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json_view: pass accept()'s validate-only request as a parameter

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Address review of #5970:
- build() takes validate_only as an argument; the validate_only members of
  document_data and basic_json_document are removed, so neither grows
- the internal read path takes an on_error mode (discard, raise, validate)
  instead of allow_exceptions; accept() calls it with on_error::validate
- build_with() has no default for Store
- drop the unneeded static_casts in push_node()
- name the NulIsEnd argument so astyle keeps build<...> intact
- explain in the docs and code why comments/trailing commas keep the index

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann committed 2026-10-31 11:14:50 +01:00
1 parent 9ba25b1b66
commit 83322fe0ad
6 files changed
+109 -79
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single_include/nlohmann/json_view.hpp
Generated
+51 -38
View File
@@ -389,7 +389,6 @@ struct document_data
std::vector<std::uint32_t> large_objects; ///< positions of the objects to index (noted while parsing)
std::array<const char*, 4> base = {{nullptr, nullptr, nullptr, nullptr}}; ///< string bases: source, arena, edit arena, unused (indexed by flags & node_flags::storage)
bool discarded = true;
bool validate_only = false; ///< accept(): build() checks the text and stores no nodes (next to `discarded`: no member moves)
/// The storage of edits (editable documents only; see edit_storage.hpp).
/// No edit moves or resizes the parsed index, and the nodes of values
@@ -2294,11 +2293,6 @@ indent_done:
{
// accept(): nothing is stored, so what computes the arguments is not run either. base and out stay
// null: their difference, which open() takes, is 0.
static_cast<void>(k);
static_cast<void>(flags);
static_cast<void>(extra);
static_cast<void>(off);
static_cast<void>(second);
return out;
}
if (NLOHMANN_VIEW_UNLIKELY(out == cap))
@@ -2539,7 +2533,7 @@ indent_done:
};
/// run the builder with compile-time options
template<typename FloatType, bool Comments, bool TrailingCommas, bool NulIsEnd, bool Store = true>
template<typename FloatType, bool Comments, bool TrailingCommas, bool NulIsEnd, bool Store>
inline bool build_with(document_data& d, const char* src, std::size_t size, bool sentinel, parse_failure& failure)
{
if (sentinel)
@@ -2556,22 +2550,27 @@ inline bool build_with(document_data& d, const char* src, std::size_t size, bool
}
/// sentinel: src[size] is readable and 0 (e.g. std::string); FloatType: the
/// number_float_t of the document
/// number_float_t of the document; validate_only: accept(), only the result is
/// used
template<typename FloatType, bool NulIsEnd>
inline bool build(document_data& d, const char* src, std::size_t size, bool comments, bool trailing_commas, bool sentinel, parse_failure& failure)
inline bool build(document_data& d, const char* src, std::size_t size, bool comments, bool trailing_commas, bool sentinel, bool validate_only,
parse_failure& failure)
{
if (d.validate_only && !comments && !trailing_commas)
if (validate_only && !comments && !trailing_commas)
{
// accept() of plain JSON: nothing is stored (the other option sets keep the builder that stores)
// accept() of plain JSON: nothing is stored. The other option sets
// could skip the stores just as well; they keep the builder that
// stores only so that there are two more instantiations of the parse
// loop, not eight.
return build_with<FloatType, false, false, NulIsEnd, false>(d, src, size, sentinel, failure);
}
if (comments)
{
return trailing_commas ? build_with<FloatType, true, true, NulIsEnd>(d, src, size, sentinel, failure)
: build_with<FloatType, true, false, NulIsEnd>(d, src, size, sentinel, failure);
return trailing_commas ? build_with<FloatType, true, true, NulIsEnd, true>(d, src, size, sentinel, failure)
: build_with<FloatType, true, false, NulIsEnd, true>(d, src, size, sentinel, failure);
}
return trailing_commas ? build_with<FloatType, false, true, NulIsEnd>(d, src, size, sentinel, failure)
: build_with<FloatType, false, false, NulIsEnd>(d, src, size, sentinel, failure);
return trailing_commas ? build_with<FloatType, false, true, NulIsEnd, true>(d, src, size, sentinel, failure)
: build_with<FloatType, false, false, NulIsEnd, true>(d, src, size, sentinel, failure);
}
} // namespace view
@@ -10211,7 +10210,7 @@ class basic_json_document
const bool ignore_trailing_commas = false)
{
basic_json_document d;
d.read_range(first, last, allow_exceptions, ignore_comments, ignore_trailing_commas);
d.read_range(first, last, error_mode(allow_exceptions), ignore_comments, ignore_trailing_commas);
return d;
}
@@ -10226,7 +10225,7 @@ class basic_json_document
basic_json_document d;
std::string buf;
append_input(buf, std::forward<InputType>(input));
d.build_owned(std::move(buf), allow_exceptions, ignore_comments, ignore_trailing_commas);
d.build_owned(std::move(buf), error_mode(allow_exceptions), ignore_comments, ignore_trailing_commas);
return d;
}
@@ -10239,8 +10238,8 @@ class basic_json_document
static bool accept(InputType&& input, const bool ignore_comments = false, const bool ignore_trailing_commas = false)
{
basic_json_document d;
d.m_validate_only = true; // (nothing is stored: only the result is used)
d.read(std::forward<InputType>(input), false, ignore_comments, ignore_trailing_commas);
d.read_kind(std::forward<InputType>(input), on_error::validate, ignore_comments, ignore_trailing_commas,
std::integral_constant<detail::view::input_kind, detail::view::classify_input<InputType>::value> {});
return !d.is_discarded();
}
@@ -10256,7 +10255,7 @@ class basic_json_document
const bool ignore_comments = false,
const bool ignore_trailing_commas = false)
{
read_kind(std::forward<InputType>(input), allow_exceptions, ignore_comments, ignore_trailing_commas,
read_kind(std::forward<InputType>(input), error_mode(allow_exceptions), ignore_comments, ignore_trailing_commas,
std::integral_constant<detail::view::input_kind, detail::view::classify_input<InputType>::value> {});
}
@@ -10615,6 +10614,22 @@ class basic_json_document
return idx;
}
/// what a failed parse does
enum class on_error : std::uint8_t
{
discard, ///< the document is discarded
raise, ///< parse_error is thrown
validate ///< accept(): the document is discarded, and no node is stored while parsing
};
static on_error error_mode(bool allow_exceptions) noexcept
{
return allow_exceptions ? on_error::raise : on_error::discard;
}
/// NulIsEnd of the builder: a null byte ends the input unless strict_nul_handling
static constexpr bool nul_is_end = !detail::abi_config::strict_nul_handling;
/// create the storage (sized for the input) on first use
void ensure_data(const char* src, std::size_t size)
{
@@ -10626,7 +10641,7 @@ class basic_json_document
/// parse a buffer the document takes ownership of (it replaces the
/// previous owned copy)
void build_owned(std::string&& buf, bool allow_exceptions, bool comments, bool trailing_commas)
void build_owned(std::string&& buf, on_error allow_exceptions, bool comments, bool trailing_commas)
{
ensure_data(buf.data(), buf.size());
m_data->owned = std::move(buf);
@@ -10636,7 +10651,7 @@ class basic_json_document
/// parse a copy of the input; the copy is appended to the cleared owned
/// buffer, so that its capacity is reused
template<typename T>
void build_copy(T&& input, bool allow_exceptions, bool comments, bool trailing_commas)
void build_copy(T&& input, on_error allow_exceptions, bool comments, bool trailing_commas)
{
if (!m_data)
{
@@ -10657,7 +10672,7 @@ class basic_json_document
}
/// sentinel: src[size] is readable and 0 (std::string, C strings)
void build(const char* src, std::size_t size, bool allow_exceptions, bool comments, bool trailing_commas, bool owned, bool sentinel)
void build(const char* src, std::size_t size, on_error allow_exceptions, bool comments, bool trailing_commas, bool owned, bool sentinel)
{
ensure_data(src, size);
document_data& d = *m_data;
@@ -10684,9 +10699,8 @@ class basic_json_document
}
else
{
d.validate_only = m_validate_only;
ok = detail::view::build < typename BasicJsonType::number_float_t, !detail::abi_config::strict_nul_handling > (d, src, size, comments, trailing_commas, sentinel, failure);
d.validate_only = false;
ok = detail::view::build<typename BasicJsonType::number_float_t, nul_is_end>(d, src, size, comments, trailing_commas, sentinel,
allow_exceptions == on_error::validate, failure);
}
if (NLOHMANN_VIEW_LIKELY(ok))
{
@@ -10699,7 +10713,7 @@ class basic_json_document
return;
}
std::vector<std::uint32_t>().swap(d.large_objects);
if (allow_exceptions)
if (allow_exceptions == on_error::raise)
{
detail::view::throw_parse_failure<BasicJsonType>(failure, src, size, comments, trailing_commas);
}
@@ -10707,13 +10721,13 @@ class basic_json_document
// --- input dispatch (see detail::view::input_kind) ---
void read_kind(std::string&& s, bool ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::move_string> /*unused*/)
void read_kind(std::string&& s, on_error ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::move_string> /*unused*/)
{
build_owned(std::move(s), ae, c, tc);
}
template<typename CharT>
void read_kind(CharT* s, bool ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::c_string> /*unused*/)
void read_kind(CharT* s, on_error ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::c_string> /*unused*/)
{
if (s == nullptr)
{
@@ -10727,7 +10741,7 @@ class basic_json_document
}
template<typename Array>
void read_kind(Array& a, bool ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::char_array> /*unused*/)
void read_kind(Array& a, on_error ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::char_array> /*unused*/)
{
using CharT = typename std::remove_cv<typename std::remove_extent<Array>::type>::type;
const std::size_t n = std::extent<Array>::value;
@@ -10738,7 +10752,7 @@ class basic_json_document
}
template<typename T>
void read_kind(const T& s, bool ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::borrow_range> /*unused*/)
void read_kind(const T& s, on_error ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::borrow_range> /*unused*/)
{
// std::basic_string guarantees data()[size()] == 0: use it as sentinel
const auto size = static_cast<std::size_t>(s.size());
@@ -10747,13 +10761,13 @@ class basic_json_document
}
template<typename T>
void read_kind(const T& s, bool ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::copy_range> /*unused*/)
void read_kind(const T& s, on_error ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::copy_range> /*unused*/)
{
build_copy(s, ae, c, tc);
}
template<typename CharT>
void read_kind(CharT* s, bool ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::wide_c_string> /*unused*/)
void read_kind(CharT* s, on_error ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::wide_c_string> /*unused*/)
{
if (s == nullptr)
{
@@ -10765,13 +10779,13 @@ class basic_json_document
}
template<typename T>
void read_kind(T&& input, bool ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::adapter> /*unused*/)
void read_kind(T&& input, on_error ae, bool c, bool tc, std::integral_constant<input_kind, input_kind::adapter> /*unused*/)
{
build_copy(std::forward<T>(input), ae, c, tc);
}
template<typename IteratorType>
void read_range(IteratorType first, IteratorType last, bool ae, bool c, bool tc)
void read_range(IteratorType first, IteratorType last, on_error ae, bool c, bool tc)
{
using value_type = typename std::remove_cv<typename std::iterator_traits<IteratorType>::value_type>::type;
// borrow the range where the library's input adapter scans it as one
@@ -10782,14 +10796,14 @@ class basic_json_document
}
template<typename IteratorType>
void read_range_impl(IteratorType first, IteratorType last, bool ae, bool c, bool tc, std::true_type /*contiguous bytes*/)
void read_range_impl(IteratorType first, IteratorType last, on_error ae, bool c, bool tc, std::true_type /*contiguous bytes*/)
{
const auto size = static_cast<std::size_t>(std::distance(first, last));
build(size == 0 ? "" : reinterpret_cast<const char*>(&*first), size, ae, c, tc, false, size == 0); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
}
template<typename IteratorType>
void read_range_impl(IteratorType first, IteratorType last, bool ae, bool c, bool tc, std::false_type /*other*/)
void read_range_impl(IteratorType first, IteratorType last, on_error ae, bool c, bool tc, std::false_type /*other*/)
{
build_copy(detail::view::make_adapter_input(detail::input_adapter(first, last)), ae, c, tc);
}
@@ -10847,7 +10861,6 @@ class basic_json_document
}
std::unique_ptr<document_data, document_data::deleter> m_data{}; // NOLINT(readability-redundant-member-init)
bool m_validate_only = false; ///< set by accept(): build() stores no nodes
};
/*!