created: 20130826122000000
modified: 20131214094840608
tags: mechanism
title: PluginMechanism
type: text/vnd.tiddlywiki

[[Plugins]] are bundles of tiddlers that are distributed and managed as a single unit by being packed into a single JSON tiddler. If a tiddler isn't found in the main store, then the registered plugins are searched for it instead.

Tiddlers within plugins behave something like shadow tiddlers in classic TiddlyWiki: they can be freely overwritten by creating a tiddler with the same title, but deleting that tiddler restores the underlying tiddler value from the plugin.

Plugins have a `plugin-type` field that may be:

* `plugin` //(default)// - a plain plugin
* `theme` - a theme plugin (see ThemeMechanism)

Plugins can be used to package ordinary content, or can include JavaScript [[modules|Modules]] that extend and enhance the core TiddlyWiki5 functionality.

Plugins conventionally have a title of the form `$:/plugins/publisher/name`. Plugins that are part of the core TiddlyWiki distribution have titles of the form `$:/plugins/tiddlywiki/name`.

Plugins that define macros, views or other named entities are expected to prefix the name with their publisher identifier, for example: `tiddlytools.slider`.

! Plugin fields

Plugins are stored as tiddlers with the following fields:

|!Field |!Description |
|title |Title of plugin |
|description |Description of plugin |
|author |Author of plugin |
|version |Version string (must conform to SemanticVersioning convention) |
|source |Source URL of plugin |
|type |Must be ''application/json'' |
|plugin-type |Can be ''plugin'' (default) or ''theme'' |
|text |JSON encoding of the list of tiddlers comprising the plugin |
|dependents |List of dependent plugins (currently only implemented for themes) |

! Plugin folders

On the server, plugins can be stored as ordinary JSON tiddlers but it is often more convenient to store them as separate tiddler files within folders. Plugin folders must contain a `plugin.info` file that contains the metadata for the plugin. It can also optionally identify files external to the plugin folder that should be loaded as tiddlers.

The `plugin.info` file should contain the following JSON structure:

The JSON structure for plugin tiddlers is as follows:

```
{
	"title": "$:/plugins/publisher/name",
	"description": "An exemplary plugin for demonstration purposes",
	"author": "JeremyRuston",
	"version": "1.2.3-alpha3",
	"core-version": ">=5.0.0",
	"source": "http://tiddlywiki.com/MyPlugin",
	"plugin-type": "plugin"
}
```

By convention, the titles of the individual tiddlers are prefixed with the title of the containing plugin, but they are not restricted to do so.

Note that if the `version` field is omitted from a `plugin.info` file when the plugin folder is packed then it is automatically filled in by the core to the current core version number. This is to ensure that all the core plugins carry the correct version number. Generally plugin authors will want to ensure that they do explicitly specify a version number.

! Plugin library

The standard distribution of TiddlyWiki includes a number of standard plugins in the `plugins` directory.

! Including plugins in a wiki

To be usable in the browser, plugins just need to be included in the wiki. For wikis that are generated on the server, TiddlyWikiFolders can contain a `tiddlywiki.info` file that identifies the plugins to be included in this wiki:

```
{
	"plugins": [
		"tiddlywiki/slider",
		"tiddlytools/chooser"
	]
}
```

Plugins names refer to plugin folders listed in TiddlyWiki5's root `plugins` folder.

Plugins can also be included manually by copying them into the `plugins` subfolder of the wiki.

! Plugin processing

The wiki object keeps track of all of the currently loaded plugins. If a request for a tiddler isn't in the store then the wiki looks through the cascade of plugins to find the requested tiddler. It is a similar idea to the way that shadow tiddlers are implemented in classic TiddlyWiki.

In the browser, any constituent tiddlers that are JavaScript modules (ie shadow tiddlers of content type `application/javascript` and possessing the field `module-type`) are executed during startup processing.