Bump the codeql-action group with 4 updates

Bumps the codeql-action group with 4 updates: [github/codeql-action/init](https://github.com/github/codeql-action), [github/codeql-action/autobuild](https://github.com/github/codeql-action), [github/codeql-action/analyze](https://github.com/github/codeql-action) and [github/codeql-action/upload-sarif](https://github.com/github/codeql-action).


Updates `github/codeql-action/init` from 4.37.7 to 4.37.8
- [Release notes](https://github.com/github/codeql-action/releases)
- [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md)
- [Commits](https://github.com/github/codeql-action/compare/ff2f1c621b7f889edc0d3c761ac2e6a3f8cdb0dd...db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28)

Updates `github/codeql-action/autobuild` from 4.37.7 to 4.37.8
- [Release notes](https://github.com/github/codeql-action/releases)
- [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md)
- [Commits](https://github.com/github/codeql-action/compare/ff2f1c621b7f889edc0d3c761ac2e6a3f8cdb0dd...db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28)

Updates `github/codeql-action/analyze` from 4.37.7 to 4.37.8
- [Release notes](https://github.com/github/codeql-action/releases)
- [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md)
- [Commits](https://github.com/github/codeql-action/compare/ff2f1c621b7f889edc0d3c761ac2e6a3f8cdb0dd...db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28)

Updates `github/codeql-action/upload-sarif` from 4.37.7 to 4.37.8
- [Release notes](https://github.com/github/codeql-action/releases)
- [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md)
- [Commits](https://github.com/github/codeql-action/compare/ff2f1c621b7f889edc0d3c761ac2e6a3f8cdb0dd...db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28)

---
updated-dependencies:
- dependency-name: github/codeql-action/init
  dependency-version: 4.37.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: codeql-action
- dependency-name: github/codeql-action/autobuild
  dependency-version: 4.37.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: codeql-action
- dependency-name: github/codeql-action/analyze
  dependency-version: 4.37.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: codeql-action
- dependency-name: github/codeql-action/upload-sarif
  dependency-version: 4.37.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: codeql-action
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/check_amalgamation.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+      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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+      uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
       with:
         egress-policy: audit
 
@@ -38,14 +38,14 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+      uses: github/codeql-action/init@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8
       with:
         languages: c-cpp
 
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+      uses: github/codeql-action/autobuild@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+      uses: github/codeql-action/analyze@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8

.github/workflows/comment_check_amalgamation.yml

@@ -19,7 +19,7 @@ jobs:
       pull-requests: write
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -43,6 +43,6 @@ jobs:
           output: 'flawfinder_results.sarif'
 
       - name: Upload analysis results to GitHub Security tab
-        uses: github/codeql-action/upload-sarif@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+        uses: github/codeql-action/upload-sarif@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8
         with:
           sarif_file: ${{github.workspace}}/flawfinder_results.sarif

.github/workflows/labeler.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -76,6 +76,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+        uses: github/codeql-action/upload-sarif@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8
         with:
           sarif_file: results.sarif

.github/workflows/semgrep.yml

@@ -32,7 +32,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 
@@ -61,7 +61,7 @@ jobs:
 
       # Upload SARIF file generated in previous step
       - name: Upload SARIF file
-        uses: github/codeql-action/upload-sarif@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+        uses: github/codeql-action/upload-sarif@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8
         with:
           sarif_file: semgrep.sarif
         if: always()

.github/workflows/stale.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        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@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
+        uses: step-security/harden-runner@05e31511f85b41b11d1cf0ef85d0992719546e2c # v2.21.0
         with:
           egress-policy: audit
 

docs/mkdocs/docs/api/basic_json/to_bjdata.md

@@ -52,6 +52,11 @@ optional, `#!cpp bjdata_version_t::draft2` by default.
 
 Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
 
+## Exceptions
+
+- Throws [`other_error.502`](../../home/exceptions.md#jsonexceptionother_error502) if `use_type` is true and `use_size`
+  is false.
+
 ## Complexity
 
 Linear in the size of the JSON value `j`.

docs/mkdocs/docs/api/basic_json/to_bson.md

@@ -46,7 +46,9 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 ## Complexity
 
-Linear in the size of the JSON value `j`.
+Proportional to the size of the JSON value `j` multiplied by its maximum nesting
+depth, `O(n × d)`. BSON length prefixes are computed recursively before nested
+values are written.
 
 ## Examples
 

docs/mkdocs/docs/api/basic_json/to_ubjson.md

@@ -45,6 +45,11 @@ The exact mapping and its limitations are described on a [dedicated page](../../
 
 Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
 
+## Exceptions
+
+- Throws [`other_error.502`](../../home/exceptions.md#jsonexceptionother_error502) if `use_type` is true and `use_size`
+  is false.
+
 ## Complexity
 
 Linear in the size of the JSON value `j`.

docs/mkdocs/docs/features/binary_formats/bson.md

@@ -98,6 +98,17 @@ The library maps BSON record types to JSON value types as follows:
     This library deserializes BSON type `0x11` (Timestamp) as a `number_unsigned` value. The 64-bit value is preserved,
     but the Timestamp type information is not.
 
+!!! warning "Lenient BSON input handling"
+
+    The BSON reader is lenient in a few areas where the BSON specification is more restrictive:
+
+    - array element keys are not checked against the required decimal sequence (`0`, `1`, `2`, ...),
+    - any non-zero byte is accepted as `true` for the boolean type, and
+    - the payload for binary subtype `0x02` is returned as-is, including its inner length prefix.
+
+    If BSON input must be validated for strict specification compliance, validate it separately before passing it to
+    `from_bson()`.
+
 ??? example
 
     ```cpp

docs/mkdocs/docs/features/conversions.md

@@ -54,6 +54,30 @@ json j = {1.0, "hello", 42};
 auto t = j.get<std::tuple<double, std::string, int>>();  // {1.0, "hello", 42}
 ```
 
+!!! warning "Serializing a `std::pair`/`std::tuple` whose every element is a string-keyed pair"
+
+    When *every* element of a `#!cpp std::pair` or `#!cpp std::tuple` is itself a two-element array whose first
+    element is a string (for example `#!cpp std::pair<std::string, int>`), serializing it produces a JSON **object**
+    instead of the expected array:
+
+    ```cpp
+    using kv = std::pair<std::string, int>;
+    json j = std::pair<kv, kv>{{"a", 1}, {"b", 2}};  // {"a":1,"b":2}, not [["a",1],["b",2]]
+    ```
+
+    This is a consequence of the [brace-initializer object-detection rule](creating_values.md): the same rule that
+    lets `#!cpp json{{"a", 1}, {"b", 2}}` create an object also fires here. The resulting object cannot be read back
+    into the original type (`#!cpp get<std::pair<kv, kv>>()` throws [`type_error.302`](../home/exceptions.md#jsonexceptiontype_error302)),
+    and duplicate keys collapse into one, losing elements. This only affects `#!cpp std::pair`/`#!cpp std::tuple`
+    themselves; a `#!cpp std::vector<std::pair<std::string, int>>`, or a pair/tuple with at least one element that is
+    not a string-keyed pair, serializes to an array as expected. To force an array, build one explicitly from the
+    elements with [`array`](../api/basic_json/array.md):
+
+    ```cpp
+    std::pair<kv, kv> p{{"a", 1}, {"b", 2}};
+    json a = json::array({p.first, p.second});  // [["a",1],["b",2]]
+    ```
+
 !!! info "Extracting references into a tuple"
 
     A tuple type may also hold references (e.g. `#!cpp std::tuple<double&, std::string&>`) to avoid copying: `get`

docs/mkdocs/docs/home/exceptions.md

@@ -965,3 +965,19 @@ A JSON Patch operation 'test' failed. The unsuccessful operation is also printed
     ```
     [json.exception.other_error.501] unsuccessful: {"op":"test","path":"/baz","value":"bar"}
     ```
+
+### json.exception.other_error.502
+
+[`to_ubjson`](../api/basic_json/to_ubjson.md) and [`to_bjdata`](../api/basic_json/to_bjdata.md) were called with
+`use_type = true` but `use_size = false`. UBJSON requires a size marker (`#`) after a type marker (`$`).
+
+!!! failure "Example message"
+
+    ```
+    [json.exception.other_error.502] use_type requires use_size = true
+    ```
+
+!!! note
+
+    This exception was added in version 3.13.0. Before that, debug builds aborted on an assertion and release builds
+    wrote a `$` marker without `#`, which [`from_ubjson`](../api/basic_json/from_ubjson.md) then rejected.

include/nlohmann/detail/output/binary_writer.hpp

@@ -813,7 +813,10 @@ class binary_writer
                 bool prefix_required = true;
                 if (use_type && !j.m_data.m_value.array->empty())
                 {
-                    JSON_ASSERT(use_count);
+                    if (!use_count)
+                    {
+                        JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
+                    }
                     const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
                     const bool same_prefix = std::all_of(j.begin() + 1, j.end(),
                                                          [this, first_prefix, use_bjdata](const BasicJsonType & v)
@@ -859,7 +862,10 @@ class binary_writer
 
                 if (use_type && (bjdata_draft3 || !j.m_data.m_value.binary->empty()))
                 {
-                    JSON_ASSERT(use_count);
+                    if (!use_count)
+                    {
+                        JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
+                    }
                     oa->write_character(to_char_type('$'));
                     oa->write_character(bjdata_draft3 ? 'B' : 'U');
                 }
@@ -911,7 +917,10 @@ class binary_writer
                 bool prefix_required = true;
                 if (use_type && !j.m_data.m_value.object->empty())
                 {
-                    JSON_ASSERT(use_count);
+                    if (!use_count)
+                    {
+                        JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
+                    }
                     const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
                     const bool same_prefix = std::all_of(j.begin(), j.end(),
                                                          [this, first_prefix, use_bjdata](const BasicJsonType & v)

include/nlohmann/json.hpp

@@ -3516,7 +3516,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             if (merge_objects && it.value().is_object())
             {
                 auto it2 = m_data.m_value.object->find(it.key());
-                if (it2 != m_data.m_value.object->end())
+                // Only recurse when the existing value is itself an object.
+                // Otherwise overwrite, matching the documented "all other values
+                // are overwritten as usual" behavior (see #5402).
+                if (it2 != m_data.m_value.object->end() && it2->second.is_object())
                 {
                     it2->second.update(it.value(), true);
 #if JSON_DIAGNOSTICS

single_include/nlohmann/json.hpp

@@ -17756,7 +17756,10 @@ class binary_writer
                 bool prefix_required = true;
                 if (use_type && !j.m_data.m_value.array->empty())
                 {
-                    JSON_ASSERT(use_count);
+                    if (!use_count)
+                    {
+                        JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
+                    }
                     const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
                     const bool same_prefix = std::all_of(j.begin() + 1, j.end(),
                                                          [this, first_prefix, use_bjdata](const BasicJsonType & v)
@@ -17802,7 +17805,10 @@ class binary_writer
 
                 if (use_type && (bjdata_draft3 || !j.m_data.m_value.binary->empty()))
                 {
-                    JSON_ASSERT(use_count);
+                    if (!use_count)
+                    {
+                        JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
+                    }
                     oa->write_character(to_char_type('$'));
                     oa->write_character(bjdata_draft3 ? 'B' : 'U');
                 }
@@ -17854,7 +17860,10 @@ class binary_writer
                 bool prefix_required = true;
                 if (use_type && !j.m_data.m_value.object->empty())
                 {
-                    JSON_ASSERT(use_count);
+                    if (!use_count)
+                    {
+                        JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
+                    }
                     const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
                     const bool same_prefix = std::all_of(j.begin(), j.end(),
                                                          [this, first_prefix, use_bjdata](const BasicJsonType & v)
@@ -24861,7 +24870,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             if (merge_objects && it.value().is_object())
             {
                 auto it2 = m_data.m_value.object->find(it.key());
-                if (it2 != m_data.m_value.object->end())
+                // Only recurse when the existing value is itself an object.
+                // Otherwise overwrite, matching the documented "all other values
+                // are overwritten as usual" behavior (see #5402).
+                if (it2 != m_data.m_value.object->end() && it2->second.is_object())
                 {
                     it2->second.update(it.value(), true);
 #if JSON_DIAGNOSTICS

tests/src/unit-bjdata.cpp

@@ -3843,6 +3843,48 @@ TEST_CASE("all BJData first bytes")
 }
 #endif
 
+TEST_CASE("BJData use_type requires use_size")
+{
+    SECTION("non-empty object throws other_error.502")
+    {
+        const json j = {{"a", 1}, {"b", 2}};
+        CHECK_THROWS_WITH_AS(json::to_bjdata(j, false, true),
+                             "[json.exception.other_error.502] use_type requires use_size = true",
+                             json::other_error&);
+    }
+
+    SECTION("non-empty array throws other_error.502")
+    {
+        const json j = {1, 2, 3};
+        CHECK_THROWS_WITH_AS(json::to_bjdata(j, false, true),
+                             "[json.exception.other_error.502] use_type requires use_size = true",
+                             json::other_error&);
+    }
+
+    SECTION("scalars do not throw with use_type=true, use_count=false")
+    {
+        CHECK_NOTHROW(json::to_bjdata(42, false, true));
+        CHECK_NOTHROW(json::to_bjdata(3.14, false, true));
+        CHECK_NOTHROW(json::to_bjdata("hello", false, true));
+        CHECK_NOTHROW(json::to_bjdata(true, false, true));
+        CHECK_NOTHROW(json::to_bjdata(nullptr, false, true));
+    }
+
+    SECTION("empty containers do not throw with use_type=true, use_count=false")
+    {
+        CHECK_NOTHROW(json::to_bjdata(json::array(), false, true));
+        CHECK_NOTHROW(json::to_bjdata(json::object(), false, true));
+    }
+
+    SECTION("valid combinations on non-empty containers")
+    {
+        const json j = {{"a", 1}, {"b", 2}};
+        CHECK_NOTHROW(json::to_bjdata(j, false, false));
+        CHECK_NOTHROW(json::to_bjdata(j, true, false));
+        CHECK_NOTHROW(json::to_bjdata(j, true, true));
+    }
+}
+
 TEST_CASE("BJData roundtrips" * doctest::skip())
 {
     SECTION("input from self-generated BJData files")

tests/src/unit-modifiers.cpp

@@ -801,6 +801,30 @@ TEST_CASE("modifiers")
                     j1.update(j2, true);
                     CHECK(j1 == json({{"string", "t"}, {"numbers", 1}}));
                 }
+
+                SECTION("overwrite primitive with object")
+                {
+                    json j1 = {{"k", 1}};
+                    json const j2 = {{"k", {{"x", 2}}}};
+                    j1.update(j2, true);
+                    CHECK(j1 == json({{"k", {{"x", 2}}}}));
+                }
+
+                SECTION("overwrite array with object")
+                {
+                    json j1 = {{"k", {1, 2}}};
+                    json const j2 = {{"k", {{"x", 2}}}};
+                    j1.update(j2, true);
+                    CHECK(j1 == json({{"k", {{"x", 2}}}}));
+                }
+
+                SECTION("overwrite nested primitive with object")
+                {
+                    json j1 = {{"k", {{"inner", 1}}}};
+                    json const j2 = {{"k", {{"inner", {{"x", 2}}}}}};
+                    j1.update(j2, true);
+                    CHECK(j1 == json({{"k", {{"inner", {{"x", 2}}}}}}));
+                }
             }
         }
     }

tests/src/unit-regression2.cpp

@@ -1555,4 +1555,15 @@ TEST_CASE("issue #5338 - truncated CBOR tagged binary subtype is rejected")
     }
 }
 
+TEST_CASE("issue #5402 - update(merge_objects=true) overwrites a primitive with an object")
+{
+    json t = {{"k", 1}};
+    t.update(json{{"k", {{"x", 2}}}}, true);
+    CHECK(t == json({{"k", {{"x", 2}}}}));
+
+    json mixed = {{"keep", {{"a", 1}}}, {"replace", 1}};
+    mixed.update(json{{"keep", {{"b", 2}}}, {"replace", {{"x", 2}}}}, true);
+    CHECK(mixed == json({{"keep", {{"a", 1}, {"b", 2}}}, {"replace", {{"x", 2}}}}));
+}
+
 DOCTEST_CLANG_SUPPRESS_WARNING_POP

tests/src/unit-ubjson.cpp

@@ -2503,6 +2503,48 @@ TEST_CASE("all UBJSON first bytes")
 }
 #endif
 
+TEST_CASE("UBJSON use_type requires use_size")
+{
+    SECTION("non-empty array throws other_error.502")
+    {
+        const json j = {1, 2, 3};
+        CHECK_THROWS_WITH_AS(json::to_ubjson(j, false, true),
+                             "[json.exception.other_error.502] use_type requires use_size = true",
+                             json::other_error&);
+    }
+
+    SECTION("non-empty object throws other_error.502")
+    {
+        const json j = {{"a", 1}, {"b", 2}};
+        CHECK_THROWS_WITH_AS(json::to_ubjson(j, false, true),
+                             "[json.exception.other_error.502] use_type requires use_size = true",
+                             json::other_error&);
+    }
+
+    SECTION("scalars do not throw with use_type=true, use_count=false")
+    {
+        CHECK_NOTHROW(json::to_ubjson(42, false, true));
+        CHECK_NOTHROW(json::to_ubjson(3.14, false, true));
+        CHECK_NOTHROW(json::to_ubjson("hello", false, true));
+        CHECK_NOTHROW(json::to_ubjson(true, false, true));
+        CHECK_NOTHROW(json::to_ubjson(nullptr, false, true));
+    }
+
+    SECTION("empty containers do not throw with use_type=true, use_count=false")
+    {
+        CHECK_NOTHROW(json::to_ubjson(json::array(), false, true));
+        CHECK_NOTHROW(json::to_ubjson(json::object(), false, true));
+    }
+
+    SECTION("valid combinations on non-empty containers")
+    {
+        const json j = {1, 2, 3};
+        CHECK_NOTHROW(json::to_ubjson(j, false, false));
+        CHECK_NOTHROW(json::to_ubjson(j, true, false));
+        CHECK_NOTHROW(json::to_ubjson(j, true, true));
+    }
+}
+
 TEST_CASE("UBJSON roundtrips" * doctest::skip())
 {
     SECTION("input from self-generated UBJSON files")