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Merge iterator+sentinel overloads and fix ambiguity/CI issues

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Address PR review feedback and CI failures:

- Merge the separate same-type and sentinel-type iterator overloads of
  parse(), accept(), sax_parse(), and the five from_* binary deserializers
  into a single overload with SentinelType defaulted to IteratorType,
  as suggested in review. Applied the same simplification to the
  detail::input_adapter() free functions.
- Fix a latent ambiguity: some compilers (e.g. GCC 4.8) unreliably SFINAE
  the operator!= detection for std::nullptr_t against container/string
  types, making calls like parse(s, nullptr, ...) ambiguous with the
  compatible-input overload. can_compare_ne now explicitly excludes
  std::nullptr_t as a SentinelType.
- Use a named enable_if_t template parameter instead of an unnamed
  function parameter for the SFINAE guard, fixing a clang-tidy
  hicpp-named-parameter/readability-named-parameter failure.
- Update parse.md, accept.md, sax_parse.md, and the five from_*.md pages
  to document the merged overload instead of separate (2)/(3) overloads,
  also fixing an over-160-char line that broke the documentation
  style_check CI job.
- Rework the BSON iterator+sentinel test to parse a BSON file already
  present in the test suite instead of writing/deleting a temp file.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-07-10 23:15:17 +02:00
parent 2269656bc6
commit 146e5e0bc7
12 changed files with 147 additions and 460 deletions
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include/nlohmann/detail/input/input_adapters.hpp
+17 -13
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@@ -491,10 +491,21 @@ struct can_compare_ne_reversed < IteratorType, SentinelType,
: std::true_type {};
template<typename IteratorType, typename SentinelType>
struct can_compare_ne : std::integral_constant < bool,
struct can_compare_ne_either_order : std::integral_constant < bool,
can_compare_ne_impl<IteratorType, SentinelType>::value ||
can_compare_ne_reversed<IteratorType, SentinelType>::value > {};
// std::nullptr_t is excluded explicitly: a literal `nullptr` passed as a
// trailing default argument (e.g. parse(s, nullptr, ...)) must never be
// mistaken for a sentinel, and some compilers (e.g. GCC 4.8) unreliably
// SFINAE the `operator!=` detection above for std::nullptr_t against
// container/string types, which would otherwise make such calls ambiguous
// with the compatible-input overload.
template<typename IteratorType, typename SentinelType>
struct can_compare_ne : std::integral_constant < bool,
!std::is_same<SentinelType, std::nullptr_t>::value &&
can_compare_ne_either_order<IteratorType, SentinelType>::value > {};
template<typename T>
struct is_iterator_of_multibyte
{
@@ -520,19 +531,12 @@ struct iterator_input_adapter_factory<IteratorType, SentinelType, enable_if_t<is
}
};
// General purpose iterator-based input (same-type iterators)
template<typename IteratorType>
typename iterator_input_adapter_factory<IteratorType, IteratorType>::adapter_type input_adapter(IteratorType first, IteratorType last)
{
using factory_type = iterator_input_adapter_factory<IteratorType, IteratorType>;
return factory_type::create(first, last);
}
// General purpose iterator-based input (iterator+sentinel pair with different types)
// Only enable for types that can be compared with !=
template < typename IteratorType, typename SentinelType,
// General purpose iterator-based input (iterator+sentinel pair; SentinelType
// defaults to IteratorType for the common same-type case, but may differ for
// C++20 ranges-style iterator+sentinel pairs). Only enable for types that can
// be compared with !=.
template < typename IteratorType, typename SentinelType = IteratorType,
typename = typename std::enable_if <
!std::is_same<IteratorType, SentinelType>::value &&
can_compare_ne<IteratorType, SentinelType>::value >::type >
typename iterator_input_adapter_factory<IteratorType, SentinelType>::adapter_type input_adapter(IteratorType first, SentinelType last)
{