Retrieving error correction tokens

I'm trying to compare the error correction in the libadalang parser with the parser in Emacs Ada mode (and other parsers). One way to do that is to retrieve the token list of the final parse, including "virtual tokens" inserted for error correction, and excluding deleted tokens. Diffing that token list with the similar lists from the other parsers, and with the user-expected "correct" token list, gives a fairly objective measure of error correction.

In doing this for libadalang, I first tried:

   for T in Token_Range (Root (Unit)) loop
      Ada.Wide_Wide_Text_IO.Put_Line (Libadalang.Common.Text (T));
   end loop;

This only gives the "real" tokens; the ones present in the source text.

The diagnostics gives some hints about inserted and deleted tokens, but is not explicit enough for this use.

I don't see any mention of something like virtual tokens in the libadalang specs.

One way to output the list I'm looking for would be to traverse the AST, outputting the tokens implied by the structure. This is a lot of work, although I suspect I can copy code from gnatpp that does mostly the same thing. I can't just use gnatpp; it refuses to output anything when there are syntax errors in the source.

An LSP language server should be able to provide a source edit script for each detected syntax error; if that functionality is in libadalang or ada_language_server somewhere, I could use that.

Is there another way?

NOTE: edited by @raph-amiard for style corrections

Start with the Token_Range and Root (Unit) APIs, then inspect how diagnostics expose inserted or deleted tokens. Compare those capabilities with the AST traversal approach mentioned from gnatpp and with any source-edit support in ada_language_server. Done means a documented way to retrieve final parse tokens, including virtual tokens and excluding deleted tokens.