package dune-deps

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Show dependency graph of a multi-component dune project


Dune Dependency






Dune-deps scans a dune project and produces a dependency graph which can be rendered with 'dot'. It is useful for projects that define multiple libraries or executables. It allows the developer to visualize the dependencies between the various components of a project.

Published: 04 Jun 2021



Show internal dependencies in your OCaml/Reason/Dune project.

Input: the root folder of your project

Output: a graph in the dot format


$ 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

Rendering the graph

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.

Usage scenarios

How big is this project?

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 file, is:

![project dependencies](deps.png)

You can have this graph automatically created and updated if your project is hosted on GitHub. All you have to do is copy a config file into your project.

How are these specific components related?

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

What uses or is used by a specific component?

The --hourglass or -h option restricts the graph to the dependencies and reverse dependencies of the specified libraries. This is useful to eliminate independent components that may clutter the view.

This example restricts the graph to the dependencies and reverse dependencies of the opam-client library:

$ dune-deps -h opam-client | tred | dot -Tpng > opam-client.png

Compare this with the full graph of the opam project shown above.

Other options are provided for showing only the dependencies, or only the reverse dependencies. It is also possible to do so for multiple nodes of interest. See dune-deps --help for details.

Is this external dependency really necessary?

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.

Project status

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.

Dependencies (4)

  1. sexplib
  2. ocaml
  3. dune >= "2.1"
  4. cmdliner >= "1.0.0"

Dev Dependencies


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