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Add keep parameter to dump to copy invalid UTF-8 bytes as-is #4555

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Add keep parameter to dump to copy invalid UTF-8 bytes as-is #4555

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4d67e12
:construction: WIP for #4552
nlohmann Dec 18, 2024
851584e
Set parents after insert call (#4537)
nlohmann Dec 18, 2024
3665dab
Suppress modernize-use-integer-sign-comparison (#4558)
nlohmann Dec 18, 2024
1a76a2c
:art: fix format
nlohmann Dec 18, 2024
3db5cc4
Bump actions/upload-artifact from 4.4.3 to 4.5.0 (#4557)
dependabot[bot] Dec 18, 2024
9f73bc1
json start/end position implementation (#4517)
sushshring Dec 18, 2024
a27a5b5
Add ONLY_SERIALIZE for NLOHMANN_DEFINE_DERIVED_TYPE_* macros (#4562)
EinarsNG Dec 20, 2024
a2d828c
:construction: first implementation for keep
nlohmann Dec 20, 2024
7d2a83b
:rotating_light: fix warning
nlohmann Dec 20, 2024
a6a06b7
Merge branch 'develop' into issue4552-ignore
nlohmann Dec 22, 2024
3cd5025
:construction: add support for ensure_ascii
nlohmann Dec 22, 2024
15ff370
:rotating_light: fix warnings
nlohmann Dec 22, 2024
e9876d9
:art: format code
nlohmann Dec 22, 2024
b167096
:memo: clean up
nlohmann Dec 22, 2024
493d1e4
:rotating_light: fix warnings
nlohmann Dec 22, 2024
4ab98c3
Update docs/mkdocs/docs/api/basic_json/dump.md
nlohmann Dec 23, 2024
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10 changes: 6 additions & 4 deletions docs/mkdocs/docs/api/basic_json/dump.md
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Expand Up @@ -25,10 +25,11 @@ and `ensure_ascii` parameters.
result consists of ASCII characters only.

`error_handler` (in)
: how to react on decoding errors; there are three possible values (see [`error_handler_t`](error_handler_t.md):
`strict` (throws and exception in case a decoding error occurs; default), `replace` (replace invalid UTF-8 sequences
with U+FFFD), and `ignore` (ignore invalid UTF-8 sequences during serialization; all bytes are copied to the output
unchanged)).
: how to react on decoding errors; there are three possible values (see [`error_handler_t`](error_handler_t.md)):
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: - `strict`: throws a [`type_error`](../../home/exceptions.md#type-errors) exception in case a decoding error occurs (this is the default),
- `replace`: replace invalid UTF-8 sequences with U+FFFD (� REPLACEMENT CHARACTER),
- `ignore`: ignore invalid UTF-8 sequences during serialization (i.e., these bytes are skipped and not copied to the output), and
- `keep`: keep invalid UTF-8 sequences during serialization (i.e., all bytes are copied to the output unchanged)

## Return value

Expand Down Expand Up @@ -77,3 +78,4 @@ Binary values are serialized as object containing two keys:
- Indentation character `indent_char`, option `ensure_ascii` and exceptions added in version 3.0.0.
- Error handlers added in version 3.4.0.
- Serialization of binary values added in version 3.8.0.
- Added support for error handler value `keep` in version ???.
8 changes: 6 additions & 2 deletions docs/mkdocs/docs/api/basic_json/error_handler_t.md
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Expand Up @@ -12,13 +12,16 @@ This enumeration is used in the [`dump`](dump.md) function to choose how to trea
`basic_json` value. Three values are differentiated:

strict
: throw a `type_error` exception in case of invalid UTF-8
: throw a [`type_error`](../../home/exceptions.md#type-errors) exception in case of invalid UTF-8

replace
: replace invalid UTF-8 sequences with U+FFFD (� REPLACEMENT CHARACTER)

ignore
: ignore invalid UTF-8 sequences; all bytes are copied to the output unchanged
: ignore invalid UTF-8 sequences; these bytes are skipped and not copied to the output

keep
: keep invalid UTF-8 sequences; all bytes are copied to the output unchanged

## Examples

Expand All @@ -40,3 +43,4 @@ ignore
## Version history

- Added in version 3.4.0.
- Added value `keep` in version ???.
46 changes: 42 additions & 4 deletions include/nlohmann/detail/output/serializer.hpp
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Expand Up @@ -44,7 +44,8 @@ enum class error_handler_t
{
strict, ///< throw a type_error exception in case of invalid UTF-8
replace, ///< replace invalid UTF-8 sequences with U+FFFD
ignore ///< ignore invalid UTF-8 sequences
ignore, ///< ignore invalid UTF-8 sequences
keep ///< keep invalid UTF-8 sequences
};

template<typename BasicJsonType>
Expand Down Expand Up @@ -398,6 +399,13 @@ class serializer
std::size_t bytes_after_last_accept = 0;
std::size_t undumped_chars = 0;

// copy string as-is if error handler is set to keep, and we don't want to ensure ASCII
if (error_handler == error_handler_t::keep && !ensure_ascii)
{
o->write_characters(s.data(), s.size());
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Just for me to understand, how would this behave exactly? If there is a 0×dc byte for example, it will be escaped as \334 octal string (or \xdc hex, or similar)?

I think the important thing is to not break the json format.

And also what about other UTF-8 accepted chars? Like \b or \t handled below: how will they be dumped in this case?

I have limited access these days (from mobile), and I don't know exactly the purpose of ensure_ascii and its default value. If you could provide some hint it would be helpful.

Thank you

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Oh, you're right! Just copying the input to the output is wrong here, because valid characters like LF that must be escaped to \n would not be escaped and the resulting JSON would be invalid. Thanks for noting. I will fix this.

return;
}

for (std::size_t i = 0; i < s.size(); ++i)
{
const auto byte = static_cast<std::uint8_t>(s[i]);
Expand Down Expand Up @@ -567,7 +575,23 @@ class serializer
break;
}

default: // LCOV_EXCL_LINE
case error_handler_t::keep:
{
// copy undumped chars to string buffer
for (std::size_t j = 0; j < undumped_chars; ++j)
{
string_buffer[bytes++] = s[bytes_after_last_accept + j];
}

// add erroneous byte to string buffer
string_buffer[bytes++] = s[i];

// continue processing the string
state = UTF8_ACCEPT;
break;
}

default: // LCOV_EXCL_LINE
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
}
break;
Expand Down Expand Up @@ -605,6 +629,20 @@ class serializer
JSON_THROW(type_error::create(316, concat("incomplete UTF-8 string; last byte: 0x", hex_bytes(static_cast<std::uint8_t>(s.back() | 0))), nullptr));
}

case error_handler_t::keep:
{
// copy undumped chars to string buffer
for (std::size_t j = 0; j < undumped_chars; ++j)
{
string_buffer[bytes++] = s[bytes_after_last_accept + j];
}
undumped_chars = 0;

// write all accepted bytes
o->write_characters(string_buffer.data(), bytes);
break;
}

case error_handler_t::ignore:
{
// write all accepted bytes
Expand All @@ -628,8 +666,8 @@ class serializer
break;
}

default: // LCOV_EXCL_LINE
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
default: // LCOV_EXCL_LINE
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
}
}
}
Expand Down
46 changes: 42 additions & 4 deletions single_include/nlohmann/json.hpp
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Expand Up @@ -18606,7 +18606,8 @@ enum class error_handler_t
{
strict, ///< throw a type_error exception in case of invalid UTF-8
replace, ///< replace invalid UTF-8 sequences with U+FFFD
ignore ///< ignore invalid UTF-8 sequences
ignore, ///< ignore invalid UTF-8 sequences
keep ///< keep invalid UTF-8 sequences
};

template<typename BasicJsonType>
Expand Down Expand Up @@ -18960,6 +18961,13 @@ class serializer
std::size_t bytes_after_last_accept = 0;
std::size_t undumped_chars = 0;

// copy string as-is if error handler is set to keep, and we don't want to ensure ASCII
if (error_handler == error_handler_t::keep && !ensure_ascii)
{
o->write_characters(s.data(), s.size());
return;
}

for (std::size_t i = 0; i < s.size(); ++i)
{
const auto byte = static_cast<std::uint8_t>(s[i]);
Expand Down Expand Up @@ -19129,7 +19137,23 @@ class serializer
break;
}

default: // LCOV_EXCL_LINE
case error_handler_t::keep:
{
// copy undumped chars to string buffer
for (std::size_t j = 0; j < undumped_chars; ++j)
{
string_buffer[bytes++] = s[bytes_after_last_accept + j];
}

// add erroneous byte to string buffer
string_buffer[bytes++] = s[i];

// continue processing the string
state = UTF8_ACCEPT;
break;
}

default: // LCOV_EXCL_LINE
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
}
break;
Expand Down Expand Up @@ -19167,6 +19191,20 @@ class serializer
JSON_THROW(type_error::create(316, concat("incomplete UTF-8 string; last byte: 0x", hex_bytes(static_cast<std::uint8_t>(s.back() | 0))), nullptr));
}

case error_handler_t::keep:
{
// copy undumped chars to string buffer
for (std::size_t j = 0; j < undumped_chars; ++j)
{
string_buffer[bytes++] = s[bytes_after_last_accept + j];
}
undumped_chars = 0;

// write all accepted bytes
o->write_characters(string_buffer.data(), bytes);
break;
}

case error_handler_t::ignore:
{
// write all accepted bytes
Expand All @@ -19190,8 +19228,8 @@ class serializer
break;
}

default: // LCOV_EXCL_LINE
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
default: // LCOV_EXCL_LINE
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
}
}
}
Expand Down
9 changes: 9 additions & 0 deletions tests/src/unit-regression2.cpp
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Expand Up @@ -995,6 +995,15 @@ TEST_CASE("regression tests 2")
CHECK(p.x == 1);
CHECK(p.y == 2);
}

SECTION("issue #4552 - UTF-8 invalid characters are not always ignored when dumping with error_handler_t::ignore")
{
nlohmann::json node;
node["test"] = "test\334\005";
CHECK(node.dump(-1, ' ', false, nlohmann::json::error_handler_t::ignore) == "{\"test\":\"test\\u0005\"}");
CHECK(node.dump(-1, ' ', false, nlohmann::json::error_handler_t::keep) == "{\"test\":\"test\334\005\"}");
CHECK(node.dump(-1, ' ', true, nlohmann::json::error_handler_t::keep) == "{\"test\":\"test\334\005\"}");
}
}

DOCTEST_CLANG_SUPPRESS_WARNING_POP
11 changes: 11 additions & 0 deletions tests/src/unit-serialization.cpp
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Expand Up @@ -86,8 +86,11 @@ TEST_CASE("serialization")
CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9", json::type_error&);
CHECK_THROWS_WITH_AS(j.dump(1, ' ', false, json::error_handler_t::strict), "[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9", json::type_error&);
CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"äü\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::ignore) == "\"\\u00e4\\u00fc\"");
CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"ä\xEF\xBF\xBDü\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"\\u00e4\\ufffd\\u00fc\"");
CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == "\"ä\xA9ü\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::keep) == "\"\\u00e4\xA9\\u00fc\"");
}

SECTION("ending with incomplete character")
Expand All @@ -97,8 +100,11 @@ TEST_CASE("serialization")
CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] incomplete UTF-8 string; last byte: 0xC2", json::type_error&);
CHECK_THROWS_AS(j.dump(1, ' ', false, json::error_handler_t::strict), json::type_error&);
CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::ignore) == "\"123\"");
CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"123\xEF\xBF\xBD\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"123\\ufffd\"");
CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == "\"123\xC2\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::keep) == "\"123\xC2\"");
}

SECTION("unexpected character")
Expand All @@ -107,9 +113,14 @@ TEST_CASE("serialization")

CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] invalid UTF-8 byte at index 5: 0x34", json::type_error&);
CHECK_THROWS_AS(j.dump(1, ' ', false, json::error_handler_t::strict), json::type_error&);

// see pending discussion at #4452
CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123456\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::ignore) == "\"123456\"");
CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"123\xEF\xBF\xBD\x34\x35\x36\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"123\\ufffd456\"");
CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == "\"123\xF1\xB0\x34\x35\x36\"");
CHECK(j.dump(-1, ' ', true, json::error_handler_t::keep) == "\"123\xF1\xB0\x34\x35\x36\"");
}

SECTION("U+FFFD Substitution of Maximal Subparts")
Expand Down
5 changes: 5 additions & 0 deletions tests/src/unit-unicode2.cpp
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Expand Up @@ -74,6 +74,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
static std::string s_replaced2;
static std::string s_replaced_ascii;
static std::string s_replaced2_ascii;
static std::string s_kept;

// dumping with ignore/replace must not throw in any case
s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
Expand All @@ -84,6 +85,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);

if (success_expected)
{
Expand All @@ -105,6 +107,9 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
}

// check if the string is unchanged (ignoring the quotes) if error_handler_t::keep is used
CHECK(json_string == s_kept.substr(1, json_string.size()));

// check that prefix and suffix are preserved
CHECK(s_ignored2.substr(1, 3) == "abc");
CHECK(s_ignored2.substr(s_ignored2.size() - 4, 3) == "xyz");
Expand Down
5 changes: 5 additions & 0 deletions tests/src/unit-unicode3.cpp
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Expand Up @@ -74,6 +74,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
static std::string s_replaced2;
static std::string s_replaced_ascii;
static std::string s_replaced2_ascii;
static std::string s_kept;

// dumping with ignore/replace must not throw in any case
s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
Expand All @@ -84,6 +85,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);

if (success_expected)
{
Expand All @@ -105,6 +107,9 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
}

// check if the string is unchanged (ignoring the quotes) if error_handler_t::keep is used
CHECK(json_string == s_kept.substr(1, json_string.size()));

// check that prefix and suffix are preserved
CHECK(s_ignored2.substr(1, 3) == "abc");
CHECK(s_ignored2.substr(s_ignored2.size() - 4, 3) == "xyz");
Expand Down
5 changes: 5 additions & 0 deletions tests/src/unit-unicode4.cpp
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Expand Up @@ -74,6 +74,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
static std::string s_replaced2;
static std::string s_replaced_ascii;
static std::string s_replaced2_ascii;
static std::string s_kept;

// dumping with ignore/replace must not throw in any case
s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
Expand All @@ -84,6 +85,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);

if (success_expected)
{
Expand All @@ -105,6 +107,9 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
}

// check if the string is unchanged (ignoring the quotes) if error_handler_t::keep is used
CHECK(json_string == s_kept.substr(1, json_string.size()));

// check that prefix and suffix are preserved
CHECK(s_ignored2.substr(1, 3) == "abc");
CHECK(s_ignored2.substr(s_ignored2.size() - 4, 3) == "xyz");
Expand Down
5 changes: 5 additions & 0 deletions tests/src/unit-unicode5.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
static std::string s_replaced2;
static std::string s_replaced_ascii;
static std::string s_replaced2_ascii;
static std::string s_kept;

// dumping with ignore/replace must not throw in any case
s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
Expand All @@ -84,6 +85,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);

if (success_expected)
{
Expand All @@ -105,6 +107,9 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
}

// check if the string is unchanged (ignoring the quotes) if error_handler_t::keep is used
CHECK(json_string == s_kept.substr(1, json_string.size()));

// check that prefix and suffix are preserved
CHECK(s_ignored2.substr(1, 3) == "abc");
CHECK(s_ignored2.substr(s_ignored2.size() - 4, 3) == "xyz");
Expand Down
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