Support asymmetric comparison between ESM::RefId and std::string_view

apps/openmw_test_suite/esm/testrefid.cpp

@@ -3,6 +3,7 @@
 #include <gtest/gtest.h>
 
 #include <functional>
+#include <map>
 #include <string>
 
 namespace ESM
@@ -122,5 +123,26 @@ namespace ESM
             const std::string_view b = "B";
             EXPECT_LT(a, b);
         }
+
+        TEST(ESMRefIdTest, hasCaseInsensitiveStrongOrderWithStringView)
+        {
+            const RefId a = RefId::stringRefId("a");
+            const std::string_view b = "B";
+            const RefId c = RefId::stringRefId("c");
+            EXPECT_LT(a, b);
+            EXPECT_LT(b, c);
+        }
+
+        TEST(ESMRefIdTest, canBeUsedAsMapKeyWithLookupByStringView)
+        {
+            const std::map<ESM::RefId, int, std::less<>> map({ { ESM::RefId::stringRefId("a"), 42 } });
+            EXPECT_EQ(map.count("A"), 1);
+        }
+
+        TEST(ESMRefIdTest, canBeUsedAsLookupKeyForMapWithStringKey)
+        {
+            const std::map<std::string, int, std::less<>> map({ { "a", 42 } });
+            EXPECT_EQ(map.count(ESM::RefId::stringRefId("A")), 1);
+        }
     }
 }

components/esm/refid.cpp

@@ -16,9 +16,14 @@ namespace ESM
         return Misc::StringUtils::ciLess(mId, rhs.mId);
     }
 
-    bool RefId::operator<(std::string_view rhs) const
+    bool operator<(const RefId& lhs, std::string_view rhs)
     {
-        return Misc::StringUtils::ciLess(mId, rhs);
+        return Misc::StringUtils::ciLess(lhs.mId, rhs);
+    }
+
+    bool operator<(std::string_view lhs, const RefId& rhs)
+    {
+        return Misc::StringUtils::ciLess(lhs, rhs.mId);
     }
 
     std::ostream& operator<<(std::ostream& os, const RefId& refId)

components/esm/refid.hpp

@@ -39,7 +39,9 @@ namespace ESM
 
         bool operator<(const RefId& rhs) const;
 
-        bool operator<(std::string_view rhs) const;
+        friend bool operator<(const RefId& lhs, std::string_view rhs);
+
+        friend bool operator<(std::string_view lhs, const RefId& rhs);
 
         friend std::ostream& operator<<(std::ostream& os, const RefId& dt);