Missing separator between list elements leads to unintended merge

[andymalakov]

We love HOCON relaxed syntax that "allows omitting commas as long as there's a newline". However this may lead to unintended consequences when user accidentally omits both comma and new line characters when enumerating list elements:

  aList = [
          {
              name = "ONE",
          }
          {
              name = "TWO",
          }          {   // <---------- this line will be ignored!
              name = "THREE",
          }
  ]

Expected behavior: some kind of warning or error message indicating that input contains ; sequence that will be ignored.

Actual behavior: objects "TWO" and "THREE" merged.

Java code:

package deltix.ember.app;

import com.typesafe.config.Config;
import com.typesafe.config.ConfigFactory;

public class ObjectLostSample {

    private static final String HOCON = """
            aList = [
                    {
                        name = "ONE",
                    }
                    {
                        name = "TWO",
                    } {                   // this line will be ignored!
                        name = "THREE",
                    }
            ]
            """;

    public static void main (String [] args) {
        Config config = ConfigFactory.parseString(HOCON);

        var aList = config.getObjectList("aList");
        System.out.println("aList size: " + aList.size());
        System.out.println("aList (0): " + aList.get(0));
        System.out.println("aList (1): " + aList.get(1));
    }
}

Prints:

aList size: 2
aList (0): SimpleConfigObject({"name":"ONE"})
aList (1): SimpleConfigObject({"name":"THREE"})