Throw when JSON Patch remove's target path resolves through a primitive or null parent

RFC 6902 (section 4.2) requires the target location of a "remove"
operation to exist. operation_remove handled parent.is_object() and
parent.is_array(), but had no final else branch: when the resolved
parent was a primitive value or null, neither branch matched and the
operation silently did nothing instead of failing.

Add the missing else branch, throwing out_of_range.413 with wording
that matches the existing out_of_range.411 thrown by the analogous
"add" case (operation_add) for the same kind of invalid parent.

Fixes #5396.

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

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

@@ -34,6 +34,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   ("add", "remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
   location has a parent that is neither an object nor an array.
+- Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
+  location has a parent that is neither an object nor an array.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -75,3 +77,5 @@ 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.
+- 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.

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

@@ -30,6 +30,8 @@ No guarantees, value may be corrupted by an unsuccessful patch operation.
   ("add", "remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
   location has a parent that is neither an object nor an array.
+- Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
+  location has a parent that is neither an object nor an array.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -72,3 +74,5 @@ 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.
+- 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.

docs/mkdocs/docs/home/exceptions.md

@@ -933,6 +933,20 @@ BSON stores the length of documents, arrays, strings, and binary values in a sig
     [`to_bson`](../api/basic_json/to_bson.md) produced documents with negative length prefixes that
     [`from_bson`](../api/basic_json/from_bson.md) rejected.
 
+### json.exception.out_of_range.413
+
+A JSON Patch `remove` operation cannot be applied because the target location's parent is neither an object nor an array. Per [RFC 6902](https://datatracker.ietf.org/doc/html/rfc6902), a `remove` target must reference a member of an existing object or an element of an existing array; a primitive value (string, number, boolean, etc.) or `null` has no members or elements to remove.
+
+!!! failure "Example message"
+
+    ```
+    cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array
+    ```
+
+!!! note
+
+    This exception was added in version 3.13.0. Before that, this situation was silently ignored (the `remove` operation had no effect).
+
 ## Further exceptions
 
 This exception is thrown in case of errors that cannot be classified with the

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
@@ -4940,6 +4939,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // note erase performs range check
                 parent.erase(json_pointer::template array_index<basic_json_t>(last_path));
             }
+            else
+            {
+                // the parent of a "remove" target must be an object or array
+                // (see #5396)
+                JSON_THROW(out_of_range::create(413, detail::concat("cannot remove value: the JSON Patch 'remove' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
+            }
         };
 
         // type check: top level value must be an array

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
@@ -26429,6 +26367,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // note erase performs range check
                 parent.erase(json_pointer::template array_index<basic_json_t>(last_path));
             }
+            else
+            {
+                // the parent of a "remove" target must be an object or array
+                // (see #5396)
+                JSON_THROW(out_of_range::create(413, detail::concat("cannot remove value: the JSON Patch 'remove' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
+            }
         };
 
         // type check: top level value must be an array

tests/src/unit-class_parser.cpp

@@ -930,94 +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
-                    const std::string wrapped = "[" + number + "," + number + "]";
-                    CHECK(json::accept(wrapped) == expected);
-                }
-            }
         }
     }
 

tests/src/unit-json_patch.cpp

@@ -1389,6 +1389,61 @@ TEST_CASE("JSON patch - add to a primitive parent (regression #4292)")
     }
 }
 
+TEST_CASE("JSON patch - remove with primitive or null parent (regression #5396)")
+{
+    // Regression test for https://github.com/nlohmann/json/issues/5396
+    //
+    // RFC 6902 (§4.2) requires the target location of a "remove" operation
+    // to exist. When the target's parent resolves to a primitive value or
+    // null, the operation must fail. Previously operation_remove silently
+    // did nothing in this case (neither the "is_object" nor the "is_array"
+    // branch matched, and there was no final "else"), so the patch appeared
+    // to succeed without changing the document. It now throws
+    // out_of_range.413.
+
+    SECTION("parent is a primitive (number)")
+    {
+        json const doc = {{"a", 1}};
+        json const patch = {{{"op", "remove"}, {"path", "/a/b"}}};
+#if JSON_DIAGNOSTICS
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] (/a) cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array", json::out_of_range&);
+#else
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array", json::out_of_range&);
+#endif
+    }
+
+    SECTION("parent is a primitive (string)")
+    {
+        json const doc = {{"foo", {{"bar", "a string"}}}};
+        json const patch = {{{"op", "remove"}, {"path", "/foo/bar/baz"}}};
+#if JSON_DIAGNOSTICS
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] (/foo/bar) cannot remove value: the JSON Patch 'remove' target's parent is of type string, but must be an object or array", json::out_of_range&);
+#else
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type string, but must be an object or array", json::out_of_range&);
+#endif
+    }
+
+    SECTION("top-level document is null")
+    {
+        json const doc = nullptr;
+        json const patch = {{{"op", "remove"}, {"path", "/a"}}};
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type null, but must be an object or array", json::out_of_range&);
+    }
+
+    SECTION("legitimate removes still work")
+    {
+        // object member
+        json const doc1 = {{"a", 1}, {"b", 2}};
+        json const patch1 = {{{"op", "remove"}, {"path", "/a"}}};
+        CHECK(doc1.patch(patch1) == json({{"b", 2}}));
+
+        // array element
+        json const doc2 = R"([1, 2, 3])"_json;
+        json const patch2 = {{{"op", "remove"}, {"path", "/1"}}};
+        CHECK(doc2.patch(patch2) == R"([1, 3])"_json);
+    }
+}
+
 TEST_CASE("JSON patch - diff emits array removals in descending index order")
 {
     SECTION("array shrunk to empty")