✅ improved test coverage

As we guarantee proper UTF-8 before, we do not need to cope with it later.

src/json.hpp

@@ -6415,12 +6415,8 @@ class serializer
                     if (ensure_ascii and (s[i] & 0x80 or s[i] == 0x7F))
                     {
                         const auto bytes = bytes_following(static_cast<uint8_t>(s[i]));
-                        if (bytes == std::string::npos)
-                        {
-                            // invalid characters are treated as is, so no
-                            // additional space will be used
-                            break;
-                        }
+                        // invalid characters will be detected by throw_if_invalid_utf8
+                        assert (bytes != std::string::npos);
 
                         if (bytes == 3)
                         {
@@ -6588,12 +6584,8 @@ class serializer
                             (ensure_ascii and (s[i] & 0x80 or s[i] == 0x7F)))
                     {
                         const auto bytes = bytes_following(static_cast<uint8_t>(s[i]));
-                        if (bytes == std::string::npos)
-                        {
-                            // copy invalid character as is
-                            result[pos++] = s[i];
-                            break;
-                        }
+                        // invalid characters will be detected by throw_if_invalid_utf8
+                        assert (bytes != std::string::npos);
 
                         // check that the additional bytes are present
                         assert(i + bytes < s.size());

test/src/unit-regression.cpp

@@ -1309,7 +1309,7 @@ TEST_CASE("regression tests")
     SECTION("issue #838 - incorrect parse error with binary data in keys")
     {
         uint8_t key1[] = { 103, 92, 117, 48, 48, 48, 55, 92, 114, 215, 126, 214, 95, 92, 34, 174, 40, 71, 38, 174, 40, 71, 38, 223, 134, 247, 127 };
-        std::string key1_str(key1, key1 + sizeof(key1)/sizeof(key1[0]));
+        std::string key1_str(key1, key1 + sizeof(key1) / sizeof(key1[0]));
         json j = key1_str;
         CHECK_THROWS_AS(j.dump(), json::type_error);
         CHECK_THROWS_WITH(j.dump(), "[json.exception.type_error.316] invalid UTF-8 byte at index 10: 0x7E");