Proposal: task graph visualization

[emlys]

It's often helpful to have some flowchart-style visualization of data flow through a model. It would be great if taskgraph could generate a basic graph visualization. The dependent_tasks attribute should be enough to produce a dependency graph.

Something like Graphviz and its python wrapper could make this pretty straightfoward.

[phargogh]

I agree, even a basic visualization showing task dependencies and task names would be very helpful! Maybe there would be a way to also show which files are being created from a given task? Sounds useful, but I'm sure we wouldn't want the graphic to have so much information on it that we can't really parse it out.

Down the road, I could see a nice extension of this being interactivity, especially for very large graphs like we can find in some research scripts. I had an issue with the NCI water quality pipeline where there were so many tasks that trying to understand the flow of dependencies in a Snakemake-generated Graphviz graphic (below) was pretty tough! Interactivity that would allow one to see a path through the graph (e.g., mousing over a node and having its ancestor and dependent tasks and paths highlighted) would have been useful to me in NCI.