Use only documented StringType members in json_pointer

contains(const json_pointer&) and operator/=(std::size_t) (and hence
operator/(std::size_t)) used string_t operations that the StringType
template parameter documentation explicitly does not require:
comparing string_t with a const char* literal, c_str(), and
constructibility from std::string. This made both functions fail to
compile for a conforming custom StringType, even though the
documentation's own reference StringType satisfies the requirements.

Fix contains() to compare individual chars ('0'..'9') instead of
comparing string_t with const char* literals, and to call data()
(documented to be null-terminated) instead of c_str(). Fix
operator/=(std::size_t) to build the array-index token via the
existing detail::to_string<StringType> helper (ADL int_to_string() or
assignment from std::to_string()) instead of via std::to_string()
directly, matching how diff(), items(), and std::hash already convert
a std::size_t to a StringType.

Add regression tests to tests/src/unit-alt-string.cpp: contains() for
present/missing keys and indices, "-", a leading zero, and a
non-numeric token on an array, plus json_pointer::operator/(std::size_t).

Fixes #5666.

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

docs/mkdocs/docs/api/basic_json/emplace.md

@@ -69,5 +69,3 @@ Logarithmic in the size of the container, O(log(`size()`)).
 ## Version history
 
 - Since version 2.0.8.
-- Fixed in version 3.13.0: for [`ordered_json`](../ordered_json.md), the value could previously only be passed as an
-  rvalue; it can now also be passed as an lvalue or a `#!cpp const` lvalue, matching the behavior of `json`.

docs/mkdocs/docs/features/types/template_parameters.md

@@ -389,6 +389,7 @@ using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
 | Functionality                                                                                                                     | Additional requirement                                                                                                                                                                       |
 |-----------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | [`diff`](../../api/basic_json/diff.md), [`items`](../../api/basic_json/items.md), [`std::hash`](../../api/basic_json/std_hash.md) | conversion of a `#!cpp std::size_t` to `StringType`: either assignability from the result of `#!cpp std::to_string`, or an ADL overload `#!cpp void int_to_string(StringType&, std::size_t)` |
+| [`operator/(std::size_t)`](../../api/json_pointer/operator_slash.md)                                                              | the same conversion of a `#!cpp std::size_t` to `StringType` as `diff`, `items`, and `std::hash` above                                                                                       |
 | [`std::hash<basic_json>`](../../api/basic_json/std_hash.md)                                                                       | additionally a specialization of `#!cpp std::hash<StringType>`                                                                                                                               |
 | [`to_bson`](../../api/basic_json/to_bson.md)                                                                                      | `find(value_type)` and `npos`                                                                                                                                                                |
 | [`parse`](../../api/basic_json/parse.md) from a `string_t`                                                                        | the input adapters must accept it; otherwise pass a character range                                                                                                                          |

include/nlohmann/detail/json_pointer.hpp

@@ -26,6 +26,7 @@
 #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/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -116,7 +117,7 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slasheq/
     json_pointer& operator/=(std::size_t array_idx)
     {
-        return *this /= std::to_string(array_idx);
+        return *this /= detail::to_string<string_t>(array_idx);
     }
 
     /// @brief create a new JSON pointer by appending the right JSON pointer at the end of the left JSON pointer
@@ -746,7 +747,7 @@ class json_pointer
                         // "-" always fails the range check
                         return false;
                     }
-                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !("0" <= reference_token && reference_token <= "9")))
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !('0' <= reference_token[0] && reference_token[0] <= '9')))
                     {
                         // invalid char
                         return false;
@@ -774,7 +775,7 @@ class json_pointer
                     // not throw (see #5395), so such a reference token is treated as "not found"
                     errno = 0; // strtoull() does not reset errno on success
                     char* p_end = nullptr; // NOLINT(misc-const-correctness)
-                    const unsigned long long magnitude = std::strtoull(reference_token.c_str(), &p_end, 10); // NOLINT(runtime/int)
+                    const unsigned long long magnitude = std::strtoull(reference_token.data(), &p_end, 10); // NOLINT(runtime/int)
                     if (JSON_HEDLEY_UNLIKELY(errno == ERANGE // the value exceeds ULLONG_MAX
                                              || magnitude >= static_cast<unsigned long long>((std::numeric_limits<typename BasicJsonType::size_type>::max)()))) // NOLINT(runtime/int)
                     {

include/nlohmann/ordered_map.hpp

@@ -70,9 +70,7 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
         return *this;
     }
 
-    template < class V, detail::enable_if_t <
-                   detail::is_constructible < T, V&& >::value, int > = 0 >
-    std::pair<iterator, bool> emplace(const key_type& key, V && t)
+    std::pair<iterator, bool> emplace(const key_type& key, T&& t)
     {
         for (auto it = this->begin(); it != this->end(); ++it)
         {
@@ -81,14 +79,13 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                 return {it, false};
             }
         }
-        Container::emplace_back(key, std::forward<V>(t));
+        Container::emplace_back(key, std::forward<T>(t));
         return {std::prev(this->end()), true};
     }
 
-    template < class KeyType, class V, detail::enable_if_t <
-                   detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value&&
-                   detail::is_constructible < T, V&& >::value, int > = 0 >
-    std::pair<iterator, bool> emplace(KeyType && key, V && t)
+    template<class KeyType, detail::enable_if_t<
+                 detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
+    std::pair<iterator, bool> emplace(KeyType && key, T && t)
     {
         for (auto it = this->begin(); it != this->end(); ++it)
         {
@@ -97,7 +94,7 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                 return {it, false};
             }
         }
-        Container::emplace_back(std::forward<KeyType>(key), std::forward<V>(t));
+        Container::emplace_back(std::forward<KeyType>(key), std::forward<T>(t));
         return {std::prev(this->end()), true};
     }
 

single_include/nlohmann/json.hpp

@@ -18867,6 +18867,8 @@ NLOHMANN_JSON_NAMESPACE_END
 
 // #include <nlohmann/detail/string_escape.hpp>
 
+// #include <nlohmann/detail/string_utils.hpp>
+
 // #include <nlohmann/detail/value_t.hpp>
 
 
@@ -18958,7 +18960,7 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slasheq/
     json_pointer& operator/=(std::size_t array_idx)
     {
-        return *this /= std::to_string(array_idx);
+        return *this /= detail::to_string<string_t>(array_idx);
     }
 
     /// @brief create a new JSON pointer by appending the right JSON pointer at the end of the left JSON pointer
@@ -19588,7 +19590,7 @@ class json_pointer
                         // "-" always fails the range check
                         return false;
                     }
-                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !("0" <= reference_token && reference_token <= "9")))
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !('0' <= reference_token[0] && reference_token[0] <= '9')))
                     {
                         // invalid char
                         return false;
@@ -19616,7 +19618,7 @@ class json_pointer
                     // not throw (see #5395), so such a reference token is treated as "not found"
                     errno = 0; // strtoull() does not reset errno on success
                     char* p_end = nullptr; // NOLINT(misc-const-correctness)
-                    const unsigned long long magnitude = std::strtoull(reference_token.c_str(), &p_end, 10); // NOLINT(runtime/int)
+                    const unsigned long long magnitude = std::strtoull(reference_token.data(), &p_end, 10); // NOLINT(runtime/int)
                     if (JSON_HEDLEY_UNLIKELY(errno == ERANGE // the value exceeds ULLONG_MAX
                                              || magnitude >= static_cast<unsigned long long>((std::numeric_limits<typename BasicJsonType::size_type>::max)()))) // NOLINT(runtime/int)
                     {
@@ -25832,9 +25834,7 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
         return *this;
     }
 
-    template < class V, detail::enable_if_t <
-                   detail::is_constructible < T, V&& >::value, int > = 0 >
-    std::pair<iterator, bool> emplace(const key_type& key, V && t)
+    std::pair<iterator, bool> emplace(const key_type& key, T&& t)
     {
         for (auto it = this->begin(); it != this->end(); ++it)
         {
@@ -25843,14 +25843,13 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                 return {it, false};
             }
         }
-        Container::emplace_back(key, std::forward<V>(t));
+        Container::emplace_back(key, std::forward<T>(t));
         return {std::prev(this->end()), true};
     }
 
-    template < class KeyType, class V, detail::enable_if_t <
-                   detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value&&
-                   detail::is_constructible < T, V&& >::value, int > = 0 >
-    std::pair<iterator, bool> emplace(KeyType && key, V && t)
+    template<class KeyType, detail::enable_if_t<
+                 detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
+    std::pair<iterator, bool> emplace(KeyType && key, T && t)
     {
         for (auto it = this->begin(); it != this->end(); ++it)
         {
@@ -25859,7 +25858,7 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                 return {it, false};
             }
         }
-        Container::emplace_back(std::forward<KeyType>(key), std::forward<V>(t));
+        Container::emplace_back(std::forward<KeyType>(key), std::forward<T>(t));
         return {std::prev(this->end()), true};
     }
 

tests/src/unit-alt-string.cpp

@@ -343,6 +343,41 @@ TEST_CASE("alternative string type")
         CHECK(j2.flatten().unflatten() == j2);
     }
 
+    SECTION("contains(json_pointer)")
+    {
+        // contains(json_pointer) must compile and work with a string_t that has
+        // no c_str() and no comparison with const char* (see #5666)
+        auto j = alt_json::parse(R"({"foo": ["bar", "baz"]})");
+
+        // present: object key and array indices
+        CHECK(j.contains(alt_json::json_pointer("/foo")));
+        CHECK(j.contains(alt_json::json_pointer("/foo/0")));
+        CHECK(j.contains(alt_json::json_pointer("/foo/1")));
+
+        // missing: absent object key and out-of-range array index
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/bar")));
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/2")));
+
+        // "-" always fails the range check
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/-")));
+
+        // an array index must not have a leading zero
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/01")));
+
+        // a reference token that is not a number
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/bar")));
+    }
+
+    SECTION("operator/(std::size_t)")
+    {
+        // json_pointer::operator/=(std::size_t) must compile without string_t
+        // being constructible from std::string (see #5666)
+        auto j = alt_json::parse(R"({"foo": ["bar", "baz"]})");
+
+        CHECK(j.at(alt_json::json_pointer("/foo") / std::size_t(0)) == j["foo"][0]);
+        CHECK(j.at(alt_json::json_pointer("/foo") / std::size_t(1)) == j["foo"][1]);
+    }
+
     SECTION("patch")
     {
         alt_json const patch1 = alt_json::parse(R"([{ "op": "add", "path": "/a/b", "value": [ "foo", "bar" ] }])");

tests/src/unit-ordered_json.cpp

@@ -196,44 +196,3 @@ TEST_CASE("regression test - diff() must account for ordered_json member order")
         CHECK(a.patch(p) == b);
     }
 }
-
-TEST_CASE("regression test for issue #5673 - ordered_json::emplace with a non-rvalue value")
-{
-    SECTION("lvalue value")
-    {
-        ordered_json oj = ordered_json::object();
-        ordered_json value = 1;
-        auto res = oj.emplace("a", value);
-        CHECK(res.second == true);
-        CHECK(oj.dump() == "{\"a\":1}");
-    }
-
-    SECTION("const lvalue value")
-    {
-        ordered_json oj = ordered_json::object();
-        const ordered_json value = 1;
-        auto res = oj.emplace("a", value);
-        CHECK(res.second == true);
-        CHECK(oj.dump() == "{\"a\":1}");
-    }
-
-    SECTION("rvalue value")
-    {
-        ordered_json oj = ordered_json::object();
-        auto res = oj.emplace("a", ordered_json(1));
-        CHECK(res.second == true);
-        CHECK(oj.dump() == "{\"a\":1}");
-    }
-
-    SECTION("existing key is not overwritten (std::map-compatible semantics)")
-    {
-        ordered_json oj = ordered_json::object();
-        ordered_json value = 1;
-        oj.emplace("a", value);
-
-        ordered_json other_value = 2;
-        auto res = oj.emplace("a", other_value);
-        CHECK(res.second == false);
-        CHECK(oj.dump() == "{\"a\":1}");
-    }
-}

tests/src/unit-ordered_map.cpp

@@ -312,77 +312,4 @@ TEST_CASE("ordered_map")
             CHECK(om.size() == 4);
         }
     }
-
-    SECTION("emplace")
-    {
-        // regression test for issue #5673: the mapped-value parameter must
-        // accept lvalues and const lvalues, not just rvalues
-        ordered_map<std::string, std::string> om;
-        om["eins"] = "one";
-        om["zwei"] = "two";
-        om["drei"] = "three";
-
-        SECTION("with T&& (rvalue)")
-        {
-            auto res1 = om.emplace("eins", std::string("1"));
-            CHECK(res1.first == om.begin());
-            CHECK(res1.second == false);
-            CHECK(om.size() == 3);
-            CHECK(om.at("eins") == "one"); // existing key is not overwritten
-
-            auto res4 = om.emplace("vier", std::string("four"));
-            CHECK(res4.first == om.begin() + 3);
-            CHECK(res4.second == true);
-            CHECK(om.size() == 4);
-            CHECK(om.at("vier") == "four");
-        }
-
-        SECTION("with T& (lvalue)")
-        {
-            std::string one = "1";
-            std::string four = "four";
-
-            auto res1 = om.emplace("eins", one);
-            CHECK(res1.first == om.begin());
-            CHECK(res1.second == false);
-            CHECK(om.size() == 3);
-            CHECK(om.at("eins") == "one"); // existing key is not overwritten
-
-            auto res4 = om.emplace("vier", four);
-            CHECK(res4.first == om.begin() + 3);
-            CHECK(res4.second == true);
-            CHECK(om.size() == 4);
-            CHECK(om.at("vier") == "four");
-            CHECK(four == "four"); // source was copied, not moved from
-        }
-
-        SECTION("with const T&")
-        {
-            const std::string one = "1";
-            const std::string four = "four";
-
-            auto res1 = om.emplace("eins", one);
-            CHECK(res1.first == om.begin());
-            CHECK(res1.second == false);
-            CHECK(om.size() == 3);
-
-            auto res4 = om.emplace("vier", four);
-            CHECK(res4.first == om.begin() + 3);
-            CHECK(res4.second == true);
-            CHECK(om.size() == 4);
-            CHECK(om.at("vier") == "four");
-        }
-
-        SECTION("with key of key_type (non-template overload)")
-        {
-            const std::string key_vier{"vier"};
-            std::string four = "four";
-
-            auto res4 = om.emplace(key_vier, four);
-            CHECK(res4.first == om.begin() + 3);
-            CHECK(res4.second == true);
-            CHECK(om.size() == 4);
-            CHECK(om.at("vier") == "four");
-        }
-    }
 }