DRY Documents: Plugin Use-Case In Jupyter Book & MyST

by Alex Johnson 54 views

Have you ever found yourself repeating the same content blocks across your documents? It's a common challenge in technical writing, and thankfully, tools like Jupyter Book and MyST offer powerful solutions through plugins. This article explores a practical use-case for creating plugins to DRY (Don't Repeat Yourself) your documents, ensuring consistency and maintainability. We'll delve into a real-world example and discuss considerations for plugin development, specifically addressing the nuances of working with Abstract Syntax Trees (AST).

The Problem: Repetitive Content

In many documentation projects, certain elements, such as callouts, warnings, or specific code snippets, need to be repeated across multiple pages. Manually duplicating these elements is not only time-consuming but also prone to errors and inconsistencies. Imagine you're writing a tutorial series, and each tutorial requires a consistent set of instructions or a particular note about software dependencies. If you copy and paste these elements repeatedly, any change to the original element needs to be manually propagated across all instances. This becomes a maintenance nightmare as your project grows.

This is where the DRY principle comes into play. The DRY principle advocates for avoiding redundancy in your code and content. Instead of repeating information, you should aim to define it once and reuse it wherever needed. In the context of documentation, this means finding ways to create reusable components that can be easily inserted into different parts of your project.

Plugins offer a fantastic way to achieve this in Jupyter Book and MyST. By creating a custom plugin, you can define reusable directives or roles that encapsulate the repetitive content. This not only simplifies the writing process but also ensures consistency in the look and feel of your documentation.

A Practical Example: Consistent Callouts

Let's consider a scenario where you want to create consistent callouts in your documentation. Callouts are visually distinct sections that highlight important information, such as tips, notes, or warnings. Suppose you want all your callouts to have a specific style, including a colored background, a unique icon, and a consistent text formatting. Manually creating these callouts each time you need them can be tedious and lead to inconsistencies.

A plugin can solve this problem by defining custom directives for each type of callout (e.g., tip, note, warning). These directives can encapsulate the styling and formatting, allowing you to insert callouts with a simple markup. For example, you might define a tip directive that automatically renders a callout with a green background, a lightbulb icon, and a bold title. This not only simplifies the writing process but also ensures that all tips in your documentation have a consistent appearance.

One practical example of this can be seen in the geojupyter/workshop-open-source-geospatial repository. The author created two directives to provide a consistent appearance and prose for repeated callouts. This demonstrates the ease and effectiveness of using plugins to deduplicate content in MyST documents.

Diving into the Code: Custom Directives

To implement custom directives, you'll typically use the MyST Markdown syntax and the plugin API provided by Jupyter Book and MyST. The process involves defining a directive class that handles the parsing and rendering of the directive. This class will specify the directive's name, its arguments, and the content it should render.

Here's a simplified example of how you might define a tip directive in a plugin:

// Example in JavaScript (MyST plugin)
module.exports = {
  directives: {
    tip: {
      argument_spec: {},
      body: true,
      run: function (data) {
        const text = data.body;
        return `
<div class="tip-callout">
  <strong>Tip:</strong> ${text}
</div>
        `;
      },
    },
  },
};

In this example, the tip directive takes no arguments (argument_spec: {}) and expects a body (body: true). The run function defines how the directive should be rendered. In this case, it wraps the content in a div with the class tip-callout and adds a bold "Tip:" prefix. You would then define the CSS for the tip-callout class to style the callout as desired.

By using this directive, you can easily insert tips into your documentation using the following syntax:

:::{tip}
This is a helpful tip.
:::

This approach significantly reduces redundancy and ensures that all tips have a consistent appearance.

Working with Abstract Syntax Trees (AST)

When developing plugins for MyST and Jupyter Book, you'll often encounter the concept of Abstract Syntax Trees (AST). An AST is a tree-like representation of the structure of your Markdown content. Plugins can manipulate the AST to modify the content before it's rendered. This allows for powerful transformations, such as adding custom elements, modifying existing ones, or even rewriting the content entirely.

MyST plugins can operate on the AST at two different stages: "PRE" AST and "POST" AST. "PRE" AST refers to the AST before MyST's default processing, while "POST" AST refers to the AST after MyST's default processing. This distinction is important because it affects the way you need to interact with the AST.

Working with "PRE" AST can be more concise because you're dealing with the raw Markdown structure before any transformations have been applied. However, it also requires a deeper understanding of the MyST Markdown syntax and the AST structure. Working with "POST" AST, on the other hand, allows you to leverage MyST's built-in processing, but it can also be more complex because the AST has already been transformed.

In the example mentioned earlier, the author initially wanted to work with "PRE" AST for its conciseness but found that they had to use "POST" AST to get the desired result. This raises an interesting question about whether there's a way to simplify the process of working with "PRE" AST. Ideally, a function or utility could be provided to plugin authors that abstracts away some of the complexities of "PRE" AST manipulation.

The Question: Simplifying "PRE" AST Manipulation

The core question here is: Is there a way to enable plugin authors to write plugins that only deal with "PRE" AST, potentially by providing a function or utility that simplifies the process?

This is a valid concern because working with "PRE" AST can be challenging due to the raw nature of the AST structure. Plugin authors often need to navigate complex tree structures and understand the intricacies of the MyST Markdown syntax. A utility that simplifies this process could significantly reduce the learning curve and make plugin development more accessible.

One possible approach is to provide a function that allows plugin authors to register handlers for specific Markdown elements. These handlers would be invoked when the corresponding element is encountered in the "PRE" AST, allowing the plugin author to modify the element as needed. This would abstract away the need to directly manipulate the AST, making the process more intuitive.

Another approach is to provide a set of helper functions that perform common AST manipulations, such as inserting elements, modifying attributes, or deleting nodes. These functions could encapsulate the low-level details of AST manipulation, allowing plugin authors to focus on the higher-level logic of their plugins.

Benefits of DRYing Documents with Plugins

Using plugins to DRY your documents offers several significant benefits:

  • Consistency: Ensures a consistent look and feel across your entire documentation project.
  • Maintainability: Simplifies maintenance by allowing you to update reusable components in one place.
  • Reduced Redundancy: Eliminates the need to repeat the same content blocks, saving time and effort.
  • Improved Readability: Makes your documentation easier to read and understand by presenting information in a consistent manner.
  • Enhanced Collaboration: Facilitates collaboration by providing a shared set of reusable components.

By leveraging the power of plugins, you can create documentation that is not only informative but also well-structured, consistent, and easy to maintain.

Conclusion

DRYing your documents with plugins is a powerful technique for creating high-quality documentation. By defining reusable components, you can ensure consistency, reduce redundancy, and simplify maintenance. While working with Abstract Syntax Trees (AST) can be challenging, the benefits of plugin development far outweigh the complexities. As the MyST and Jupyter Book ecosystems continue to evolve, we can expect to see even more tools and utilities that simplify the plugin development process.

If you're interested in learning more about MyST and Jupyter Book, I highly recommend checking out the official documentation on the MyST-Parser documentation. It's a fantastic resource for understanding the underlying concepts and exploring the full range of features offered by these tools.