This is a reimplementation of graphmod using a source plugin.

The advantage is that the implementation is simpler and more robust as it doesn't rely on lexing source files are finding files on disk. Instead, we just serialise this information from the internal compiler state to generate the graph.

The plugin is also an example of the design pattern of recording information as the plugin runs and then collating information at the end.

graphmod was originally written by Thomas Halgren and Iavor Diatchki.

In order to run the plugin manually, pass the options appropiately to GHC when compiling your package.

-fplugin=GraphMod -fplugin-opt GraphMod:output

Then, call the graphmod-plugin executable passing the --indir flag to indicate where the plugin stored the information.

graphmod-plugin --indir output

You can this pass this output to dot in order to generate an image or pdf.

In addition, graphmod-plugin takes all the options that the old graphmod executable accepted.

It is recomended to use the plugin with nix which will handle the finalisation and generation steps appropiately. See the default.nix file for how to achieve this.

If you want to try this example then it is strongly recommended to use cachix as otherwise you will build GHC from source.

cachix use mpickering
nix-build