When `"composite": true` specified in `tsconfig.json`, `extras.diagnostics` becomes an empty array

[pucelle]

I don't know if this is an issue. I can get all the extras.diagnostics after changes composite to false.

In addition, I noticed when work with ts-loader, extras.diagnostics becomes empty too, while using tspc command is OK.

I also find when work with tspc -w, same issue happens.