From 5fe8b92951581e46953b196fea36a9a4d19f810f Mon Sep 17 00:00:00 2001
From: Florian Albrechtskirchinger <falbrechtskirchinger@gmail.com>
Date: Sun, 7 Aug 2022 09:43:42 +0200
Subject: [PATCH] Make json_pointer usable as map key

---
 include/nlohmann/detail/json_pointer.hpp | 24 ++++++++++++++++++++++--
 single_include/nlohmann/json.hpp         | 24 ++++++++++++++++++++++--
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/include/nlohmann/detail/json_pointer.hpp b/include/nlohmann/detail/json_pointer.hpp
index 28de45028..ce593e843 100644
--- a/include/nlohmann/detail/json_pointer.hpp
+++ b/include/nlohmann/detail/json_pointer.hpp
@@ -847,7 +847,7 @@ class json_pointer
     }
 
   public:
-#ifdef JSON_HAS_CPP_20
+#if JSON_HAS_THREE_WAY_COMPARISON
     /// @brief compares two JSON pointers for equality
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
     template<typename RefStringTypeRhs>
@@ -862,6 +862,13 @@ class json_pointer
     {
         return *this == json_pointer(rhs);
     }
+
+    /// @brief 3-way compares two JSON pointers
+    template<typename RefStringTypeRhs>
+    std::strong_ordering operator<=>(const json_pointer<RefStringTypeRhs>& rhs) const noexcept // *NOPAD*
+    {
+        return  reference_tokens <=> rhs.reference_tokens; // *NOPAD*
+    }
 #else
     /// @brief compares two JSON pointers for equality
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
@@ -904,6 +911,12 @@ class json_pointer
     // NOLINTNEXTLINE(readability-redundant-declaration)
     friend bool operator!=(const StringType& lhs,
                            const json_pointer<RefStringTypeRhs>& rhs);
+
+    /// @brief compares two JSON pointer for less-than
+    template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+    // NOLINTNEXTLINE(readability-redundant-declaration)
+    friend bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
+                          const json_pointer<RefStringTypeRhs>& rhs) noexcept;
 #endif
 
   private:
@@ -911,7 +924,7 @@ class json_pointer
     std::vector<string_t> reference_tokens;
 };
 
-#ifndef JSON_HAS_CPP_20
+#if !JSON_HAS_THREE_WAY_COMPARISON
 // functions cannot be defined inside class due to ODR violations
 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
@@ -958,6 +971,13 @@ inline bool operator!=(const StringType& lhs,
 {
     return !(lhs == rhs);
 }
+
+template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+inline bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
+                      const json_pointer<RefStringTypeRhs>& rhs) noexcept
+{
+    return lhs.reference_tokens < rhs.reference_tokens;
+}
 #endif
 
 NLOHMANN_JSON_NAMESPACE_END
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index beee0136c..578fbc9b7 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -14449,7 +14449,7 @@ class json_pointer
     }
 
   public:
-#ifdef JSON_HAS_CPP_20
+#if JSON_HAS_THREE_WAY_COMPARISON
     /// @brief compares two JSON pointers for equality
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
     template<typename RefStringTypeRhs>
@@ -14464,6 +14464,13 @@ class json_pointer
     {
         return *this == json_pointer(rhs);
     }
+
+    /// @brief 3-way compares two JSON pointers
+    template<typename RefStringTypeRhs>
+    std::strong_ordering operator<=>(const json_pointer<RefStringTypeRhs>& rhs) const noexcept // *NOPAD*
+    {
+        return  reference_tokens <=> rhs.reference_tokens; // *NOPAD*
+    }
 #else
     /// @brief compares two JSON pointers for equality
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
@@ -14506,6 +14513,12 @@ class json_pointer
     // NOLINTNEXTLINE(readability-redundant-declaration)
     friend bool operator!=(const StringType& lhs,
                            const json_pointer<RefStringTypeRhs>& rhs);
+
+    /// @brief compares two JSON pointer for less-than
+    template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+    // NOLINTNEXTLINE(readability-redundant-declaration)
+    friend bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
+                          const json_pointer<RefStringTypeRhs>& rhs) noexcept;
 #endif
 
   private:
@@ -14513,7 +14526,7 @@ class json_pointer
     std::vector<string_t> reference_tokens;
 };
 
-#ifndef JSON_HAS_CPP_20
+#if !JSON_HAS_THREE_WAY_COMPARISON
 // functions cannot be defined inside class due to ODR violations
 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
@@ -14560,6 +14573,13 @@ inline bool operator!=(const StringType& lhs,
 {
     return !(lhs == rhs);
 }
+
+template<typename RefStringTypeLhs, typename RefStringTypeRhs>
+inline bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
+                      const json_pointer<RefStringTypeRhs>& rhs) noexcept
+{
+    return lhs.reference_tokens < rhs.reference_tokens;
+}
 #endif
 
 NLOHMANN_JSON_NAMESPACE_END