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Extend value to arrays when using JSON pointers (#5223)

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* ✨ extend value to arrays when using JSON pointers

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 💚 avoid exceptions

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 💚 avoid exceptions

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-07-02 06:35:35 +02:00
committed by GitHub
parent 730b57775d
commit ca49ab6123
7 changed files with 271 additions and 53 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/nlohmann/detail/json_pointer.hpp
+92 -4
View File
@@ -480,8 +480,14 @@ class json_pointer
") is out of range"), ptr));
}
// note: at performs range check
ptr = &ptr->at(array_index<BasicJsonType>(reference_token));
const auto idx = array_index<BasicJsonType>(reference_token);
// Bounds check before access to avoid exception with JSON_NOEXCEPTION
if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
{
JSON_THROW(detail::out_of_range::create(401, detail::concat(
"array index ", std::to_string(idx), " is out of range"), ptr));
}
ptr = &ptr->operator[](idx);
break;
}
@@ -587,8 +593,14 @@ class json_pointer
") is out of range"), ptr));
}
// note: at performs range check
ptr = &ptr->at(array_index<BasicJsonType>(reference_token));
const auto idx = array_index<BasicJsonType>(reference_token);
// Bounds check before access to avoid exception with JSON_NOEXCEPTION
if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
{
JSON_THROW(detail::out_of_range::create(401, detail::concat(
"array index ", std::to_string(idx), " is out of range"), ptr));
}
ptr = &ptr->operator[](idx);
break;
}
@@ -608,6 +620,82 @@ class json_pointer
return *ptr;
}
/*!
@brief return a pointer to the pointed to value, or `nullptr` if the
pointer cannot be resolved because a key is missing, an array
index is out of range, or the array index is "-"
@note unlike get_checked(), this never throws for those cases, so it
can be used to implement a non-throwing fallback (e.g. value())
that also works when exceptions are disabled
@throw parse_error.106 if an array index begins with '0'
@throw parse_error.109 if an array index was not a number
*/
template<typename BasicJsonType>
const BasicJsonType* get_checked_or_null(const BasicJsonType* ptr) const
{
for (const auto& reference_token : reference_tokens)
{
switch (ptr->type())
{
case detail::value_t::object:
{
const auto it = ptr->find(reference_token);
if (JSON_HEDLEY_UNLIKELY(it == ptr->end()))
{
return nullptr;
}
ptr = &*it;
break;
}
case detail::value_t::array:
{
if (JSON_HEDLEY_UNLIKELY(reference_token == "-"))
{
// "-" always fails the range check
return nullptr;
}
// may throw parse_error.106/109 for a malformed index; an
// index that is syntactically valid but cannot be
// represented (out_of_range.404/410) is treated like an
// out-of-range index below
typename BasicJsonType::size_type idx{};
JSON_TRY
{
idx = array_index<BasicJsonType>(reference_token);
}
JSON_INTERNAL_CATCH (detail::out_of_range&)
{
return nullptr;
}
if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
{
return nullptr;
}
ptr = &ptr->operator[](idx);
break;
}
case detail::value_t::null:
case detail::value_t::string:
case detail::value_t::boolean:
case detail::value_t::number_integer:
case detail::value_t::number_unsigned:
case detail::value_t::number_float:
case detail::value_t::binary:
case detail::value_t::discarded:
default:
return nullptr;
}
}
return ptr;
}
/*!
@throw parse_error.106 if an array index begins with '0'
@throw parse_error.109 if an array index was not a number
include/nlohmann/json.hpp
+14 -16
View File
@@ -2393,19 +2393,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
&& !std::is_same<value_t, detail::uncvref_t<ValueType>>::value, int > = 0 >
ValueType value(const json_pointer& ptr, const ValueType& default_value) const
{
// value only works for objects
if (JSON_HEDLEY_LIKELY(is_object()))
// value only works for arrays and objects
if (JSON_HEDLEY_LIKELY(is_structured()))
{
// If the pointer resolves to a value, return it. Otherwise, return
// 'default_value'.
JSON_TRY
const auto* res = ptr.get_checked_or_null(this);
if (JSON_HEDLEY_LIKELY(res != nullptr))
{
return ptr.get_checked(this).template get<ValueType>();
}
JSON_INTERNAL_CATCH (out_of_range&)
{
return default_value;
return res->template get<ValueType>();
}
return default_value;
}
JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));
@@ -2419,19 +2418,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
&& !std::is_same<value_t, detail::uncvref_t<ValueType>>::value, int > = 0 >
ReturnType value(const json_pointer& ptr, ValueType && default_value) const
{
// value only works for objects
if (JSON_HEDLEY_LIKELY(is_object()))
// value only works for arrays and objects
if (JSON_HEDLEY_LIKELY(is_structured()))
{
// If the pointer resolves to a value, return it. Otherwise, return
// 'default_value'.
JSON_TRY
const auto* res = ptr.get_checked_or_null(this);
if (JSON_HEDLEY_LIKELY(res != nullptr))
{
return ptr.get_checked(this).template get<ReturnType>();
}
JSON_INTERNAL_CATCH (out_of_range&)
{
return std::forward<ValueType>(default_value);
return res->template get<ReturnType>();
}
return std::forward<ValueType>(default_value);
}
JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));