🚧 WIP for #4552

Author: nlohmann

include/nlohmann/detail/output/serializer.hpp

@@ -529,6 +529,12 @@ class serializer
                             // thus removing/ignoring the invalid characters
                             bytes = bytes_after_last_accept;
 
+                            // fix for #4552
+                            if (error_handler == error_handler_t::ignore)
+                            {
+                                bytes += undumped_chars;
+                            }
+
                             if (error_handler == error_handler_t::replace)
                             {
                                 // add a replacement character

single_include/nlohmann/json.hpp

@@ -18816,6 +18816,12 @@ class serializer
                             // thus removing/ignoring the invalid characters
                             bytes = bytes_after_last_accept;
 
+                            // fix for #4552 - discussion pending
+                            if (error_handler == error_handler_t::ignore)
+                            {
+                                bytes += undumped_chars;
+                            }
+
                             if (error_handler == error_handler_t::replace)
                             {
                                 // add a replacement character

tests/src/unit-regression2.cpp

@@ -995,6 +995,14 @@ TEST_CASE("regression tests 2")
         CHECK(p.x == 1);
         CHECK(p.y == 2);
     }
+
+    SECTION("issue #4552 - UTF-8 invalid characters are not always ignored when dumping with error_handler_t::ignore")
+    {
+        nlohmann::json node;
+        node["test"] = "test\334\005";
+        const auto test_dump = node.dump(-1, ' ', false, nlohmann::json::error_handler_t::ignore);
+        CHECK(test_dump == "{\"test\":\"test\334\\u0005\"}");
+    }
 }
 
 DOCTEST_CLANG_SUPPRESS_WARNING_POP

tests/src/unit-serialization.cpp

@@ -107,7 +107,11 @@ TEST_CASE("serialization")
 
             CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] invalid UTF-8 byte at index 5: 0x34", json::type_error&);
             CHECK_THROWS_AS(j.dump(1, ' ', false, json::error_handler_t::strict), json::type_error&);
-            CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123456\"");
+
+            // see pending discussion at #4452
+            // CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123456\"");
+            CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123\xF1\xB0\x34\x35\x36\"");
+
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"123\xEF\xBF\xBD\x34\x35\x36\"");
             CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"123\\ufffd456\"");
         }