dependson: A Quarto Experiment on Dependencies

The dependson extension is an experiment designed to explore variables and functions between Lua filters in the Quarto document generation system. This functionality can be useful within a single extension or even across different extensions.

Usage

It's important to note that the dependson extension doesn't introduce any significant improvements to your document content. Instead, it serves as a valuable example of how to reuse code and share variables and functions between different Lua filters.

Installation

To install the dependson extension, open your terminal and execute the following command:

quarto add coatless-quarto/dependson

This command will download and install the extension under the _extensions subdirectory of your Quarto project. If you're using version control, make sure to include this directory in your repository.

Nesting Extensions

Let's explore a folder structure that demonstrates the versatility of the dependson extension:

.
├── example.qmd
├── _extensions
│   └── dependson
│       ├── dependson.lua
│       ├── _extensions
│       │   └── coatless-quarto
│       │       └── thedependency
│       │           ├── _extension.yml
│       │           └── thedependency.lua
│       ├── _extension.yml
│       ├── next-level
│       │   └── nested.lua
│       └── same-directory.lua
└── README.md

In this directory structure:

1. The dependson extension consists of multiple Lua files located in different directories.
2. We have an extension called thedependency nested within the main dependson extension.

Now, let's see how we can retrieve values from the next-level/nested.lua module and the thedependency extension.

Retrieving Values from Lua Modules

To retrieve global variables (excluding those declared with the local keyword), you can use the require function to load the lua file containing the variable. In this example, the dependson.lua extension loads the same-level.lua module with require("same-level") and the nested.lua module using require("next-level/nested.lua"). This makes available the globally defined variables for output.

-- Check global variable definitions (e.g. no local prefixed to variable)

-- Check to see if the nested value is present in the global space
local my_level = require("same-directory")

-- Check to see if the same value is present
quarto.log.output(same_level_value)

Retrieving Values from Extensions

For extensions, you can access functions as follows:

-- Store function calls in a table value
local dependency = require("_extensions.coatless-quarto.thedependency.thedependency")

-- Call the function defined in the separate Lua file
dependency.check_function()

This code demonstrates how to import and use functions defined in the thedependency extension within your Lua code.

Fin

By using these techniques, you can efficiently share code and data between different parts of your Quarto extensions.