♻️ allow patch and diff to be used with arbitrary string types (#4536)

include/nlohmann/detail/iterators/iteration_proxy.hpp

@@ -10,7 +10,6 @@
 
 #include <cstddef> // size_t
 #include <iterator> // forward_iterator_tag
-#include <string> // string, to_string
 #include <tuple> // tuple_size, get, tuple_element
 #include <utility> // move
 
@@ -20,19 +19,13 @@
 
 #include <nlohmann/detail/abi_macros.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
+#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {
 
-template<typename string_type>
-void int_to_string( string_type& target, std::size_t value )
-{
-    // For ADL
-    using std::to_string;
-    target = to_string(value);
-}
 template<typename IteratorType> class iteration_proxy_value
 {
   public:

include/nlohmann/detail/string_utils.hpp

@@ -0,0 +1,37 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.11.3
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013 - 2024 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <cstddef> // size_t
+#include <string> // string, to_string
+
+#include <nlohmann/detail/abi_macros.hpp>
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+template<typename StringType>
+void int_to_string(StringType& target, std::size_t value)
+{
+    // For ADL
+    using std::to_string;
+    target = to_string(value);
+}
+
+template<typename StringType>
+StringType to_string(std::size_t value)
+{
+    StringType result;
+    int_to_string(result, value);
+    return result;
+}
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/json.hpp

@@ -52,6 +52,7 @@
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/string_concat.hpp>
 #include <nlohmann/detail/string_escape.hpp>
+#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/output/binary_writer.hpp>
@@ -4702,7 +4703,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         // the valid JSON Patch operations
         enum class patch_operations {add, remove, replace, move, copy, test, invalid};
 
-        const auto get_op = [](const std::string & op)
+        const auto get_op = [](const string_t& op)
         {
             if (op == "add")
             {
@@ -4839,8 +4840,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         for (const auto& val : json_patch)
         {
             // wrapper to get a value for an operation
-            const auto get_value = [&val](const std::string & op,
+            const auto get_value = [&val](const string_t& op,
-                                          const std::string & member,
+                                          const string_t& member,
                                           bool string_type) -> basic_json &
             {
                 // find value
@@ -4874,8 +4875,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             }
 
             // collect mandatory members
-            const auto op = get_value("op", "op", true).template get<std::string>();
+            const auto op = get_value("op", "op", true).template get<string_t>();
-            const auto path = get_value(op, "path", true).template get<std::string>();
+            const auto path = get_value(op, "path", true).template get<string_t>();
             json_pointer ptr(path);
 
             switch (get_op(op))
@@ -4901,7 +4902,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
                 case patch_operations::move:
                 {
-                    const auto from_path = get_value("move", "from", true).template get<std::string>();
+                    const auto from_path = get_value("move", "from", true).template get<string_t>();
                     json_pointer from_ptr(from_path);
 
                     // the "from" location must exist - use at()
@@ -4918,7 +4919,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
                 case patch_operations::copy:
                 {
-                    const auto from_path = get_value("copy", "from", true).template get<std::string>();
+                    const auto from_path = get_value("copy", "from", true).template get<string_t>();
                     const json_pointer from_ptr(from_path);
 
                     // the "from" location must exist - use at()
@@ -4978,7 +4979,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/diff/
     JSON_HEDLEY_WARN_UNUSED_RESULT
     static basic_json diff(const basic_json& source, const basic_json& target,
-                           const std::string& path = "")
+                           const string_t& path = "")
     {
         // the patch
         basic_json result(value_t::array);
@@ -5008,7 +5009,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 while (i < source.size() && i < target.size())
                 {
                     // recursive call to compare array values at index i
-                    auto temp_diff = diff(source[i], target[i], detail::concat(path, '/', std::to_string(i)));
+                    auto temp_diff = diff(source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)));
                     result.insert(result.end(), temp_diff.begin(), temp_diff.end());
                     ++i;
                 }
@@ -5025,7 +5026,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     result.insert(result.begin() + end_index, object(
                     {
                         {"op", "remove"},
-                        {"path", detail::concat(path, '/', std::to_string(i))}
+                        {"path", detail::concat<string_t>(path, '/', detail::to_string<string_t>(i))}
                     }));
                     ++i;
                 }
@@ -5036,7 +5037,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     result.push_back(
                     {
                         {"op", "add"},
-                        {"path", detail::concat(path, "/-")},
+                        {"path", detail::concat<string_t>(path, "/-")},
                         {"value", target[i]}
                     });
                     ++i;
@@ -5051,7 +5052,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 for (auto it = source.cbegin(); it != source.cend(); ++it)
                 {
                     // escape the key name to be used in a JSON patch
-                    const auto path_key = detail::concat(path, '/', detail::escape(it.key()));
+                    const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
 
                     if (target.find(it.key()) != target.end())
                     {
@@ -5075,7 +5076,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     if (source.find(it.key()) == source.end())
                     {
                         // found a key that is not in this -> add it
-                        const auto path_key = detail::concat(path, '/', detail::escape(it.key()));
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
                         result.push_back(
                         {
                             {"op", "add"}, {"path", path_key},

single_include/nlohmann/json.hpp

@@ -5275,7 +5275,6 @@ NLOHMANN_JSON_NAMESPACE_END
 
 #include <cstddef> // size_t
 #include <iterator> // forward_iterator_tag
-#include <string> // string, to_string
 #include <tuple> // tuple_size, get, tuple_element
 #include <utility> // move
 
@@ -5287,6 +5286,46 @@ NLOHMANN_JSON_NAMESPACE_END
 
 // #include <nlohmann/detail/meta/type_traits.hpp>
 
+// #include <nlohmann/detail/string_utils.hpp>
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.11.3
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013 - 2024 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+
+
+#include <cstddef> // size_t
+#include <string> // string, to_string
+
+// #include <nlohmann/detail/abi_macros.hpp>
+
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+template<typename StringType>
+void int_to_string(StringType& target, std::size_t value)
+{
+    // For ADL
+    using std::to_string;
+    target = to_string(value);
+}
+
+template<typename StringType>
+StringType to_string(std::size_t value)
+{
+    StringType result;
+    int_to_string(result, value);
+    return result;
+}
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END
+
 // #include <nlohmann/detail/value_t.hpp>
 
 
@@ -5294,13 +5333,6 @@ NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {
 
-template<typename string_type>
-void int_to_string( string_type& target, std::size_t value )
-{
-    // For ADL
-    using std::to_string;
-    target = to_string(value);
-}
 template<typename IteratorType> class iteration_proxy_value
 {
   public:
@@ -15125,6 +15157,8 @@ NLOHMANN_JSON_NAMESPACE_END
 
 // #include <nlohmann/detail/string_escape.hpp>
 
+// #include <nlohmann/detail/string_utils.hpp>
+
 // #include <nlohmann/detail/meta/cpp_future.hpp>
 
 // #include <nlohmann/detail/meta/type_traits.hpp>
@@ -24249,7 +24283,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         // the valid JSON Patch operations
         enum class patch_operations {add, remove, replace, move, copy, test, invalid};
 
-        const auto get_op = [](const std::string & op)
+        const auto get_op = [](const string_t& op)
         {
             if (op == "add")
             {
@@ -24386,8 +24420,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         for (const auto& val : json_patch)
         {
             // wrapper to get a value for an operation
-            const auto get_value = [&val](const std::string & op,
+            const auto get_value = [&val](const string_t& op,
-                                          const std::string & member,
+                                          const string_t& member,
                                           bool string_type) -> basic_json &
             {
                 // find value
@@ -24421,8 +24455,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             }
 
             // collect mandatory members
-            const auto op = get_value("op", "op", true).template get<std::string>();
+            const auto op = get_value("op", "op", true).template get<string_t>();
-            const auto path = get_value(op, "path", true).template get<std::string>();
+            const auto path = get_value(op, "path", true).template get<string_t>();
             json_pointer ptr(path);
 
             switch (get_op(op))
@@ -24448,7 +24482,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
                 case patch_operations::move:
                 {
-                    const auto from_path = get_value("move", "from", true).template get<std::string>();
+                    const auto from_path = get_value("move", "from", true).template get<string_t>();
                     json_pointer from_ptr(from_path);
 
                     // the "from" location must exist - use at()
@@ -24465,7 +24499,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
                 case patch_operations::copy:
                 {
-                    const auto from_path = get_value("copy", "from", true).template get<std::string>();
+                    const auto from_path = get_value("copy", "from", true).template get<string_t>();
                     const json_pointer from_ptr(from_path);
 
                     // the "from" location must exist - use at()
@@ -24525,7 +24559,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/diff/
     JSON_HEDLEY_WARN_UNUSED_RESULT
     static basic_json diff(const basic_json& source, const basic_json& target,
-                           const std::string& path = "")
+                           const string_t& path = "")
     {
         // the patch
         basic_json result(value_t::array);
@@ -24555,7 +24589,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 while (i < source.size() && i < target.size())
                 {
                     // recursive call to compare array values at index i
-                    auto temp_diff = diff(source[i], target[i], detail::concat(path, '/', std::to_string(i)));
+                    auto temp_diff = diff(source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)));
                     result.insert(result.end(), temp_diff.begin(), temp_diff.end());
                     ++i;
                 }
@@ -24572,7 +24606,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     result.insert(result.begin() + end_index, object(
                     {
                         {"op", "remove"},
-                        {"path", detail::concat(path, '/', std::to_string(i))}
+                        {"path", detail::concat<string_t>(path, '/', detail::to_string<string_t>(i))}
                     }));
                     ++i;
                 }
@@ -24583,7 +24617,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     result.push_back(
                     {
                         {"op", "add"},
-                        {"path", detail::concat(path, "/-")},
+                        {"path", detail::concat<string_t>(path, "/-")},
                         {"value", target[i]}
                     });
                     ++i;
@@ -24598,7 +24632,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 for (auto it = source.cbegin(); it != source.cend(); ++it)
                 {
                     // escape the key name to be used in a JSON patch
-                    const auto path_key = detail::concat(path, '/', detail::escape(it.key()));
+                    const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
 
                     if (target.find(it.key()) != target.end())
                     {
@@ -24622,7 +24656,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     if (source.find(it.key()) == source.end())
                     {
                         // found a key that is not in this -> add it
-                        const auto path_key = detail::concat(path, '/', detail::escape(it.key()));
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
                         result.push_back(
                         {
                             {"op", "add"}, {"path", path_key},

tests/src/unit-alt-string.cpp

@@ -35,10 +35,21 @@ class alt_string
     alt_string(size_t count, char chr): str_impl(count, chr) {}
     alt_string() = default;
 
-    template <typename...TParams>
+    alt_string& append(char ch)
-    alt_string& append(TParams&& ...params)
     {
-        str_impl.append(std::forward<TParams>(params)...);
+        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;
     }
 
@@ -157,6 +168,11 @@ class alt_string
         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)
 
@@ -319,4 +335,28 @@ TEST_CASE("alternative string type")
         CHECK(j.at(alt_json::json_pointer("/foo/0")) == j["foo"][0]);
         CHECK(j.at(alt_json::json_pointer("/foo/1")) == j["foo"][1]);
     }
+
+    SECTION("patch")
+    {
+        alt_json const patch1 = alt_json::parse(R"([{ "op": "add", "path": "/a/b", "value": [ "foo", "bar" ] }])");
+        alt_json const doc1 = alt_json::parse(R"({ "a": { "foo": 1 } })");
+
+        CHECK_NOTHROW(doc1.patch(patch1));
+        alt_json doc1_ans = alt_json::parse(R"(
+                {
+                    "a": {
+                        "foo": 1,
+                        "b": [ "foo", "bar" ]
+                    }
+                }
+            )");
+        CHECK(doc1.patch(patch1) == doc1_ans);
+    }
+
+    SECTION("diff")
+    {
+        alt_json const j1 = {"foo", "bar", "baz"};
+        alt_json const j2 = {"foo", "bam"};
+        CHECK(alt_json::diff(j1, j2).dump() == "[{\"op\":\"replace\",\"path\":\"/1\",\"value\":\"bam\"},{\"op\":\"remove\",\"path\":\"/2\"}]");
+    }
 }