Project Scripts

Overview

Many more complex projects have additional processing that needs to take place periodically (e.g. data import and preparation) or even before/after each render. Project scripts are a way to incorporate this processing into your workflow.

Periodic Scripts

You can use the quarto run command to run a TypeScript, R, Python, or Lua script. For example:

Terminal

quarto run import.py

Available script interpreters for quarto run include:

Language	Interpreter
TypeScript	Deno (embedded in Quarto)
Python	Python from `PATH` (or launcher on Windows)
R	Rscript from `PATH`
Lua	Lua 5.3 (embedded in Pandoc)

Using TypeScript or Lua enables you to create scripts with no additional installation requirements. On the other hand, if your project is already using Python or R then scripts in those languages might be more convenient.

If you are using TypeScript, please be sure to consult the section below on Deno Scripts for additonal details on the Deno standard library and importing external scripts.

Pre and Post Render

You can arrange for one or more scripts to execute before and/or after each render using the pre-render and post-render project options. For example:

project:
  type: website
  pre-render: prepare.py
  post-render: 
    - compress.ts
    - fix-links.py

Note that pre-render and post-render also support arbitrary shell commands. So you could for example use make to do data preparation this way:

project:
  type: website
  pre-render: make prepare

Pre and post render scripts are run with the main project directory.

The following environment variables are passed to pre and post-render scripts (note that all paths are relative to the main project directory):

Variable	Description
`QUARTO_PROJECT_RENDER_ALL`	Set to “1” if this is a render of all files in the project (as opposed to an incremental render or a render for preview). This unset if Quarto is not rendering all files.
`QUARTO_PROJECT_OUTPUT_DIR`	Output directory
`QUARTO_PROJECT_INPUT_FILES`	Newline separated list of all input files being rendered (passed only to `pre-render`)
`QUARTO_PROJECT_OUTPUT_FILES`	Newline separated list of all output files rendered (passed only to `post-render`).

If you have a pre-render step that is expensive, you may want only run it when the entire project is being rendered. Here’s how you would do this in the various supported script languages:

if (!Deno.env.get("QUARTO_PROJECT_RENDER_ALL")) {
  Deno.exit();
}

import os
if not os.getenv("QUARTO_PROJECT_RENDER_ALL"):
  exit()

if (!nzchar(Sys.getenv("QUARTO_PROJECT_RENDER_ALL"))) {
  quit()
}

if not os.getenv("QUARTO_PROJECT_RENDER_ALL") then
  os.exit();
end

Deno Scripts

If you want to create project scripts with TypeScript, quarto run enables you to use the Deno TypeScript interpreter bundled with Quarto. This interpreter also includes the complete Deno standard library. For example, to use the Deno YAML parser you would do this:

import { parse } from "https://deno.land/std/yaml/mod.ts";

const config = parse(Deno.readTextFileSync("_quarto.yml"));

The reference to the Deno encoding library above uses a URL: it’s important to note that in spite of this the library is not downloaded from a remote server (in fact, importing from remote servers is disabled entirely in the Quarto Deno interpreter). Rather, the Deno standard library is shipped with Quarto, making standard library URLs available in an offline cache.

You may come across example code that embeds versions directly in Deno library imports. For example:

import { format } from "https://deno.land/std@0.119.0/datetime/mod.ts";

These version-bound imports will not work with Quarto (as its local standard library cache is populated with unversioned URLs). The correct form of the above import is thus:

import { format } from "https://deno.land/std/datetime/mod.ts";

You may also see examples of Deno code that imports 3rd party libraries directly from URLs. As noted above, this functionality is not available in Quarto Deno scripts. Rather, you should download any external libraries you wish to use, include them with your project source code, and import them using relative file paths.