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fix contextj joiner short-circuiting bidi check in is_label_valid #90

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fix contextj joiner short-circuiting bidi check in is_label_valid #90

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14 changes: 8 additions & 6 deletions src/validity.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,7 @@ bool is_label_valid(const std::u32string_view label) {
if (c == 0x200c) {
if (i > 0) {
if (std::ranges::binary_search(virama, label[i - 1])) {
return true;
continue;
}
}
if ((i == 0) || (i + 1 >= label.size())) {
Expand All @@ -206,14 +206,16 @@ bool is_label_valid(const std::u32string_view label) {
};
std::u32string_view before = label.substr(0, i);
std::u32string_view after = label.substr(i + 1);
return (std::find_if(before.begin(), before.end(), is_l_or_d) !=
before.end()) &&
(std::find_if(after.begin(), after.end(), is_r_or_d) !=
after.end());
if ((std::find_if(before.begin(), before.end(), is_l_or_d) ==
before.end()) ||
(std::find_if(after.begin(), after.end(), is_r_or_d) ==
after.end())) {
return false;
}
} else if (c == 0x200d) {
if (i > 0) {
if (std::ranges::binary_search(virama, label[i - 1])) {
return true;
continue;
}
}
return false;
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15 changes: 15 additions & 0 deletions tests/to_ascii_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -191,6 +191,21 @@ TEST(to_ascii_tests, bidi_regression) {
<< "multi-label should fail";
}

TEST(to_ascii_tests, contextj_joiner_does_not_bypass_bidi) {
// A ZWNJ preceded by a virama satisfies the ContextJ rule, but that must not
// short-circuit the Bidi validity check for the rest of the label. Here the
// label starts with L (U+0915) so it is an LTR label, and the trailing AL
// (U+0627) violates Rule 5. It must be rejected.
EXPECT_TRUE(ada::idna::to_ascii("\u0915\u094D\u200C\u0627").empty())
<< "valid ZWNJ must not bypass Bidi rule 5";
// Same with ZWJ (U+200D).
EXPECT_TRUE(ada::idna::to_ascii("\u0915\u094D\u200D\u0627").empty())
<< "valid ZWJ must not bypass Bidi rule 5";
// A contextually valid joiner in an otherwise valid label still converts.
EXPECT_EQ(ada::idna::to_ascii("\u0915\u094D\u200C\u0916"), "xn--11bc8nw90g")
<< "valid ZWNJ label must still convert";
}

// Helper: domain-to-ASCII as URL Standard callers use it (to_ascii + forbidden
// domain code point filter). Empty string means failure.
static std::string domain_to_ascii(std::string_view input) {
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