Plugin contribution checklist

Before approaching the Moodle plugins directory and submitting your plugin (or a new plugin version), you are encouraged to go through the checklists below and fix eventual issues with your plugin. Doing so will make the reviewer of your plugin happy :-) and may have impact on how long your plugin has to spend in the approval queue before it lands smoothly.

Meta-data

Plugin descriptions

Have a meaningful description of your plugin prepared in English.
You will need a short concise description (just a sentence or two) for the short description field, and another elaborated one for the full description field.
It is encouraged to have the same info at the plugin record page and in its README file.

Supported Moodle versions

New plugins submitted into the plugins directory must support at least one of the currently maintained Moodle version.
See Releases for the list of currently maintained Moodle versions (policy issue MDL-47579).

Code repository name

Provide a consistent experience for other Moodle developers and site administrators - follow the repository naming convention for Moodle plugins:
moodle-{plugintype}_{pluginname}.

Source control URL

Facilitate sharing and further development of your open-source plugin - provide publicly accessible URL of your code repository.
Github is a choice of most Moodle plugin developers.

Bug tracker URL

Encourage participation and have a place to report issues, bugs, make feature requests, or suggest other types of improvements.
Both Moodle tracker and Github issues are common.
See Plugin_contribution#Tracker if you want to use the Moodle tracker.

Documentation URL

Have a place where further documentation of your plugin will be located.
Moodle docs is preferred location, Github wikis or your own website will work, too.

Illustrative screenshots

Capture some screenshots of your plugin to help folks get an idea of what it looks like when installed.
We will use these screenshots at more places in the plugins directory in the future.

Licensing

All files that implement the interface between the Moodle core and the plugin must be licensed under GNU GPL v3 (or later).
Additional files contained in the plugin ZIP package (such as third party libraries used by the plugin, or included media) may eventually use other license as long as it is GPL compatible. See Plugin files#thirdpartylibs.xml for how to do it.
Note that binary files violate GPL unless the source code is also included or available (e.g. Java classes or Flash).

Subscription needed

If the plugin requires a third-party subscription based service, make sure the description states it very clearly.
To allow the testing of the plugin functionality, please provide us with demo credentials (such as API keys etc) so that the approval team can use them to see the plugin in action.

Usability

Installation

Make sure the plugin installs smoothly from the ZIP package using the in-build plugin installation interface.
If any non-standard post-installation steps are needed, make sure they are clearly listed in both plugin description and the README file.

Dependencies

If the plugin depends on another additional plugin, make sure it is clearly stated in the description and in the README file.
Also declare the dependency explicitly in the plugin's version.php file.

Functionality

Test the plugin functionality with full developer debugging enabled.
Make sure the code does not throw unexpected PHP warnings, notices or even errors.

Cross-DB compatibility

Test the plugin with multiple database engines supported by Moodle.
At very least, the plugin is supposed to work with MySQL and PostgreSQL unless reasons are clearly explained in the description and the README file (such as the plugin is a wrapper for third-party DB specific utility).
Data manipulation API helps you to ensure cross-db compatibility.

Coding

Coding style

It is encouraged to follow Moodle coding style and other coding guidelines.
It's not always possible to achieve "all greens" in automated syntax checks (especially when third party libraries are involved) but you should aim to it.
Consistent style helps others to read and understand your code (not only during the approval review).

English

Moodle is an international project. To facilitate sharing, reviews of and contributions to your code, all comments, variable names, function names etc. should be in English.

Boilerplate

All files should contain the common boilerplate at the beginning with explicit GPL license statement.
See the section Coding_style#Files for the template.

Copyrights

All files should contain the @copyright tag with your name.
If you are re-using someone else's file, keep the original copyrights reference to the previous author and add your name as a copyright holder.
Both things should be clear: (1) that it is you to be blamed for the file code and (2) that your work is based on someone else's work.

/**

* @copyright 2019 John Smith <john.smith@example.com>
* @copyright based on work by 2010 Mary Stuart <mary.stuart@example.com>
*/

CSS styles

Make sure to use properly namespaced selectors so that your style sheets can be safely concatenated with the ones provided by other plugins.
Plugin specific CSS selectors are needed to make sure that your styling does not accidentally affect other parts of Moodle outside your plugin scope.
For example, instead of the selector .contentarea it is better to use something like .path-mod-mymodule .contentarea as the .path-* classes are automatically added by the Moodle core renderers to the HTML <body> tag.

Namespace collisions

Check that all your DB tables, settings, functions, classes, constants and variables are named correctly. In most cases their names must start with the plugin type and plugin name, as in block_yourname_something (so called frankenstyle prefix). Modules are an exception to this rule as functions such as get_coursemodule_from_id() rely on there being no preface of 'mod'.
Do not define own classes, functions, variables or constants in the global PHP scope without the valid frankenstyle prefix.
See Coding style#Functions and Methods for details.

Settings storage

Check that your settings are stored in the table config_plugins and not in the main config table.
This helps to avoid $CFG bloat and potential collisions.
Use get_config() to pull the settings data out of the config_plugins table.
In the file settings.php, the setting names are supposed to be plugintype_pluginname/settingname (note the slash) and not plugintype_pluginname_settingname or even just settingname.
If you eventually need to change the settings yourself, use set_config().

Strings

Avoid hard-code texts in the code, always use get_string().
Just the English strings should ship with the plugin. All other translations are supposed to be submitted as contributions at https://lang.moodle.org once your plugin is approved - see Translating plugins.
Your code must not rely on trailing and leading whitespace in strings.
The string file must be considered as pure data file with the syntax $string['id'] = 'value';. No other PHP syntax such as concatenation, heredoc and nowdoc is supported by the tools that we use when processing your strings (even if it may work in Moodle itself).
The English language pack (lang/en/) in Moodle does not use "Capitalised Titles".

Privacy

Avoid gathering, storing, processing and sharing personal data unless they are needed for the plugin functionality.
Inform about all the personal data that the plugin processes, via both description and the Privacy API.

Security

Never trust the user input.
Do not access superglobals like $_REQUEST directly, use wrappers like required_param() with correct type declared to sanitize input.
Always use placeholders in custom SQL queries (? or :named).
Always check for the sesskey before taking an action on submitted data.
Check for require_login().
Always check that the user has appropriate capabilities before displaying the widgets and before taking the actual action.
Avoid using malicious functions like call_user_func(), eval(), unserialize() and so on, especially when they would be called with user-supplied data.

Documentation