plugins

Contributing a Plugin

Plugins make it easier to get started with packages that require additional setup when installed with Nix, and they offer a familiar interface for configuring packages. They also help keep all of your project's configuration within your project directory, which helps maintain portability and isolation.

Getting Started

Before writing a plugin, we recommend reading the User Documentation on plugins, as well as inspecting and testing a few of the plugins in this directory. Note that the plugins in this directory are compiled into the Codex binary, but your plugin can be sourced from a local directory or from within your project.

If you're looking for plugin ideas, check out our Issues page for any user requests.

Before contributing, please consult our Contributing Guide and Code of Conduct for details on how to contribute to Codex.

Testing your Plugin

1. Create a new codex.json in an empty directory using codex init.
2. Add your plugin to the include section of the codex.json file. Add any expected packages using codex add <pkg>.
3. Check that your plugin creates the correct files and environment variables when running codex shell
4. If you are looking for sample projects to test your plugin with, check out our examples.

Plugin Design

Plugins are defined as Go JSON Template files, using the following schema:

{
  "name": "",
  "version": "",
  "description": "",
  "env": {
    "<key>": "<value>"
  },
  "create_files": {
    "<destination>": "<source>"
  },
  "init_hook": [
    "<bash commands>"
  ]
}

A plugin can define services by adding a process-compose.yaml file in its create_files stanza.

Plugin Lifecycle

Plugins are activated whenever a developer runs codex shell, runs a script with codex run, or starts a service using codex services start|restart. The lifecycle of a codex shell with plugins works as follows:

---
title: Codex Shell Lifecycle
---
flowchart TD
   A[Plugin env] --> B
   B[User env] --> C
   C[Plugin init_hook] --> D[User Init Hook]
   D -->  E{Start Shell}
   E --> F & G & H
   F[Interactive Shell]
   G[Run Scripts]
   H[Start Services]

Template Placeholders

Codex's Plugin System provides a few special placeholders that should be used when specifying paths for env variables and helper files:

• {{ .CodexDirRoot }} – points to the root folder of their project, where the user's codex.json is stored.
• {{ .CodexDir }} – points to <projectDir>/codex.d/<plugin.name>. This directory is public and added to source control by default. This directory is not modified or recreated by Codex after the initial package installation. You should use this location for files that a user will want to modify and check-in to source control alongside their project (e.g., .conf files or other configs).
• {{ .Virtenv }} – points to <projectDir>/.codex/virtenv/<plugin_name> whenever the plugin activates. This directory is hidden and added to .gitignore by default You should use this location for files or variables that a user should not check-in or edit directly. Files in this directory should be considered managed by Codex, and may be recreated or modified after the initial installation.

Fields

name string

The name of your plugin. This is used to identify your plugin when a user runs codex info. If match is not set, the plugin will automatically activate when a package is added to a codex.json project that matches name.

version string

The version of your plugin. You should start your version at 0.0.1 and bump it whenever you merge an update to the plugin.

match string

A regex expression that is used to identify when the plugin will be activated. Codex will activate your plugin when a package installed with codex add matches this regular expression.

The regex you provide should match a package name. You can look up packages at nixhub.io

readme string

Special usage instructions or notes to display when your plugin activates or when a user runs codex info. You do not need to document variables, helper files, or services, since these are automatically printed when a user runs codex info.

env object

A map of "key" : "value" pairs used to set environment variables in codex shell when the plugin is activated. These variables will be printed when a user runs codex info, and can be overridden by a user's codex.json.

create_files object

A map of "destination":"source" pairs that can be used to create or copy files into the user's codex directory when the plugin is activated. For example:

"create_files": {
    "{{ .CodexDir }}/Caddyfile": "caddy/Caddyfile"
}

Will copy the Caddyfile in the plugins/caddy folder to codex.d/caddy/Caddyfile in the user's project directory.

You should use this to copy starter config files or templates needed to run the plugin's package.

init_hook string | string[]

A single bash command or list of bash commands that should run before the user's shell is initialized. This will run every time a shell is started, so you should avoid any resource heavy or long running processes in this step.

Adding Services

Codex uses Process Compose to run services and background processes.

Plugins can add services to a user's project by adding a process-compose.yaml file to the create_files stanza. This file will be automatically detected by Codex, and started when a user runs codex services up or codex services start.

See the process compose docs for details on how to write define services in process-compose.yaml. You can also check the plugins in this directory for examples on how to write services.

Tips for Writing Plugins

• Only add plugins for packages that require configuration to work with Codex.
• Plugins should try to use the same configuration conventions (environment variables, configuration files) as their packages. This lets developers configure their packages in a way that they are familiar with, using existing documentation.
• If you think a user may want to override or change a parameter, define it as an environment variable in env. This makes it possible for a developer to override the parameter in their codex.json file
• If you're adding a helper file that you think a developer would want check into source control, create it in {{ .CodexDir }}. If you're creating a file that would not be checked into source control, create it in {{ .Virtenv }}.
• Unless there is a very good reason, we do not recommend creating files outside of {{ .CodexDir }} or {{ .Virtenv }}. This helps keep user projects clean and well organized.