How to include contents of a directory in Ocaml?

Question

How do you include a file's content / module from a directory in Ocaml ?

└── bin
    ├── file_1.ml
    └── directory
        └── file_2.ml

In this example, how do you access file_2 contents in file_1.

I can't figure it out, even though it seems trivial.

Answer 1

You can use include_subdirs to signal to dune that you wish to include subdirectories:

└── bin
    ├── dune
    ├── file_1.ml
    └── directory
         └── file_2.ml

There two different mode of inclusion, unqualified inclusion

; bin/dune file
(include_subdirs unqualified)
(executable (name file_1))

that make all modules from subdirectories available in the main directory namespace:

(* bin/file_1.ml *)
module F2 = File_2

or qualified inclusion

; bin/dune file
(include_subdirs qualified)
(executable (name file_1))

that makes modules from subdirectory at path a/b/c available as A.B.C.File_name:

(* bin/file_1.ml *)
module F2 = Directory.File_2

Another possibility to bind directory contents with dune is to make the directory a local library:

└── bin
    ├── dune
    ├── file_1.ml
    └── local_lib_dir
         ├── dune
         └── file_2.ml

where the dune file for bin is

; bin/dune
(executable 
  (name file_1)
  (libraries local_lib)
)

and the one in the local directory is

; bin/local_lib_dir/dune
(library 
  (name local_lib)
)

Then one can use the module defined by file_2 with

(* bin/file_1.ml *)
module F2 = Local_dir.File_2

inside the bin directory.