.merline is useful when I want to identify types.
If I build with dune, .merline file seems to be generated automatically however .merline file is not automatically generated when I build with oasis.
How can I get .merlin file with oasis, not dune? because both of are build tools so I’d like to use only one(oasis) build tool that can generate .merlin file.
Thank you!
The community recommendation nowadays is to use dune. If you’re starting a new project, use dune 
If you have an existing project with OASIS, consider porting it to dune. OASIS doesn’t seem to have the ability to generate a .merlin file, there’s an open issue: https://github.com/ocaml/oasis/issues/110 , someone posted a comment there with a shell script that might do the job.
To confirm further, in OASIS days, it was common to commit .merlin files, because they had to be generated separately. They would often go out of sync with the project.