Disappearing comments with LexicalPreservingPrinter

[andrecsilva]

Moving statements may make their associated comments disappear from LexicalPreservingPrinter output.
An example:

    String code =
        """
    class A{
	    void f(){
		    // first comment
		    int a = 1;
		    // second comment
		    int b = 2;
		    // third comment
		    int c = 3;
	    }
    }
    """;
    CompilationUnit cu = StaticJavaParser.parse(code);
    LexicalPreservingPrinter.setup(cu);

    System.out.println(cu);
    System.out.println("----------------------------------");
    System.out.println(LexicalPreservingPrinter.print(cu));
    var block = cu.findAll(BlockStmt.class).get(0);
    var lastStmt = block.getStatements().removeLast();
    block.addStatement(lastStmt);

    System.out.println("AFTER-----------------------------");
    System.out.println(cu);
    System.out.println("----------------------------------");
    System.out.println(LexicalPreservingPrinter.print(cu));

Output:

    class A {

        void f() {
            // first comment
            int a = 1;
            // second comment
            int b = 2;
            // third comment
            int c = 3;
        }
    }

    ----------------------------------
    class A{
     void f(){
      // first comment
      int a = 1;
      // second comment
      int b = 2;
      // third comment
      int c = 3;
     }
    }

    AFTER-----------------------------
    class A {

        void f() {
            // first comment
            int a = 1;
            // second comment
            int b = 2;
            // third comment
            int c = 3;
        }
    }

    ----------------------------------
    class A{
     void f(){
      // first comment
      int a = 1;
      // second comment
      int b = 2;
      int c = 3;

     }
    }

Notice the last comment is present with the default printer, but won't be printed with the LexicalPreservingPrinter. There is also an extra empty line at the end of the block.

[jlerbsc]

It's a complicated case and I'm surprised that you're the first person to spot this issue. Unfortunately I'm not going to be able to solve it immediately. No matter how much I think about it, I can't see how to display the comment with the LexicalPreservingPrinter.