Tragedy Averted

I almost made a terrible blunder.

See https://github.com/slott56/py-web-tool for some background. This is a "Literate Programming" tool. I started fooling around with this kind of thing back in '05 (maybe even earlier.) This is not the blunder. The whole idea of literate programming is not very popular. I'm a fan of Jupyter{Book} as the state of the art in sophisticated literate programming, if you're interested in it.

In my case, I started this project so long ago, I used docutils. This was long before Sphinx arrived on the scene. I never updated my little project to use Sphinx. The point was to have a kind of pure literate programming tool that could work with a variety of markup languages, including (but not limited to) RST.

Recently, I learned about PlantUML. The idea of a text description of a diagram is appealing. I don't really need to draw it; I just need to specify what's in it and let graphviz do the rest. This tool is very, very cool. You can capture ideas quickly. You can refine and expand on ideas until you reach a point where code makes more sense than a picture of code. 

For some things, you can gather data and draw a picture of things *as they are*. This is particularly valuable for cloud-based infrastructure where a few queries leads to PlantUML source that is depicted very nicely.

Which leads to the idea of Literate Programming including UML diagrams. 

Doesn't sound too difficult. I can create an extension to docutils to introduce a UML directive. The resulting RST would look like this:

..  uml::

    left to right direction
    skinparam actorStyle awesome

    actor "Developer" as Dev
    rectangle PyWeb {
        usecase "Tangle Source" as UC_Tangle
        usecase "Weave Document" as UC_Weave
    }
    rectangle IDE {
        usecase "Create WEB" as UC_Create
        usecase "Run Tests" as UC_Test
    }
    Dev --> UC_Tangle
    Dev --> UC_Weave
    Dev --> UC_Create
    Dev --> UC_Test

    UC_Test --> UC_Tangle

This could be handy to have the diagrams as part of the documentation that tangles the working the code. One source for all of it. 

I started down the path of researching docutils extensions. Got pretty far. Far enough that I had an empty repository and everything. I was about ready to start creating spike solutions.

Then.

[music cue] *duh duh duuuuuuh*

I found that Sphinx already has an extension for PlantUML. I almost started reading the code to see how it worked.

Then I realized how dumb that was. It already works. Why read the code? Why not install it?

I had a choice to make.

1. Continue building my own docutils plug-in.
2. Switch to Sphinx.

Some complications:

• My Literate Programming tool produces RST that *may* not be compatible with Sphinx.
• It's yet another dependency in a tool that started out with zero dependencies. I've added pytest and tox. What next? 

What to do?

I have to say that Git is amazing. I can make a branch for the spike. If it works, pull request. If it doesn't work, delete the branch. This continues to be game-changing to me. I'm old. I remember when we had to back up the whole project directory tree before making this kind of change.

It worked. My tool's RST (with one exception) worked perfectly with Sphinx. The one exception was an obscure directive, .. class:: name, used to provide an HTML class name for the following block. This always should have been the docutils .. container:: name directive. With this fix, we're good to go.

I'm happy I avoided the trap of reimplementing something. Instead of that, I upgraded from "bare" docutils with my own CSS to Sphinx with it's sophisticated templates and HTML Themes.

Diagrams and UML notation

When I started in this business I was given a flowcharting template.

See https://americanhistory.si.edu/collections/object-groups/flowcharting-templates. I'm pretty sure I had one of these: https://americanhistory.si.edu/collections/search/object/nmah_690078.

Since then, things have changed a little.

I fondly recall using the Rational Rose (and an earlier tool that did Rumbaugh OMT diagrams) to create object models.

But these were expensive.

After much searching, I found ArgoUML. This was my go-to-diagrammer of choice for many years. It's available here: https://argouml-tigris-org.github.io.

Then, I wound up using yuml at https://yuml.me/diagram/scruffy/class/draw. This was very nice because there was a source text version of the diagram. It was a high-level code-like description that would lead to a handy picture you could include in documentation.

Heavenly.

Recently, I spent time using draw.io. Start here https://draw.io. You have plain-text source version of the diagram that's Git-friendly. I liked that. It has a lot of UML features, which is very nice, also.

But now. 

I'm using plantUML, and I think it's pretty handy. https://plantuml.com. It's a big-old JAR file that converts text to a diagram. There's no GUI component to this. You describe the image in a source-code like way. Run it through the tool, and you get a picture you can paste into documentation. Like yuml, it has an easy-to-understand high-level text description. I strongly suspect I could walk a Python AST and emit plantUML source as an intermediate language from which pictures can be created.

The Python-Markup tool (https://python-markdown.github.io/extensions/) has a third-party PlantUML plug-in. PyCharm can leverage this to draw while you're editing in the markdown window.

The Fiddly Bits

It's a little fiddly to get all the parts organized properly, but, it really, really does work. You can write technical documentation, with pictures.

• Add the Markdown tool to PyCharm.
• In the preferences for the PyCharm Markdown tool, install and enable PlantUML.
• You can usually use conda to install graphviz as well as installing the plantuml-markdown tools. You can manually run the markdown_py application to create the HTML copies of the .md files. 
• Update your OS environment settings to set the GRAPHVIZ_DOT environment variable to name the conda virtual environment where graphviz was installed. For macOS and Linux users update the ~/.zshrc (or ~/.bashrc) file, depending on which shell is in use. Windows users have my heartfelt sympathy; maybe set the system environment variables.
• You may also need to create a plantuml shell script that's on your PATH. I put it in /usr/local/bin. 

See https://github.com/mikitex70/plantuml-markdown for details on installation.

After all this fussing around, it worked delightfully. I'm a convert to PlantUML.

I suggest the following in each diagram.

skinparam monochrome true
skinparam handwritten false
skinparam shadowing false
hide class circle

You may want to set a more global configuration, but I sometimes want to change the handwritten parameter to true for "draft" diagrams, separate from final. 

tl;dr

You can integrate plantUML with PyCharm to draw pictures while you're editing in the markdown window.

You do have to trust plantUML to draw more-or-less what you want. There are limits, and if you don't like what plantUML is doing, switch to draw.io. If you are flexible, however, it's really, really good.