Fix string_view::compare to take sizes into account

Author: martinmoene

include/nonstd/string.hpp

@@ -482,7 +482,11 @@ class basic_string_view
 
     string_nodiscard string_constexpr int compare( basic_string_view v ) const string_noexcept
     {
-        return Traits::compare( data(), v.data(), (std::min)(size(), v.size()) );
+        auto const result = Traits::compare( data(), v.data(), (std::min)(size(), v.size()) );
+
+        return result != 0
+            ? result
+            : (size() == v.size()) ? 0 : (size() < v.size()) ? -1 : +1;
     }
 
     string_nodiscard string_constexpr bool          empty()  const string_noexcept { return size_ == 0; }

test/string.t.cpp

@@ -792,24 +792,31 @@ CASE( "split_right: split string into two-element tuple given set of delimiter c
 
 CASE( "compare: negative, zero or positive for lsh is less than, equal to or greater than rhs" )
 {
+    EXPECT( compare("abc", "abc") == 0 );
+    EXPECT( compare("aaa", "abc") != 0 );
     EXPECT( compare("aaa", "abc") <  0 );
     EXPECT( compare("aaa", "abc") <= 0 );
     EXPECT( compare("abc", "abc") <= 0 );
-    EXPECT( compare("abc", "abc") == 0 );
     EXPECT( compare("abc", "aaa") >= 0 );
     EXPECT( compare("abc", "aaa") >  0 );
 
+    EXPECT_NOT( compare("abc", "abcd") == 0 );
+    EXPECT    ( compare("abc", "abcd") != 0 );
+
+    EXPECT( compare(std::string("abc"), std::string("abc")) == 0 );
+    EXPECT( compare(std::string("aaa"), std::string("abc")) != 0 );
     EXPECT( compare(std::string("aaa"), std::string("abc")) <  0 );
     EXPECT( compare(std::string("aaa"), std::string("abc")) <= 0 );
     EXPECT( compare(std::string("abc"), std::string("abc")) <= 0 );
     EXPECT( compare(std::string("abc"), std::string("abc")) == 0 );
     EXPECT( compare(std::string("abc"), std::string("aaa")) >= 0 );
     EXPECT( compare(std::string("abc"), std::string("aaa")) >  0 );
 
+    EXPECT( compare(std17::string_view("abc"), std17::string_view("abc")) == 0 );
+    EXPECT( compare(std17::string_view("aaa"), std17::string_view("abc")) != 0 );
     EXPECT( compare(std17::string_view("aaa"), std17::string_view("abc")) <  0 );
     EXPECT( compare(std17::string_view("aaa"), std17::string_view("abc")) <= 0 );
     EXPECT( compare(std17::string_view("abc"), std17::string_view("abc")) <= 0 );
-    EXPECT( compare(std17::string_view("abc"), std17::string_view("abc")) == 0 );
     EXPECT( compare(std17::string_view("abc"), std17::string_view("aaa")) >= 0 );
     EXPECT( compare(std17::string_view("abc"), std17::string_view("aaa")) >  0 );
 }