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test(email): expand is_idn_email coverage for the address-literal branch #2698

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test(email): expand is_idn_email coverage for the address-literal branch #2698

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253 changes: 253 additions & 0 deletions test/email/idn_email_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -528,3 +528,256 @@ TEST(valid_ulabel_local_and_alabel_domain) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("\xce\xb1@xn--nxasmq6b.com"));
EXPECT_FALSE(sourcemeta::core::is_email("\xce\xb1@xn--nxasmq6b.com"));
}

// --- RFC 5321 §4.1.3 address-literal: Snum ---------------------------------

// RFC 5321 §4.1.3: Snum = 1*3DIGIT "representing a decimal integer value in
// the range 0 through 255". The rule constrains the VALUE, not the digit
// count, so leading zeros are inside the grammar. This is the documented
// difference from the RFC 3986 dec-octet that backs is_ipv4, which forbids
// them - so an implementation that reuses its ipv4 checker here is wrong.
TEST(valid_address_literal_snum_leading_zero) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[01.0.0.1]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[01.0.0.1]"));
}

TEST(valid_address_literal_snum_leading_zero_last_octet) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[0.0.0.01]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[0.0.0.01]"));
}

TEST(valid_address_literal_snum_leading_zeros_every_octet) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[001.002.003.004]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[001.002.003.004]"));
}

TEST(valid_address_literal_snum_padded_zero_octets) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[000.000.000.000]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[000.000.000.000]"));
}

TEST(valid_address_literal_snum_maximum) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[255.255.255.255]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[255.255.255.255]"));
}

// One over the range the comment in the ABNF gives
TEST(invalid_address_literal_snum_over_maximum) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[256.0.0.1]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[256.0.0.1]"));
}

// 1*3DIGIT caps the digit count at three even when the value fits
TEST(invalid_address_literal_snum_four_digits) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[0255.0.0.1]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[0255.0.0.1]"));
}

// RFC 5321 §4.1.3: IPv4-address-literal = Snum 3("." Snum), so exactly four
TEST(invalid_address_literal_three_octets) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[1.2.3]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[1.2.3]"));
}

TEST(invalid_address_literal_five_octets) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[1.2.3.4.5]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[1.2.3.4.5]"));
}

TEST(invalid_address_literal_trailing_dot) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[1.2.3.]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[1.2.3.]"));
}

TEST(invalid_address_literal_leading_dot) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[.1.2.3]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[.1.2.3]"));
}

TEST(invalid_address_literal_empty_octet) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[1..2.3]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[1..2.3]"));
}

// --- RFC 5321 §4.1.3 General-address-literal -------------------------------

// General-address-literal = Standardized-tag ":" 1*dcontent
TEST(valid_general_address_literal) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[unknown-tag:abc]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[unknown-tag:abc]"));
}

TEST(valid_general_address_literal_shortest) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[a:b]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[a:b]"));
}

// RFC 5321 §4.1.2: Ldh-str = *( ALPHA / DIGIT / "-" ) Let-dig constrains only
// the final character, so unlike sub-domain (Let-dig [Ldh-str]) a
// Standardized-tag may begin with a hyphen
TEST(valid_general_address_literal_leading_hyphen_tag) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[-tag:abc]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[-tag:abc]"));
}

TEST(invalid_general_address_literal_trailing_hyphen_tag) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[tag-:abc]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[tag-:abc]"));
}

// 1*dcontent requires at least one octet
TEST(invalid_general_address_literal_empty_content) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[tag:]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[tag:]"));
}

TEST(invalid_general_address_literal_empty_tag) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[:abc]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[:abc]"));
}

// RFC 5321 §4.1.3: dcontent = %d33-90 / %d94-126, which excludes SP, "[",
// "\" and "]"
TEST(invalid_general_address_literal_space_in_content) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[tag:ab c]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[tag:ab c]"));
}

TEST(invalid_general_address_literal_open_bracket_in_content) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[tag:ab[c]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[tag:ab[c]"));
}

// --- RFC 5321 §4.1.3 IPv6-address-literal ----------------------------------

// IPv6-comp permits an empty prefix and suffix around "::"
TEST(valid_address_literal_ipv6_fully_compressed) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[IPv6:::1]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[IPv6:::1]"));
}

// RFC 5234 §2.3: ABNF literal strings are case-insensitive, so the tag matches
// in any case. The lowercase form is already covered; this pins the uppercase.
TEST(valid_address_literal_ipv6_uppercase_tag) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("user@[IPV6:2001:db8::1]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[IPV6:2001:db8::1]"));
}

// IPv6v4-comp = [IPv6-hex *3(":" IPv6-hex)] "::" [...] IPv4-address-literal
TEST(valid_address_literal_ipv6v4_comp) {
EXPECT_TRUE(
sourcemeta::core::is_idn_email("user@[IPv6:2001:db8::192.0.2.1]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[IPv6:2001:db8::192.0.2.1]"));
}

// IPv6v4-full = IPv6-hex 5(":" IPv6-hex) ":" IPv4-address-literal
TEST(valid_address_literal_ipv6v4_full) {
EXPECT_TRUE(
sourcemeta::core::is_idn_email("user@[IPv6:1:2:3:4:5:6:1.2.3.4]"));
EXPECT_TRUE(sourcemeta::core::is_email("user@[IPv6:1:2:3:4:5:6:1.2.3.4]"));
}

TEST(invalid_address_literal_ipv6_empty) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[IPv6:]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[IPv6:]"));
}

// --- address-literal shape -------------------------------------------------

TEST(invalid_address_literal_empty) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[]"));
}

TEST(invalid_address_literal_unterminated) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[192.0.2.1"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[192.0.2.1"));
}

TEST(invalid_address_literal_doubled_brackets) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[[192.0.2.1]]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[[192.0.2.1]]"));
}

TEST(invalid_address_literal_followed_by_label) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[192.0.2.1].com"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[192.0.2.1].com"));
}

TEST(invalid_address_literal_trailing_space) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user@[192.0.2.1 ]"));
EXPECT_FALSE(sourcemeta::core::is_email("user@[192.0.2.1 ]"));
}

// --- the "@" delimiter -----------------------------------------------------

// RFC 5321 §4.1.2: Mailbox splits on U+0040. A fullwidth (U+FF20, EF BC A0) or
// small (U+FE6B, EF B9 AB) commercial at is an ordinary character, so a string
// carrying one instead of "@" has no delimiter at all. Both codepoints map to
// U+0040 in the UTS #46 table, but that mapping applies to the domain the
// split produces, so it cannot manufacture the delimiter.
TEST(invalid_fullwidth_commercial_at) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user\xef\xbc\xa0"
"example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("user\xef\xbc\xa0"
"example.com"));
}

TEST(invalid_small_commercial_at) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("user\xef\xb9\xab"
"example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("user\xef\xb9\xab"
"example.com"));
}

// --- local-part codepoints the ABNF admits ---------------------------------

// RFC 6531 §3.3 extends atext with UTF8-non-ascii and RFC 6532 §3.1 defines
// that as UTF8-2 / UTF8-3 / UTF8-4, with no codepoint-class filter. So a C1
// control, a noncharacter and a supplementary private-use codepoint are all
// inside the local-part grammar even though they are unusual.
// U+0085 NEXT LINE (C2 85)
TEST(valid_local_c1_control) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("\xc2\x85@example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("\xc2\x85@example.com"));
}

// U+FFFE noncharacter (EF BF BE)
TEST(valid_local_noncharacter) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("\xef\xbf\xbe@example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("\xef\xbf\xbe@example.com"));
}

// U+FDD0, the start of the noncharacter block (EF B7 90)
TEST(valid_local_noncharacter_block) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("\xef\xb7\x90@example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("\xef\xb7\x90@example.com"));
}

// U+F0000, a supplementary private-use codepoint (F3 B0 80 80)
TEST(valid_local_supplementary_private_use) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("\xf3\xb0\x80\x80@example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("\xf3\xb0\x80\x80@example.com"));
}

// --- Quoted-string structure -----------------------------------------------

@jviotti jviotti Jul 31, 2026

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Can you remove section comments?


// RFC 5321 §4.1.2: Quoted-string = DQUOTE *QcontentSMTP DQUOTE, so the closing
// DQUOTE is mandatory
TEST(invalid_quoted_local_unterminated) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("\"unterminated@example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("\"unterminated@example.com"));
}

// Local-part = Dot-string / Quoted-string, so a quoted string cannot be
// followed by more local-part text
TEST(invalid_quoted_local_trailing_text) {
EXPECT_FALSE(sourcemeta::core::is_idn_email("\"a\"b@example.com"));
EXPECT_FALSE(sourcemeta::core::is_email("\"a\"b@example.com"));
}

// quoted-pairSMTP = %d92 %d32-126, so a backslash may escape the DQUOTE
TEST(valid_quoted_local_escaped_dquote) {
EXPECT_TRUE(sourcemeta::core::is_idn_email("\"\\\"\"@example.com"));
EXPECT_TRUE(sourcemeta::core::is_email("\"\\\"\"@example.com"));
}
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