Add deprecated from_bon8/from_bjdata(ptr, len) overloads

from_bon8(ptr, len) and from_bjdata(ptr, len) had no overload for a
pointer and a length, unlike from_cbor/from_msgpack/from_ubjson/
from_bson. The call instead bound to from_*(InputType&&, bool strict),
which read ptr as a NUL-terminated C string via strlen and silently
converted len to the strict flag. Data containing a 0x00 byte was cut
off there; data without one was read past the end of the buffer.

Add a deprecated (ptr, len, strict, allow_exceptions) overload for
each function that forwards to (ptr, ptr + len, ...), matching the
existing deprecated overloads of the other four binary readers. Since
neither function ever had this overload, the deprecation is declared
as of version 3.13.0, the next unreleased version, rather than the
version each function was originally added in.

Fixes #5648.

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

docs/mkdocs/docs/api/basic_json/from_bjdata.md

@@ -111,3 +111,12 @@ Linear in the size of the input.
 - Added in version 3.11.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
+
+!!! warning "Deprecation"
+
+    - Overload (2) replaces calls to `from_bjdata` with a pointer and a length as first two parameters, which has been
+      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      `#!cpp from_bjdata(ptr, len, ...);` with `#!cpp from_bjdata(ptr, ptr+len, ...);`.
+
+    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
+    function.

docs/mkdocs/docs/api/basic_json/from_bon8.md

@@ -106,3 +106,12 @@ Linear in the size of the input.
 ## Version history
 
 - Added in version 3.13.0.
+
+!!! warning "Deprecation"
+
+    - Overload (2) replaces calls to `from_bon8` with a pointer and a length as first two parameters, which has been
+      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      `#!cpp from_bon8(ptr, len, ...);` with `#!cpp from_bon8(ptr, ptr+len, ...);`.
+
+    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
+    function.

docs/mkdocs/docs/api/macros/json_brace_init_copy_semantics.md

@@ -50,11 +50,9 @@ The default value is `0` (disabled — existing behavior is preserved).
     ```
 
     Code that relies on these producing arrays must use `json::array()` instead (see below). Lists with more than one
-    element, and a single `[string, value]` pair *written as a braced list*, such as `{{"key", "value"}}`, which still
-    creates an object, are not affected. This exception is based on how the pair is written, not on the shape of its
-    value: an existing JSON value that happens to be a two-element array with a string as its first element, such as
-    `json arr = {"key", 42};`, is still copied by `json j{arr};` rather than turned into an object. The library's own
-    conversions are not affected either: for example, `std::tuple<int>{5}` still becomes `[5]`.
+    element, and a single `[string, value]` pair such as `{{"key", "value"}}`, which still creates an object, are not
+    affected. The library's own conversions are not affected either: for example, `std::tuple<int>{5}` still becomes
+    `[5]`.
 
 !!! note "ABI compatibility"
 

include/nlohmann/detail/json_ref.hpp

@@ -34,7 +34,6 @@ class json_ref
 
     json_ref(std::initializer_list<json_ref> init)
         : owned_value(init)
-        , braced_list(true)
     {}
 
     template <
@@ -70,17 +69,9 @@ class json_ref
         return &** this;
     }
 
-    /// whether the value was written as a braced list, such as {"key", 1},
-    /// rather than given as a value
-    bool is_braced_list() const noexcept
-    {
-        return braced_list;
-    }
-
   private:
     mutable value_type owned_value = nullptr;
     value_type const* value_ref = nullptr;
-    bool braced_list = false;
 };
 
 }  // namespace detail

include/nlohmann/json.hpp

@@ -1672,18 +1672,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                bool type_deduction = true,
                value_t manual_type = value_t::array)
     {
-#if JSON_BRACE_INIT_COPY_SEMANTICS
-        // a single element that is a value rather than a braced list is
-        // copied or moved as is, whatever its content looks like
-        if (type_deduction && init.size() == 1 && !init.begin()->is_braced_list())
-        {
-            *this = init.begin()->moved_or_copied();
-            set_parents();
-            assert_invariant();
-            return;
-        }
-#endif
-
         // check if each element is an array with two elements whose first
         // element is a string
         bool is_an_object = std::all_of(init.begin(), init.end(),
@@ -5559,6 +5547,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return result;
     }
 
+    template<typename T>
+    JSON_HEDLEY_WARN_UNUSED_RESULT
+    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bjdata(ptr, ptr + len))
+    static basic_json from_bjdata(const T* ptr, std::size_t len,
+                                  const bool strict = true,
+                                  const bool allow_exceptions = true)
+    {
+        return from_bjdata(ptr, ptr + len, strict, allow_exceptions);
+    }
+
     /// @brief create a JSON value from an input in BON8 format
     /// @sa https://json.nlohmann.me/api/basic_json/from_bon8/
     template<typename InputType>
@@ -5596,6 +5594,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return result;
     }
 
+    template<typename T>
+    JSON_HEDLEY_WARN_UNUSED_RESULT
+    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bon8(ptr, ptr + len))
+    static basic_json from_bon8(const T* ptr, std::size_t len,
+                                const bool strict = true,
+                                const bool allow_exceptions = true)
+    {
+        return from_bon8(ptr, ptr + len, strict, allow_exceptions);
+    }
+
     /// @brief create a JSON value from an input in BSON format
     /// @sa https://json.nlohmann.me/api/basic_json/from_bson/
     template<typename InputType>

single_include/nlohmann/json.hpp

@@ -20047,7 +20047,6 @@ class json_ref
 
     json_ref(std::initializer_list<json_ref> init)
         : owned_value(init)
-        , braced_list(true)
     {}
 
     template <
@@ -20083,17 +20082,9 @@ class json_ref
         return &** this;
     }
 
-    /// whether the value was written as a braced list, such as {"key", 1},
-    /// rather than given as a value
-    bool is_braced_list() const noexcept
-    {
-        return braced_list;
-    }
-
   private:
     mutable value_type owned_value = nullptr;
     value_type const* value_ref = nullptr;
-    bool braced_list = false;
 };
 
 }  // namespace detail
@@ -27762,18 +27753,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                bool type_deduction = true,
                value_t manual_type = value_t::array)
     {
-#if JSON_BRACE_INIT_COPY_SEMANTICS
-        // a single element that is a value rather than a braced list is
-        // copied or moved as is, whatever its content looks like
-        if (type_deduction && init.size() == 1 && !init.begin()->is_braced_list())
-        {
-            *this = init.begin()->moved_or_copied();
-            set_parents();
-            assert_invariant();
-            return;
-        }
-#endif
-
         // check if each element is an array with two elements whose first
         // element is a string
         bool is_an_object = std::all_of(init.begin(), init.end(),
@@ -31649,6 +31628,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return result;
     }
 
+    template<typename T>
+    JSON_HEDLEY_WARN_UNUSED_RESULT
+    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bjdata(ptr, ptr + len))
+    static basic_json from_bjdata(const T* ptr, std::size_t len,
+                                  const bool strict = true,
+                                  const bool allow_exceptions = true)
+    {
+        return from_bjdata(ptr, ptr + len, strict, allow_exceptions);
+    }
+
     /// @brief create a JSON value from an input in BON8 format
     /// @sa https://json.nlohmann.me/api/basic_json/from_bon8/
     template<typename InputType>
@@ -31686,6 +31675,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return result;
     }
 
+    template<typename T>
+    JSON_HEDLEY_WARN_UNUSED_RESULT
+    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bon8(ptr, ptr + len))
+    static basic_json from_bon8(const T* ptr, std::size_t len,
+                                const bool strict = true,
+                                const bool allow_exceptions = true)
+    {
+        return from_bon8(ptr, ptr + len, strict, allow_exceptions);
+    }
+
     /// @brief create a JSON value from an input in BSON format
     /// @sa https://json.nlohmann.me/api/basic_json/from_bson/
     template<typename InputType>

tests/src/unit-bjdata.cpp

@@ -4572,3 +4572,31 @@ TEST_CASE("BJData roundtrips" * doctest::skip())
         }
     }
 }
+
+TEST_CASE("issue #5648 - from_bjdata(ptr, len) must read len bytes, not treat ptr as a C string")
+{
+    // to_bjdata() encodes the integer 0 as the two bytes 'i' 0x00 (a BJData
+    // type marker followed by the value byte 0x00), so the packed data
+    // below contains a 0x00 byte before its end.
+    const json j = {{"a", 0}};
+    const std::vector<std::uint8_t> packed = json::to_bjdata(j);
+    bool contains_nul = false;
+    for (const auto byte : packed)
+    {
+        contains_nul |= (byte == 0x00);
+    }
+    REQUIRE(contains_nul);
+
+    // before the fix, from_bjdata had no (ptr, len) overload, so this call
+    // bound to from_bjdata(InputType&&, bool strict) instead: ptr was read
+    // as a NUL-terminated C string (stopping at the embedded 0x00 byte), and
+    // len was silently converted to the strict flag. The deprecated
+    // overload added for this issue forwards to from_bjdata(ptr, ptr + len,
+    // ...) instead, like from_ubjson's deprecated (ptr, len) overload does.
+    json result;
+    CHECK_NOTHROW(result = json::from_bjdata(packed.data(), packed.size()));
+    CHECK(result == j);
+
+    // len must not collapse into the strict flag either
+    CHECK(json::from_bjdata(packed.data(), packed.size(), false) == j);
+}

tests/src/unit-bon8.cpp

@@ -1010,6 +1010,34 @@ TEST_CASE("BON8 roundtrips" * doctest::skip())
     }
 }
 
+TEST_CASE("issue #5648 - from_bon8(ptr, len) must read len bytes, not treat ptr as a C string")
+{
+    // to_bon8() encodes the integer 40 as the two bytes 0xC2 0x00 (a BON8
+    // lead byte followed by a continuation byte of 0x00), so the packed data
+    // below contains a 0x00 byte before its end.
+    const json j = {{"a", 40}, {"b", "x"}};
+    const std::vector<std::uint8_t> packed = json::to_bon8(j);
+    bool contains_nul = false;
+    for (const auto byte : packed)
+    {
+        contains_nul |= (byte == 0x00);
+    }
+    REQUIRE(contains_nul);
+
+    // before the fix, from_bon8 had no (ptr, len) overload, so this call
+    // bound to from_bon8(InputType&&, bool strict) instead: ptr was read as
+    // a NUL-terminated C string (stopping at the embedded 0x00 byte), and
+    // len was silently converted to the strict flag. The deprecated
+    // overload added for this issue forwards to from_bon8(ptr, ptr + len,
+    // ...) instead, like from_cbor's deprecated (ptr, len) overload does.
+    json result;
+    CHECK_NOTHROW(result = json::from_bon8(packed.data(), packed.size()));
+    CHECK(result == j);
+
+    // len must not collapse into the strict flag either
+    CHECK(json::from_bon8(packed.data(), packed.size(), false) == j);
+}
+
 #ifdef JSON_HAS_CPP_17
 TEST_CASE("BON8 with std::byte")
 {

tests/src/unit-brace-init-copy-semantics.cpp

@@ -72,28 +72,6 @@ TEST_CASE("JSON_BRACE_INIT_COPY_SEMANTICS")
         CHECK(j7 == json::array({1, 2}));
     }
 
-    SECTION("single-element brace initialization copies a pair-shaped array value (#5662)")
-    {
-        // a JSON value that happens to be a 2-element array whose first
-        // element is a string must still be copied, not turned into an
-        // object; only a braced list written in the source, such as the
-        // inner {"key", "value"} of {{"key", "value"}}, describes an object
-        json const pair_shaped = json::array({"key", 42});
-
-        json const j1{pair_shaped};
-        CHECK(j1.is_array());
-        CHECK(j1 == pair_shaped);
-
-        json const j2 = {pair_shaped};
-        CHECK(j2.is_array());
-        CHECK(j2 == pair_shaped);
-
-        // the same holds for an rvalue of the same shape
-        json const j3{json::array({"key", 42})};
-        CHECK(j3.is_array());
-        CHECK(j3 == pair_shaped);
-    }
-
     SECTION("what the macro does not change")
     {
         // lists with more than one element are unaffected