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Show the internal dependencies in your OCaml/Reason/Dune project.
Input: the root folder of your project
Output: a graph in the dot format
Example:
$ dune-deps | tred | dot -Tpng > deps.png
Running dune-deps on itself gives us this dependency graph:
This is the graph we obtain for the source code of opam, an elaborate project of over 50K lines of code:
From opam:
$ opam update
$ opam install dune-deps
From the git repo:
$ make
$ make test
$ make install
For producing a 2D image of the graph, we rely on the dot
command from Graphviz.
Additionally, it is often desirable to remove excessive edges to make the graph more readable. We consider "excessive" an edge that can be removed without changing the reachability from a node to another. This transformation is called transitive reduction and is performed by tred
, normally installed as part of the Graphviz suite.
Produce a graph for the whole project without knowing anything about it. This graph may be unreadable, but it gives a sense of the project's complexity. Use the canonical command pipeline for this:
$ cd my-project
$ dune-deps | tred | dot -Tpng > deps.png
It can be useful to keep this graph embedded in your rich-text readme. The markdown syntax, for including an image in a README.md
file, is:

As a project grows, its graph becomes wider. Some basic dependencies may be used directly by many components, resulting in many edges all tangled up. Transitive reduction as performed by tred
helps with that but is not always sufficient.
For better results, you can build a graph only for selected components. Specify dune
files or selected subfolders directly on the command line. Something like this:
$ dune-deps src/lib-foo src/lib-bar src/lib-baz | tred | dot -Tpng > deps.png
This is work in progress (see https://github.com/mjambon/dune-deps/issues/5). The idea is to show only the graph nodes that are dependencies or reverse dependencies of a specific node.
You can see this by showing all the direct dependencies, i.e. a plain run without transitive reduction:
$ dune-deps | dot -Tpng > deps.png
The resulting graph can be messy, but the number of arrows pointing to the node of interest should give you the answer you're looking for.
Note that this assumes dune
files are properly written with all the direct dependencies listed. If some code uses a module Foo
directly, the library foolib
providing Foo
must be declared as a dependency. In such case, declare dependencies as (libraries foolib barlib)
even if barlib
itself depends on foolib
.
Dune-deps was initiated by Martin Jambon. It is distributed free of charge under the terms of a BSD license.
Software maintenance takes time, skill, and effort. Please contribute to open-source projects to the best of your ability. Talk to your employer about it today.