Feature/prioritised eventifier

[oatymart]

Related to: https://oat-sa.atlassian.net/browse/PISA25-621

In a customer test runner plugin, we found a situation where 2 runner.before('move') handlers, attached to the runner by 2 distinct plugins, needed to be executed in a guaranteed order. [discussed here]

The proposed solution is to turn eventifier's handler array into a kind of priority queue - in the most simple way possible (instead of always Array.push, it uses Array.splice).

Use eventifier like so, and you can guarantee the order of handler execution:

function earlierHandler(e) { console.log(1, e); }
function laterHandler(e) { console.log(2, e); }
earlierHandler.priority = 7;
laterHandler.priority = 3;
emitter.on('hello', laterHandler); // attached 1st, called 2nd
emitter.on('hello', earlierHandler); // attached 2nd, called 1st
emitter.trigger('hello', 'world');

Use it without priority and it behaves as before (Array.splice behaves like Array.push).

To test: npm run test

[github-actions]

Version

Target Version	3.1.0
Last version	3.0.0

There are 0 BREAKING CHANGE, 1 feature, 0 fix

[olga-kulish]

Thanks! I think this is useful. It also doesn't do any harm: don't need it - don't use it.

But let's go forward with existing solution for customer ticket, because this requires more changes.

[olga-kulish]

This is not enough, because triggerBefore/triggerHandlers still executes all handlers in parallel (Promise.all(pHandlers)).

But it should do Promise.all only for handlers of the same priority, and also not execute next-priority if higher-priority cancelled this event.

As for who sets priority, I think we can start from hardcoding it in customer plugin, but logically test-runner should manage that, maybe by updating config option (+ inside some dynamicModulesIndex util to allow customer repo override).

---- test-runner qti.js install/init
<checks which plugins are enabled>
config.options.plugin1.beforeMoveHandlerPriority = 0;
config.options.plugin2.beforeMoveHandlerPriority = 1;

---- plugin-1
handler.priority = config.options.plugin1.beforeMoveHandlerPriority || 0
.before('move', handler)

---- plugin-2
handler.priority = config.options.plugin2.beforeMoveHandlerPriority || 0
.before('move', handler)