Help:TemplateData

TemplateData is a way of storing information about a template (such as parameter names, or a description of the template) so that the VisualEditor can retrieve and use it to populate the template editor, thus making it easier to edit templates.

TemplateData allows users to write small bits of structured data to a template page, or to be transcluded into that template page (such as on the standard documentation page). Once a template has this structured data, it can be displayed properly in the VisualEditor. While this may sound complex, it's actually very easy.

The structure of TemplateData
TemplateData's structure is based around the "JSON" standard, and is fairly simple. The first thing to do is to type out a pair of tags, anywhere on the template's /doc subpage, like so:

TemplateData goes here

This tells the software that everything between the two tags is TemplateData, and should be referenced when the template is used. The TemplateData itself follows a standard layout; let's say that you have a template called "Commons" for linking to a commons category about an article. It has one parameter, and that is the name of the commons category. The TemplateData would look something like:

This would display, in the template, like so: {       "description": "A template for linking to a commons category about an article", "params": { "1": {                       "label": "Commons category", "description": "The commons category you want to link to.", "type": "string", "required": true }       } }

What it all means
So let's break that down. The first tag is a "description", which is fairly self-explanatory; it describes what the template does. There is then a "params" tag, which indicates that subsequent sections cover each parameter in the template.

Within each subsection, the first tag is the name of the template parameter within the template - if the parameter is simply called "1", this tag would be "1". Next we have "label", in which you put a human-readable title for the parameter that will be displayed within the template editor. We then have "description" - this time a description of the parameter, not of the template as a whole. After that we have "type", which controls how the template editor will interpret that parameter. This can be "string" (a set of characters, like this sentence!), "number" (a set of digits), "string/wiki-user-name" or "string/wiki-page-name". We then have "required", which can be set to either true or false; this simply controls whether filling out the parameter is mandatory for that template.

If you have multiple parameters, just repeat each section (starting from the "1" tag) and fill it out as you see fit. Once you're done, hit "save". If you've made errors, it will not let you save - which we appreciate is disruptive, but means you can't break anything. Should you run into errors, explain on the feedback page what you were trying to do, and we'll be happy to help.

Multiple parameters
Note that if a template has multiple parameters, you need to separate them with a comma in the templatedata, like so:

Similar parameters
When a template has multiple parameters, sometimes some of them can be of the same kind. In this case, you only need to provide full properties for the first one, and the others can "inherit" their properties from it.

Limitations and questions

 * Missing features — TemplateData is very much an example of tool that was made available with few features, in hope that users would help to guide development of features that they desired. If you'd like to request new features for TemplateData, please let us know.
 * Delays in showing in templates — After adding TemplateData to a template, the metadata should be visible immediately when the template is opened in VisualEditor. However, it is possible that it takes hours before the metadata show. You can force an update by making a null edit to the template page itself (not the documentation subpage). To perform a null edit, open the template page for editing, and save the page without making any change.
 * Current issues — A list of current bugs and feature requests is available in bugzilla.

Tools

 * w:fr:Utilisateur:Ltrlg/scripts/TemplateDataEditor.js — A user script that makes the process of adding TemplateData easier