Pass alt_string's std::string constructor argument by value (clang-tidy modernize-pass-by-value)

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

.github/workflows/check_amalgamation.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -34,7 +34,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/cifuzz.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+      uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
       with:
         egress-policy: audit
 

.github/workflows/codeql-analysis.yml

@@ -27,7 +27,7 @@ jobs:
 
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+      uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
       with:
         egress-policy: audit
 

.github/workflows/comment_check_amalgamation.yml

@@ -19,7 +19,7 @@ jobs:
       pull-requests: write
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/dependency-review.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/flawfinder.yml

@@ -27,7 +27,7 @@ jobs:
       security-events: write
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/labeler.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/publish_documentation.yml

@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/scorecards.yml

@@ -36,7 +36,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/semgrep.yml

@@ -32,7 +32,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/stale.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

.github/workflows/ubuntu.yml

@@ -35,7 +35,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -60,7 +60,7 @@ jobs:
         target: [ci_test_amalgamation, ci_test_single_header, ci_cppcheck, ci_cpplint, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata, ci_reuse_compliance, ci_test_valgrind]
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -118,7 +118,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -369,7 +369,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -392,7 +392,7 @@ jobs:
         target: [ci_test_examples, ci_test_build_documentation]
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

include/nlohmann/detail/input/lexer.hpp

@@ -149,11 +149,10 @@ class lexer : public lexer_base<BasicJsonType>
   public:
     using token_type = typename lexer_base<BasicJsonType>::token_type;
 
-    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false, bool discard_number_values_ = false) noexcept
+    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false) noexcept
         : ia(std::move(adapter))
         , ignore_comments(ignore_comments_)
         , decimal_point_char(static_cast<char_int_type>(get_decimal_point()))
-        , discard_number_values(discard_number_values_)
     {}
 
     // deleted because of pointer members
@@ -1280,58 +1279,6 @@ scan_number_done:
         // we are done scanning a number)
         unget();
 
-        // If the caller does not need the converted value (only whether the
-        // input is syntactically valid; see json_sax_acceptor/accept()), an
-        // unsigned/integer token can be reported without calling
-        // strtoull()/strtoll() at all, *provided* we can already tell from
-        // the digit count alone that the conversion cannot overflow 64 bits.
-        // Such tokens are always finite and are accepted unconditionally by
-        // the parser regardless of their actual value (parser::sax_parse_internal()
-        // never checks finiteness for value_unsigned/value_integer), so the
-        // classification below is all that is needed.
-        //
-        // A decimal number with up to 18 digits is always representable in
-        // both std::uint64_t and std::int64_t (18 nines is ~1e18, well below
-        // both UINT64_MAX ~1.8e19 and INT64_MAX ~9.2e18), so strtoull()/strtoll()
-        // could not have set errno to ERANGE for it. Numbers with more digits
-        // (rare in practice) fall through to the exact code below, unchanged,
-        // so their handling -- including reclassification to value_float when
-        // the value overflows 64 bits, and rejection when it is not even
-        // finite as a double -- is bit-for-bit identical to before this
-        // optimization.
-        //
-        // Note this reasons about std::uint64_t/std::int64_t, not about
-        // number_unsigned_t/number_integer_t (BasicJsonType's own, possibly
-        // narrower, template parameters -- e.g. std::uint32_t). That is fine
-        // *only* because discard_number_values is exclusively set by
-        // accept() (see json.hpp), and accept() always parses through the
-        // library's own json_sax_acceptor -- never a user-supplied SAX
-        // consumer -- whose number_unsigned()/number_integer()/number_float()
-        // callbacks unconditionally discard their argument and return true.
-        // So for every caller that can reach this branch, neither the token
-        // classification below nor the eventual (possibly narrowed, and on
-        // this fast path left stale/unset) value_unsigned/value_integer is
-        // ever consulted -- an unsigned/integer token is accepted outright,
-        // and even a >18-digit token that this fast path deliberately falls
-        // through for is, once reclassified to value_float, still finite
-        // (and thus accepted) for any digit count that fits in number_unsigned_t
-        // or number_integer_t regardless of that type's width. If this
-        // function is ever taught to run with discard_number_values true for
-        // a caller that *does* read the converted value, this reasoning (and
-        // the fast path below) would need to be revisited.
-        if (discard_number_values)
-        {
-            constexpr std::size_t safe_digit_count = 18;
-            if (number_type == token_type::value_unsigned && token_buffer.size() <= safe_digit_count)
-            {
-                return token_type::value_unsigned;
-            }
-            if (number_type == token_type::value_integer && token_buffer.size() - 1 <= safe_digit_count)
-            {
-                return token_type::value_integer;
-            }
-        }
-
         char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
         errno = 0;
 
@@ -1807,13 +1754,6 @@ scan_number_done:
     const char_int_type decimal_point_char = '.';
     /// the position of the decimal point in the input
     std::size_t decimal_point_position = std::string::npos;
-
-    /// whether the caller (e.g. accept()/json_sax_acceptor) only needs the
-    /// token classification and never looks at the converted numeric value;
-    /// when set, scan_number() may skip strtoull()/strtoll() for
-    /// value_unsigned/value_integer tokens whose digit count guarantees they
-    /// fit into 64 bits (see scan_number())
-    const bool discard_number_values = false;
 };
 
 }  // namespace detail

include/nlohmann/detail/input/parser.hpp

@@ -72,10 +72,9 @@ class parser
                     parser_callback_t<BasicJsonType> cb = nullptr,
                     const bool allow_exceptions_ = true,
                     const bool ignore_comments = false,
-                    const bool ignore_trailing_commas_ = false,
+                    const bool ignore_trailing_commas_ = false)
-                    const bool discard_number_values_ = false)
         : callback(std::move(cb))
-        , m_lexer(std::move(adapter), ignore_comments, discard_number_values_)
+        , m_lexer(std::move(adapter), ignore_comments)
         , allow_exceptions(allow_exceptions_)
         , ignore_trailing_commas(ignore_trailing_commas_)
     {

include/nlohmann/json.hpp

@@ -164,12 +164,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         detail::parser_callback_t<basic_json>cb = nullptr,
         const bool allow_exceptions = true,
         const bool ignore_comments = false,
-        const bool ignore_trailing_commas = false,
+        const bool ignore_trailing_commas = false
-        const bool discard_number_values = false
     )
     {
         return ::nlohmann::detail::parser<basic_json, InputAdapterType>(std::move(adapter),
-               std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas, discard_number_values);
+               std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
     }
 
   private:
@@ -4134,7 +4133,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return parser(detail::input_adapter(std::forward<InputType>(i)), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
+        return parser(detail::input_adapter(std::forward<InputType>(i)), nullptr, false, ignore_comments, ignore_trailing_commas).accept(true);
     }
 
     /// @brief check if the input is valid JSON (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -4145,7 +4144,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return parser(detail::input_adapter(std::move(first), std::move(last)), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
+        return parser(detail::input_adapter(std::move(first), std::move(last)), nullptr, false, ignore_comments, ignore_trailing_commas).accept(true);
     }
 
     JSON_HEDLEY_WARN_UNUSED_RESULT
@@ -4154,7 +4153,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return parser(i.get(), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
+        return parser(i.get(), nullptr, false, ignore_comments, ignore_trailing_commas).accept(true);
     }
 
     /// @brief generate SAX events

single_include/nlohmann/json.hpp

@@ -7932,11 +7932,10 @@ class lexer : public lexer_base<BasicJsonType>
   public:
     using token_type = typename lexer_base<BasicJsonType>::token_type;
 
-    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false, bool discard_number_values_ = false) noexcept
+    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false) noexcept
         : ia(std::move(adapter))
         , ignore_comments(ignore_comments_)
         , decimal_point_char(static_cast<char_int_type>(get_decimal_point()))
-        , discard_number_values(discard_number_values_)
     {}
 
     // deleted because of pointer members
@@ -9063,58 +9062,6 @@ scan_number_done:
         // we are done scanning a number)
         unget();
 
-        // If the caller does not need the converted value (only whether the
-        // input is syntactically valid; see json_sax_acceptor/accept()), an
-        // unsigned/integer token can be reported without calling
-        // strtoull()/strtoll() at all, *provided* we can already tell from
-        // the digit count alone that the conversion cannot overflow 64 bits.
-        // Such tokens are always finite and are accepted unconditionally by
-        // the parser regardless of their actual value (parser::sax_parse_internal()
-        // never checks finiteness for value_unsigned/value_integer), so the
-        // classification below is all that is needed.
-        //
-        // A decimal number with up to 18 digits is always representable in
-        // both std::uint64_t and std::int64_t (18 nines is ~1e18, well below
-        // both UINT64_MAX ~1.8e19 and INT64_MAX ~9.2e18), so strtoull()/strtoll()
-        // could not have set errno to ERANGE for it. Numbers with more digits
-        // (rare in practice) fall through to the exact code below, unchanged,
-        // so their handling -- including reclassification to value_float when
-        // the value overflows 64 bits, and rejection when it is not even
-        // finite as a double -- is bit-for-bit identical to before this
-        // optimization.
-        //
-        // Note this reasons about std::uint64_t/std::int64_t, not about
-        // number_unsigned_t/number_integer_t (BasicJsonType's own, possibly
-        // narrower, template parameters -- e.g. std::uint32_t). That is fine
-        // *only* because discard_number_values is exclusively set by
-        // accept() (see json.hpp), and accept() always parses through the
-        // library's own json_sax_acceptor -- never a user-supplied SAX
-        // consumer -- whose number_unsigned()/number_integer()/number_float()
-        // callbacks unconditionally discard their argument and return true.
-        // So for every caller that can reach this branch, neither the token
-        // classification below nor the eventual (possibly narrowed, and on
-        // this fast path left stale/unset) value_unsigned/value_integer is
-        // ever consulted -- an unsigned/integer token is accepted outright,
-        // and even a >18-digit token that this fast path deliberately falls
-        // through for is, once reclassified to value_float, still finite
-        // (and thus accepted) for any digit count that fits in number_unsigned_t
-        // or number_integer_t regardless of that type's width. If this
-        // function is ever taught to run with discard_number_values true for
-        // a caller that *does* read the converted value, this reasoning (and
-        // the fast path below) would need to be revisited.
-        if (discard_number_values)
-        {
-            constexpr std::size_t safe_digit_count = 18;
-            if (number_type == token_type::value_unsigned && token_buffer.size() <= safe_digit_count)
-            {
-                return token_type::value_unsigned;
-            }
-            if (number_type == token_type::value_integer && token_buffer.size() - 1 <= safe_digit_count)
-            {
-                return token_type::value_integer;
-            }
-        }
-
         char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
         errno = 0;
 
@@ -9590,13 +9537,6 @@ scan_number_done:
     const char_int_type decimal_point_char = '.';
     /// the position of the decimal point in the input
     std::size_t decimal_point_position = std::string::npos;
-
-    /// whether the caller (e.g. accept()/json_sax_acceptor) only needs the
-    /// token classification and never looks at the converted numeric value;
-    /// when set, scan_number() may skip strtoull()/strtoll() for
-    /// value_unsigned/value_integer tokens whose digit count guarantees they
-    /// fit into 64 bits (see scan_number())
-    const bool discard_number_values = false;
 };
 
 }  // namespace detail
@@ -14103,10 +14043,9 @@ class parser
                     parser_callback_t<BasicJsonType> cb = nullptr,
                     const bool allow_exceptions_ = true,
                     const bool ignore_comments = false,
-                    const bool ignore_trailing_commas_ = false,
+                    const bool ignore_trailing_commas_ = false)
-                    const bool discard_number_values_ = false)
         : callback(std::move(cb))
-        , m_lexer(std::move(adapter), ignore_comments, discard_number_values_)
+        , m_lexer(std::move(adapter), ignore_comments)
         , allow_exceptions(allow_exceptions_)
         , ignore_trailing_commas(ignore_trailing_commas_)
     {
@@ -21653,12 +21592,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         detail::parser_callback_t<basic_json>cb = nullptr,
         const bool allow_exceptions = true,
         const bool ignore_comments = false,
-        const bool ignore_trailing_commas = false,
+        const bool ignore_trailing_commas = false
-        const bool discard_number_values = false
                                  )
     {
         return ::nlohmann::detail::parser<basic_json, InputAdapterType>(std::move(adapter),
-            std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas, discard_number_values);
+            std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
     }
 
   private:
@@ -25623,7 +25561,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return parser(detail::input_adapter(std::forward<InputType>(i)), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
+        return parser(detail::input_adapter(std::forward<InputType>(i)), nullptr, false, ignore_comments, ignore_trailing_commas).accept(true);
     }
 
     /// @brief check if the input is valid JSON (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -25634,7 +25572,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return parser(detail::input_adapter(std::move(first), std::move(last)), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
+        return parser(detail::input_adapter(std::move(first), std::move(last)), nullptr, false, ignore_comments, ignore_trailing_commas).accept(true);
     }
 
     JSON_HEDLEY_WARN_UNUSED_RESULT
@@ -25643,7 +25581,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return parser(i.get(), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
+        return parser(i.get(), nullptr, false, ignore_comments, ignore_trailing_commas).accept(true);
     }
 
     /// @brief generate SAX events

tests/src/unit-class_parser.cpp

@@ -930,98 +930,6 @@ TEST_CASE("parser class")
                 CHECK(accept_helper("+1") == false);
                 CHECK(accept_helper("+0") == false);
             }
-
-            SECTION("issue #5411 - skip conversion when accept() does not need the numeric value")
-            {
-                // lexer::scan_number() may skip strtoull()/strtoll() for
-                // value_unsigned/value_integer tokens when the caller (e.g.
-                // json::accept()) does not need the converted value, as long
-                // as the digit count alone guarantees no 64-bit overflow (see
-                // the "safe_digit_count" fast path in scan_number()). This
-                // differential test checks that json::accept() (which enables
-                // the fast path) and json::parse() (which never does) always
-                // agree, over a corpus that exercises both the fast path
-                // (<=18 digits) and the untouched, exact fallback path (>=19
-                // digits) -- including reclassification of huge digit-only
-                // integers to a (possibly non-finite) floating-point value.
-                const std::vector<std::pair<std::string, bool>> cases =
-                {
-                    // normal small/large integers, both signs
-                    {"0", true}, {"1", true}, {"-1", true}, {"42", true}, {"-42", true},
-                    {"123456789", true}, {"-123456789", true},
-
-                    // digit-count boundary around the 18-digit safe cutoff (both signs)
-                    {std::string(17, '9'), true},
-                    {std::string(18, '9'), true},
-                    {std::string(19, '9'), true},
-                    {std::string(20, '9'), true},
-                    {"-" + std::string(17, '9'), true},
-                    {"-" + std::string(18, '9'), true},
-                    {"-" + std::string(19, '9'), true},
-                    {"-" + std::string(20, '9'), true},
-
-                    // 64-bit boundaries
-                    {"9223372036854775807", true},    // INT64_MAX
-                    {"-9223372036854775808", true},   // INT64_MIN
-                    {"18446744073709551615", true},   // UINT64_MAX
-                    {"18446744073709551616", true},   // UINT64_MAX + 1 (overflows uint64_t, finite double)
-
-                    // the 28-digit example from the issue: overflows uint64_t
-                    // but is finite as a double, so the scanner reclassifies
-                    // it to value_float and it is accepted
-                    {"9999999999999999999999999999", true},
-
-                    // huge digit-only integers that overflow even a double -> rejected
-                    {std::string(309, '9'), false},
-                    {std::string(400, '9'), false},
-                    {"1" + std::string(400, '0'), false},
-
-                    // 1e999 / 1e400 style overflow -> rejected
-                    {"1e999", false},
-                    {"1e400", false},
-                    {"-1e999", false},
-                    {"1E999", false},
-
-                    // values straddling DBL_MAX
-                    {"1.7976931348623157e308", true},   // <= DBL_MAX, finite
-                    {"1.7976931348623159e308", false},  // > DBL_MAX, overflows to inf
-
-                    // a mix of other valid/invalid numeric syntax
-                    {"3.14159", true},
-                    {"-0.0", true},
-                    {"1.0e10", true},
-                    {"01", false},
-                    {"-", false},
-                    {"1.", false},
-                    {"1e", false},
-                    {"+1", false},
-                };
-
-                for (const auto& c : cases)
-                {
-                    const std::string& number = c.first;
-                    const bool expected = c.second;
-                    CAPTURE(number)
-                    CAPTURE(expected)
-
-                    // accept() takes the fast path (skips conversion when possible)
-                    CHECK(json::accept(number) == expected);
-
-                    // parse() always performs the full conversion; it must agree
-                    json j;
-                    CHECK_NOTHROW(json::parser(nlohmann::detail::input_adapter(number), nullptr, false).parse(true, j));
-                    CHECK(!j.is_discarded() == expected);
-
-                    // wrap in an array so get_token() is exercised beyond the
-                    // very first (constructor-time) scan as well
-                    std::string wrapped = "[";
-                    wrapped += number;
-                    wrapped += ",";
-                    wrapped += number;
-                    wrapped += "]";
-                    CHECK(json::accept(wrapped) == expected);
-                }
-            }
         }
     }
 

tests/src/unit-ordered_json2.cpp

@@ -0,0 +1,489 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-FileCopyrightText: 2018 Vitaliy Manushkin <agri@akamo.info>
+// SPDX-License-Identifier: MIT
+
+// This file closes a test-coverage gap described in GitHub issue #5421:
+// nlohmann::ordered_json (and other non-default basic_json specializations,
+// such as the alt_string-based one from unit-alt-string.cpp) were never
+// exercised through the binary formats (CBOR/MessagePack/UBJSON/BSON/BJData)
+// or through flatten()/unflatten()/diff()/patch()/merge_patch().
+
+#include "doctest_compatibility.h"
+
+#include <nlohmann/json.hpp>
+
+#include <cstdint>
+#include <string>
+#include <utility>
+#include <vector>
+
+using nlohmann::json;
+using nlohmann::ordered_json;
+
+/////////////////////////////////////////////////////////////////////////////
+// alt_json: a second, independent copy of the custom-string_t basic_json
+// specialization defined in unit-alt-string.cpp.
+//
+// It is duplicated here (rather than shared via a header) because every
+// unit-*.cpp file in this test suite is compiled into its own standalone
+// executable (see tests/CMakeLists.txt), so there is no ODR concern in
+// having the same class name defined in multiple translation units.
+//
+// Two members had to be added relative to the original alt_string
+// (a constructor from std::string, and a find(char, pos) overload) because
+// the original type was never used with the binary writers/readers before
+// this file: BSON's array/document writer converts std::to_string() results
+// and checks for embedded NUL characters via find(char), and the UBJSON/BSON
+// high-precision-number path constructs the SAX string_t argument from a
+// std::string. Neither path is exercised anywhere else in the test suite for
+// this type, which is presumably why the gap was never noticed.
+/////////////////////////////////////////////////////////////////////////////
+
+class alt_string;
+bool operator<(const char* op1, const alt_string& op2) noexcept; // NOLINT(misc-use-internal-linkage)
+void int_to_string(alt_string& target, std::size_t value); // NOLINT(misc-use-internal-linkage)
+
+class alt_string
+{
+  public:
+    using value_type = std::string::value_type;
+
+    static constexpr auto npos = (std::numeric_limits<std::size_t>::max)();
+
+    alt_string(const char* str): str_impl(str) {}
+    alt_string(const char* str, std::size_t count): str_impl(str, count) {}
+    alt_string(std::string str): str_impl(std::move(str)) {}
+    alt_string(size_t count, char chr): str_impl(count, chr) {}
+    alt_string() = default;
+
+    alt_string& append(char ch)
+    {
+        str_impl.push_back(ch);
+        return *this;
+    }
+
+    alt_string& append(const alt_string& str)
+    {
+        str_impl.append(str.str_impl);
+        return *this;
+    }
+
+    alt_string& append(const char* s, std::size_t length)
+    {
+        str_impl.append(s, length);
+        return *this;
+    }
+
+    void push_back(char c)
+    {
+        str_impl.push_back(c);
+    }
+
+    template <typename op_type>
+    bool operator==(const op_type& op) const
+    {
+        return str_impl == op;
+    }
+
+    bool operator==(const alt_string& op) const
+    {
+        return str_impl == op.str_impl;
+    }
+
+    template <typename op_type>
+    bool operator!=(const op_type& op) const
+    {
+        return str_impl != op;
+    }
+
+    bool operator!=(const alt_string& op) const
+    {
+        return str_impl != op.str_impl;
+    }
+
+    std::size_t size() const noexcept
+    {
+        return str_impl.size();
+    }
+
+    void resize(std::size_t n)
+    {
+        str_impl.resize(n);
+    }
+
+    void resize(std::size_t n, char c)
+    {
+        str_impl.resize(n, c);
+    }
+
+    template <typename op_type>
+    bool operator<(const op_type& op) const noexcept
+    {
+        return str_impl < op;
+    }
+
+    bool operator<(const alt_string& op) const noexcept
+    {
+        return str_impl < op.str_impl;
+    }
+
+    const char* c_str() const
+    {
+        return str_impl.c_str();
+    }
+
+    char& operator[](std::size_t index)
+    {
+        return str_impl[index];
+    }
+
+    const char& operator[](std::size_t index) const
+    {
+        return str_impl[index];
+    }
+
+    char& back()
+    {
+        return str_impl.back();
+    }
+
+    const char& back() const
+    {
+        return str_impl.back();
+    }
+
+    void clear()
+    {
+        str_impl.clear();
+    }
+
+    const value_type* data() const
+    {
+        return str_impl.data();
+    }
+
+    bool empty() const
+    {
+        return str_impl.empty();
+    }
+
+    std::size_t find(const alt_string& str, std::size_t pos = 0) const
+    {
+        return str_impl.find(str.str_impl, pos);
+    }
+
+    // needed by binary_writer's BSON support, which probes string keys for
+    // embedded NUL characters via find(char)
+    std::size_t find(char c, std::size_t pos = 0) const
+    {
+        return str_impl.find(c, pos);
+    }
+
+    std::size_t find_first_of(char c, std::size_t pos = 0) const
+    {
+        return str_impl.find_first_of(c, pos);
+    }
+
+    alt_string substr(std::size_t pos = 0, std::size_t count = npos) const
+    {
+        const std::string s = str_impl.substr(pos, count);
+        return {s.data(), s.size()};
+    }
+
+    alt_string& replace(std::size_t pos, std::size_t count, const alt_string& str)
+    {
+        str_impl.replace(pos, count, str.str_impl);
+        return *this;
+    }
+
+    void reserve(std::size_t new_cap = 0)
+    {
+        str_impl.reserve(new_cap);
+    }
+
+  private:
+    std::string str_impl {}; // NOLINT(readability-redundant-member-init)
+
+    friend bool operator<(const char* /*op1*/, const alt_string& /*op2*/) noexcept;
+};
+
+void int_to_string(alt_string& target, std::size_t value)
+{
+    target = std::to_string(value).c_str();
+}
+
+using alt_json = nlohmann::basic_json <
+                 std::map,
+                 std::vector,
+                 alt_string,
+                 bool,
+                 std::int64_t,
+                 std::uint64_t,
+                 double,
+                 std::allocator,
+                 nlohmann::adl_serializer >;
+
+bool operator<(const char* op1, const alt_string& op2) noexcept
+{
+    return op1 < op2.str_impl;
+}
+
+namespace
+{
+
+// collects the object keys of j, in iteration order
+std::vector<std::string> collect_keys(const ordered_json& j)
+{
+    std::vector<std::string> result;
+    for (auto it = j.cbegin(); it != j.cend(); ++it)
+    {
+        result.push_back(it.key());
+    }
+    return result;
+}
+
+// a nested object/array value with keys inserted in non-alphabetical order,
+// used to check both round-trip equality and (for ordered_json) that
+// insertion order survives a trip through a binary format
+ordered_json make_rich_ordered_json()
+{
+    ordered_json j;
+    j["zebra"] = 1;
+    j["apple"] = ordered_json::array({1, 2, 3});
+    j["mango"]["z_nested"] = true;
+    j["mango"]["a_nested"] = nullptr;
+    j["banana"] = "some text";
+    j["cherry"] = 3.14;
+    return j;
+}
+
+alt_json make_rich_alt_json()
+{
+    alt_json j;
+    j["zebra"] = 1;
+    j["apple"] = alt_json::array({1, 2, 3});
+    j["mango"]["z_nested"] = true;
+    j["mango"]["a_nested"] = nullptr;
+    j["banana"] = "some text";
+    j["cherry"] = 3.14;
+    return j;
+}
+
+} // namespace
+
+TEST_CASE("ordered_json across binary formats")
+{
+    const ordered_json original = make_rich_ordered_json();
+    const std::vector<std::string> original_keys = collect_keys(original);
+    const std::vector<std::string> original_mango_keys = collect_keys(original["mango"]);
+
+    SECTION("CBOR")
+    {
+        const auto bytes = ordered_json::to_cbor(original);
+        const auto restored = ordered_json::from_cbor(bytes);
+        CHECK(restored == original);
+        CHECK(collect_keys(restored) == original_keys);
+        CHECK(collect_keys(restored["mango"]) == original_mango_keys);
+    }
+
+    SECTION("MessagePack")
+    {
+        const auto bytes = ordered_json::to_msgpack(original);
+        const auto restored = ordered_json::from_msgpack(bytes);
+        CHECK(restored == original);
+        CHECK(collect_keys(restored) == original_keys);
+        CHECK(collect_keys(restored["mango"]) == original_mango_keys);
+    }
+
+    SECTION("UBJSON")
+    {
+        const auto bytes = ordered_json::to_ubjson(original);
+        const auto restored = ordered_json::from_ubjson(bytes);
+        CHECK(restored == original);
+        CHECK(collect_keys(restored) == original_keys);
+        CHECK(collect_keys(restored["mango"]) == original_mango_keys);
+    }
+
+    SECTION("BSON")
+    {
+        const auto bytes = ordered_json::to_bson(original);
+        const auto restored = ordered_json::from_bson(bytes);
+        CHECK(restored == original);
+        CHECK(collect_keys(restored) == original_keys);
+        CHECK(collect_keys(restored["mango"]) == original_mango_keys);
+    }
+
+    SECTION("BJData")
+    {
+        const auto bytes = ordered_json::to_bjdata(original);
+        const auto restored = ordered_json::from_bjdata(bytes);
+        CHECK(restored == original);
+        CHECK(collect_keys(restored) == original_keys);
+        CHECK(collect_keys(restored["mango"]) == original_mango_keys);
+    }
+}
+
+TEST_CASE("alt_json (custom string_t) across binary formats")
+{
+    const alt_json original = make_rich_alt_json();
+
+    SECTION("CBOR")
+    {
+        const auto bytes = alt_json::to_cbor(original);
+        const auto restored = alt_json::from_cbor(bytes);
+        CHECK(restored == original);
+    }
+
+    SECTION("MessagePack")
+    {
+        const auto bytes = alt_json::to_msgpack(original);
+        const auto restored = alt_json::from_msgpack(bytes);
+        CHECK(restored == original);
+    }
+
+    SECTION("UBJSON")
+    {
+        const auto bytes = alt_json::to_ubjson(original);
+        const auto restored = alt_json::from_ubjson(bytes);
+        CHECK(restored == original);
+    }
+
+    SECTION("BSON")
+    {
+        const auto bytes = alt_json::to_bson(original);
+        const auto restored = alt_json::from_bson(bytes);
+        CHECK(restored == original);
+    }
+
+    SECTION("BJData")
+    {
+        const auto bytes = alt_json::to_bjdata(original);
+        const auto restored = alt_json::from_bjdata(bytes);
+        CHECK(restored == original);
+    }
+}
+
+TEST_CASE("ordered_json operator== is sensitive to key order")
+{
+    // Unlike nlohmann::json (whose object_t is a std::map, so equality never
+    // depends on insertion order), ordered_json's object_t (ordered_map) is a
+    // std::vector<std::pair<Key, T>> under the hood, and does not define its
+    // own operator==: it inherits std::vector's element-wise comparison. As a
+    // result, two ordered_json objects holding the very same key/value pairs
+    // in different insertion order compare *unequal*. This is the property
+    // that makes the round-trip `CHECK(restored == original)` checks above a
+    // meaningful order-preservation check by themselves (the explicit
+    // collect_keys() comparisons make that check explicit/readable, and
+    // guard against this operator== behavior ever changing).
+    ordered_json a;
+    a["x"] = 1;
+    a["y"] = 2;
+
+    ordered_json b;
+    b["y"] = 2;
+    b["x"] = 1;
+
+    CHECK(a.size() == b.size());
+    CHECK(a["x"] == b["x"]);
+    CHECK(a["y"] == b["y"]);
+    CHECK_FALSE(a == b);
+}
+
+TEST_CASE("duplicate keys in a binary-encoded object")
+{
+    // CBOR encoding of a map with two entries under the same key "a": {"a": 1, "a": 2}
+    const std::vector<std::uint8_t> cbor_bytes
+    {
+        0xA2, 0x61, 'a', 0x01, 0x61, 'a', 0x02
+    };
+
+    // Both json (std::map, via operator[]) and ordered_json (ordered_map, via
+    // operator[]) build binary-decoded objects by looking up/creating the
+    // entry for each incoming key and then assigning the value into it. This
+    // means a repeated key does *not* produce two entries in either case;
+    // instead, the *first* occurrence's position is kept (relevant only for
+    // ordered_json) while the *last* occurrence's value wins (for both) --
+    // this matches operator[]'s "assign the referenced slot" semantics, and
+    // is worth noting because it differs from the initializer-list
+    // construction path (`ordered_json{{"a",1},{"a",2}}`), which builds
+    // through insert()/emplace() and therefore keeps the *first* value, not
+    // the last (see the "There are no dup keys..." case in
+    // unit-ordered_json.cpp).
+    const auto j = json::from_cbor(cbor_bytes);
+    const auto oj = ordered_json::from_cbor(cbor_bytes);
+
+    CHECK(j.size() == 1);
+    CHECK(oj.size() == 1);
+    CHECK(j["a"] == 2);
+    CHECK(oj["a"] == 2);
+    CHECK(j == json(oj));
+}
+
+TEST_CASE("ordered_json through flatten/unflatten")
+{
+    const ordered_json original = make_rich_ordered_json();
+    const std::vector<std::string> original_keys = collect_keys(original);
+    const std::vector<std::string> original_mango_keys = collect_keys(original["mango"]);
+
+    const ordered_json flat = original.flatten();
+    const ordered_json unflattened = flat.unflatten();
+
+    CHECK(unflattened == original);
+    // flatten() walks the value depth-first in iteration order and
+    // unflatten() re-inserts each flattened key via operator[] in the flat
+    // object's iteration order, so for ordered_json the original key order
+    // (both top-level and nested) is preserved end-to-end.
+    CHECK(collect_keys(unflattened) == original_keys);
+    CHECK(collect_keys(unflattened["mango"]) == original_mango_keys);
+}
+
+TEST_CASE("ordered_json through diff/patch/patch_inplace")
+{
+    ordered_json original;
+    original["one"] = 1;
+    original["two"] = 2;
+    original["three"] = 3;
+
+    ordered_json target = original;
+    target["one"] = 100;      // replace
+    target.erase("two");      // remove
+    target["four"] = 4;       // add
+
+    const ordered_json patch = ordered_json::diff(original, target);
+
+    SECTION("patch")
+    {
+        const ordered_json patched = original.patch(patch);
+        CHECK(patched == target);
+    }
+
+    SECTION("patch_inplace")
+    {
+        ordered_json copy = original;
+        copy.patch_inplace(patch);
+        CHECK(copy == target);
+    }
+}
+
+TEST_CASE("ordered_json through merge_patch")
+{
+    ordered_json original;
+    original["a"] = 1;
+    original["b"] = 2;
+
+    const ordered_json patch = {{"b", nullptr}, {"c", 3}};
+
+    original.merge_patch(patch);
+
+    ordered_json expected;
+    expected["a"] = 1;
+    expected["c"] = 3;
+
+    CHECK(original == expected);
+    CHECK(collect_keys(original) == collect_keys(expected));
+}

tests/src/unit-std-format.cpp

@@ -17,6 +17,7 @@
 
 #include <nlohmann/json.hpp>
 using json = nlohmann::json;
+using ordered_json = nlohmann::ordered_json;
 
 // JSON_HAS_CPP_20 (do not remove; see note at top of file)
 #if JSON_HAS_STD_FORMAT
@@ -93,4 +94,16 @@ TEST_CASE("std::formatter<nlohmann::json>")
     }
 }
 
+TEST_CASE("std::formatter<nlohmann::ordered_json>")
+{
+    // spot-check a non-default basic_json instantiation, since the formatter
+    // is written against the generic NLOHMANN_BASIC_JSON_TPL_DECLARATION
+    // template and must actually instantiate (and behave correctly) for
+    // template arguments other than nlohmann::json
+    const ordered_json j = {{"foo", 1}, {"bar", {1, 2, 3}}};
+    CHECK(std::format("{}", j) == j.dump());
+    CHECK(std::format("{:#}", j) == j.dump(4));
+    CHECK(std::format("{:2}", j) == j.dump(2));
+}
+
 #endif