(Cross post from https://discuss.ocaml.org/t/using-merlin-with-camlp5/7082)

I created demo project where I use external preprocess for a library and PPX-based one. Both seems to create files with contents type "OCaml abstract syntax tree implementation file (Version 027)" but for custom preprocessor merlin can't read the generated file. It looks like that it tries to parse it as plain text file.

Using automatically compiled PPX rewriter doesn't raise that error.

Any idea where the issue can be?