Help:TemplateData/eml



What is TemplateData?
TemplateData is a way of storing information about a template and its parameters, so that the VisualEditor can retrieve and display it in 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 a 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.



Structure of TemplateData
TemplateData's structure is based around the JSON standard, and is fairly simple. Note that all descriptions in TemplateData must be in plain text (no wikitext, no links, etc.).

The first thing to do is to type out a pair of  tags, anywhere on the template's documentation subpage, like so:

This tells the software that everything between the two tags is TemplateData, and should be referenced when the template is used.



Example
The descriptions inside TemplateData follow a standard layout; let's say that you have a template called "Commons" for linking to a Commons category about a topic. It takes one mandatory parameter: the name of the category on Commons. The TemplateData would look something like this:

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.", "default": "Category:CommonsRoot", "type": "string", "required": true }       } }



Description and parameters
Once you're done, hit "save". If you've made errors, it will not let you save (which 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 will be happy to help.

Note that each bit of information is enclosed in quotation marks (except for  and  ), and separated from the next bit by a comma (unless it's the last one).



Parameter aliases
Some templates allow a same parameter to have different names.

For example,  could also be written as   or.

To add this information to TemplateData, you simply need to add the aliases to the parameter's information:



Multiple parameters
If you have multiple parameters, just repeat each section (starting from the "1" tag) and fill it out as you see fit. 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.



Blank boilerplate
You can copy the blank boilerplate below to add new TemplateData to a template. Only the most common tags are included.



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.



Strumèint

 * TemplateDataEditor — A user script that makes the process of adding TemplateData easier. It currently exists in French (contains English, Italian, Japanese and Korean translations), and can easily be translated into other languages.
 * TemplateData Wizard — A tool that generates TemplateData through an interactive interface.
 * Skeleton TemplateData generator — A tool that reads the source wikicode of a template, tries to find all the parameters used and outputs a skeleton document with the parameters listed.
 * JSONLint — A tool that allows you to validate manually-written JSON to help find errors in the syntax.