Piwik.js: ability to register plugins to execute logic when a request is sent

[mattab]

As a developer, I want to register function callbacks in Piwik.js Javascript tracking client, so that I can enrich the tracking requests with custom data, or do other custom logic whenever a request would be sent to the Tracking API (pageview, ecommerce, site search, etc.)

For more information see the tests here: https://github.com/piwik/piwik/pull/336/files

[mattab]

Message in forum post:

As I can read from piwik.js code, I'm not doing anything special with a plugin, just regular Tracker plugin functionality - depending on interaction type (click, load, unload, log, ...) append interaction type specific custom data to request query string, e.g. interaction type itself. Plugins are called for every Tracker.getRequest (line: "request += executePluginMethod(pluginMethod);"winking smiley.

I'm registering plugin with regular _paq.push([function() ....
Referencing Piwik singleton from such a function (e.g. to call addPlugin) will not work, because _paq array elements are evaluated in Piwik constructor, before Piwik is made accessible.

Calling addPlugin after piwik.js has been loaded is too late - I need plugin registered at construction time, before any interaction event has been tracked.

Moving/adding addPlugin from Piwik to Tracker public API, and making Tracker's addPlugin one of applyFirst methods, did the trick for me. I'm working on a pull request (which leaves addPlugin on Piwik singleton, but adds one on Tracker too).

[mattab]

In 2df1f90: Merge pull request #336 from sslavic/tracker_addPlugin

[piwik-js] Added support for registering plugins in Tracker public API fixes #5393

[mattab]

In ff475e5: add comment to function refs #5393
refs #336