_undefined()) {
// a. Let refReplacement be the empty String.
ref_replacement = {};
}
i += is_two_digits ? 2 : 1;
} else {
TRY_OR_THROW_OOM(vm, result.try_append(curr));
}
} else if (next == '<') {
auto start_position = i + 2;
Optional<size_t> end_position;
for (size_t j = start_position; j < replace_view.length_in_code_units(); ++j) {
if (replace_view.code_unit_at(j) == '>') {
end_position = j;
break;
// 3. Else,
else {
// a. Let refReplacement be capture.
capture_string = TRY(capture.to_utf16_string(vm));
ref_replacement = capture_string->view();
}
}
// ix. Else,
else {
// 1. Let refReplacement be ref.
ref_replacement = ref;
}
}
// g. Else if templateRemainder starts with "$<", then
else if (template_remainder.starts_with(u"$<")) {
// i. Let gtPos be StringIndexOf(templateRemainder, ">", 0).
// NOTE: We can actually start at index 2 because we know the string starts with "$<".
auto greater_than_position = string_index_of(template_remainder, u">", 2);
if (named_captures.is_undefined() || !end_position.has_value()) {
TRY_OR_THROW_OOM(vm, result.try_append(curr));
} else {
auto group_name_view = replace_view.substring_view(start_position, *end_position - start_position);
auto group_name = TRY_OR_THROW_OOM(vm, group_name_view.to_byte_string(Utf16View::AllowInvalidCodeUnits::Yes));
// ii. If gtPos = -1 or namedCaptures is undefined, then
if (!greater_than_position.has_value() || named_captures.is_undefined()) {
// 1. Let ref be "$<".
ref = u"$<";
// 2. Let refReplacement be ref.
ref_replacement = ref;
}
// iii. Else,
else {
// 1. Let ref be the substring of templateRemainder from 0 to gtPos + 1.
ref = template_remainder.substring_view(0, *greater_than_position + 1);
// 2. Let groupName be the substring of templateRemainder from 2 to gtPos.
auto group_name_view = template_remainder.substring_view(2, *greater_than_position - 2);
auto group_name = MUST(group_name_view.to_byte_string(Utf16View::AllowInvalidCodeUnits::Yes));
// 3. Assert: namedCaptures is an Object.
VERIFY(named_captures.is_object());
// 4. Let capture be ? Get(namedCaptures, groupName).
auto capture = TRY(named_captures.as_object().get(group_name));
if (!capture.is_undefined()) {
auto capture_string = TRY(capture.to_utf16_string(vm));
TRY_OR_THROW_OOM(vm, result.try_append(capture_string.view().data(), capture_string.length_in_code_units()));
// 5. If capture is undefined, then
if (capture.is_undefined()) {
// a. Let refReplacement be the empty String.
ref_replacement = {};
}
// 6. Else,
else {
// a. Let refReplacement be ? ToString(capture).
capture_string = TRY(capture.to_utf16_string(vm));
ref_replacement = capture_string->view();
}
i = *end_position;
}
} else {
TRY_OR_THROW_OOM(vm, result.try_append(curr));
}
// h. Else,
else {
// i. Let ref be the substring of templateRemainder from 0 to 1.
ref = template_remainder.substring_view(0, 1);
// ii. Let refReplacement be ref.
ref_replacement = ref;
}
// i. Let refLength be the length of ref.
auto ref_length = ref.length_in_code_units();
// k. Set result to the string-concatenation of result and refReplacement.
result.append(ref_replacement.data(), ref_replacement.length_in_code_points());
// j. Set templateRemainder to the substring of templateRemainder from refLength.
// NOTE: We do this step last because refReplacement may point to templateRemainder.
template_remainder = template_remainder.substring_view(ref_length);
}
return TRY_OR_THROW_OOM(vm, Utf16View { result }.to_utf8());
// 6. Return result.
return MUST(Utf16View { result }.to_utf8());
}
// 2.1.2 AddDisposableResource ( disposable, V, hint [ , method ] ), https://tc39.es/proposal-explicit-resource-management/#sec-adddisposableresource-disposable-v-hint-disposemethod