port-to-dune

Port to Dune

This command migrates an OCaml project from ocamlbuild/topkg to dune.

Arguments

None - operates on the current directory.

Prerequisites

The command expects to find ocamlbuild artifacts:

• _tags - ocamlbuild compilation flags
• *.mllib files - module lists for libraries
• pkg/pkg.ml - topkg package description (optional)
• pkg/META - findlib metadata (optional)
• opam - package dependencies

Migration Process

1. Analyze Existing Build

Read and parse:

• _tags - Extract package dependencies, compiler flags, thread usage
• *.mllib - Identify libraries and their modules
• pkg/pkg.ml - Find optional libraries and conditions
• pkg/META - Get public library names
• opam - Current dependencies

2. Create dune-project

(lang dune 3.20)
(name <package-name>)
(generate_opam_files true)
; ... rest from existing opam metadata

3. Create Library dune Files

For each library identified from .mllib files:

(library
 (name <library_name>)
 (public_name <package.subname>)
 (libraries <dependencies>))

For optional libraries (from pkg/pkg.ml):

(library
 (name <library_name>)
 (public_name <package.subname>)
 (optional)
 (libraries <dependencies>))

4. Handle Special Cases

Warning suppression (if needed):

(flags (:standard -w -27))

Toplevel init files (excluded from library):

(library
 (name lib_name)
 (modules lib_module)
 (libraries deps))

(install
 (package pkg)
 (section lib)
 (files lib_top_init.ml))

5. Create Test dune Files

(test
 (name test_name)
 (libraries lib_name alcotest))

6. Update opam File

• Rename opam to <package>.opam
• Remove ocamlbuild/topkg dependencies
• Add dune dependency
• Update build commands

7. Cleanup

List files to delete (don't delete automatically):

• _tags
• .merlin
• pkg/pkg.ml
• pkg/META
• *.mllib files
• *.itarget files

Mapping Reference

ocamlbuild	dune
_tags: package(foo)	(libraries foo)
_tags: thread	(libraries threads)
foo.mllib	(library (name foo))
pkg/pkg.ml: Pkg.mllib ~cond:x	(library ... (optional))
pkg/META	Auto-generated by dune