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LibJS: Unescape incorrectly escaped code units in regex patterns

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We were translating the pattern [\⪾-\⫀] to [\\u2abe-\\u2ac0], which
is a very different pattern; as a code unit converted to the \uhhh
format has no meaning when escaped, this commit makes us simply skip
escaping it when translating the pattern.
This commit is contained in:
Ali Mohammad Pur 2023-09-16 16:03:54 +03:30 • committed by Andreas Kling
parent 35ff38aaea
commit 17087ac4a2
2 changed files with 22 additions and 3 deletions
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19
Userland/Libraries/LibJS/Runtime/RegExpObject.cpp
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@ -100,6 +100,7 @@ ErrorOr<DeprecatedString, ParseRegexPatternError> parse_regex_pattern(StringView
// If the Unicode flag is set, append each code point to the pattern. Otherwise, append each
// code unit. But unlike the spec, multi-byte code units must be escaped for LibRegex to parse.
auto previous_code_unit_was_backslash = false;
for (size_t i = 0; i < utf16_pattern_view.length_in_code_units();) {
if (unicode || unicode_sets) {
auto code_point = code_point_at(utf16_pattern_view, i);
@ -111,10 +112,22 @@ ErrorOr<DeprecatedString, ParseRegexPatternError> parse_regex_pattern(StringView
u16 code_unit = utf16_pattern_view.code_unit_at(i);
++i;
if (code_unit > 0x7f)
builder.appendff("\\u{:04x}", code_unit);
else
if (code_unit > 0x7f) {
// Incorrectly escaping this code unit will result in a wildly different regex than intended
// as we're converting <c> to <\uhhhh>, which would turn into <\\uhhhh> if (incorrectly) escaped again,
// leading to a matcher for the literal string "\uhhhh" instead of the intended code unit <c>.
// As such, we're going to remove the (invalid) backslash and pretend it never existed.
if (!previous_code_unit_was_backslash)
builder.append('\\');
builder.appendff("u{:04x}", code_unit);
} else {
builder.append_code_point(code_unit);
}
if (code_unit == '\\')
previous_code_unit_was_backslash = !previous_code_unit_was_backslash;
else
previous_code_unit_was_backslash = false;
}
return builder.to_deprecated_string();