Throw out_of_range.411 for JSON Patch add into a null parent (#5917)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MKJf48vnGtTE25KscmjfaW
Signed-off-by: Niels Lohmann <niels.lohmann@gmail.com>

docs/mkdocs/docs/api/basic_json/patch.md

@@ -108,6 +108,7 @@ is thrown. In any case, the original value is not changed: the patch is applied
 - Added in version 2.0.0.
 - Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
   target location has a non-object/non-array parent in version 3.13.0.
+  This includes a `null` parent, which was previously silently converted to an object, in version 3.13.0.
 - Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
   location has a non-object/non-array parent in version 3.13.0.
 - Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper

docs/mkdocs/docs/api/basic_json/patch_inplace.md

@@ -106,6 +106,7 @@ function throws an exception.
 - Added in version 3.11.0.
 - Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
   target location has a non-object/non-array parent in version 3.13.0.
+  This includes a `null` parent, which was previously silently converted to an object, in version 3.13.0.
 - Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
   location has a non-object/non-array parent in version 3.13.0.
 - Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper

docs/mkdocs/docs/home/exceptions.md

@@ -1100,6 +1100,8 @@ A JSON Patch `add` operation cannot be applied because the target location's par
 
     This exception was added in version 3.13.0. Before that, this situation hit an internal assertion (aborting the program in debug builds) or was silently ignored when assertions were disabled.
 
+    A `null` parent is rejected as well. Before version 3.13.0, an `add` into a `null` parent silently converted it to an object (e.g., `add` at `/foo/bar` turned `{"foo":null}` into `{"foo":{"bar":1}}`).
+
 ### json.exception.out_of_range.412
 
 BSON stores the length of documents, arrays, strings, and binary values in a signed 32-bit integer, and MessagePack

include/nlohmann/json.hpp

@@ -7003,7 +7003,6 @@ public:
 
             switch (parent.m_data.m_type)
             {
-                case value_t::null:
                 case value_t::object:
                 {
                     // use operator[] to add value
@@ -7035,6 +7034,7 @@ public:
 
                 // the parent of an "add" target must be an object or array
                 // (see #4292)
+                case value_t::null:
                 case value_t::string:
                 case value_t::boolean:
                 case value_t::number_integer:

single_include/nlohmann/json.hpp

@@ -42793,7 +42793,6 @@ public:
 
             switch (parent.m_data.m_type)
             {
-                case value_t::null:
                 case value_t::object:
                 {
                     // use operator[] to add value
@@ -42825,6 +42824,7 @@ public:
 
                 // the parent of an "add" target must be an object or array
                 // (see #4292)
+                case value_t::null:
                 case value_t::string:
                 case value_t::boolean:
                 case value_t::number_integer:

tests/src/unit-json_patch.cpp

@@ -1515,6 +1515,24 @@ TEST_CASE("JSON patch - add to a primitive parent (regression #4292)")
 #endif
     }
 
+    SECTION("null parent")
+    {
+        json const doc = {{"foo", nullptr}};
+        json const patch = {{{"op", "add"}, {"path", "/foo/bar"}, {"value", 1}}};
+#if JSON_DIAGNOSTICS
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.411] (/foo) cannot add value: the JSON Patch 'add' target's parent is of type null, but must be an object or array", json::out_of_range&);
+#else
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.411] cannot add value: the JSON Patch 'add' target's parent is of type null, but must be an object or array", json::out_of_range&);
+#endif
+    }
+
+    SECTION("null document")
+    {
+        json const doc = nullptr;
+        json const patch = {{{"op", "add"}, {"path", "/-"}, {"value", 1}}};
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.411] cannot add value: the JSON Patch 'add' target's parent is of type null, but must be an object or array", json::out_of_range&);
+    }
+
     SECTION("number parent")
     {
         json const doc = {{"foo", 1}};