This commit introduces the `behaviorTransformer` API to safely override behaviors defined in Discourse.
Two new plugin APIs are introduced:
- `addBehaviorTransformerName` which allows plugins and theme-components to add a new valid transformer name if they want to provide overridable behaviors;
- `registerBehaviorTransformer` to register a transformer to override behaviors.
It also introduces the function `applyBehaviorTransformer` which can be imported from `discourse/lib/transformer`. This is used to mark a callback containing the desired behavior as overridable and applies the transformer logic.
How does it work?
## Marking a behavior as overridable:
To mark a behavior as overridable, in Discourse core, first the transformer name must be added to `app/assets/javascripts/discourse/app/lib/transformer/registry.js`. For plugins and theme-components, use the plugin API `addBehaviorTransformerName` instead.
Then, in your component or class, use the function `applyBehaviorTransformer` to mark the Behavior as overridable and handle the logic:
- example:
```js
...
@action
loadMore() {
applyBehaviorTransformer(
"discovery-topic-list-load-more",
() => {
this.documentTitle.updateContextCount(0);
return this.model
.loadMore()
.then(({ moreTopicsUrl, newTopics } = {}) => {
if (
newTopics &&
newTopics.length &&
this.bulkSelectHelper?.bulkSelectEnabled
) {
this.bulkSelectHelper.addTopics(newTopics);
}
if (moreTopicsUrl && $(window).height() >= $(document).height()) {
this.send("loadMore");
}
});
},
{ model: this.model }
);
},
...
```
## Overriding a behavior in plugins or themes
To override a behavior in plugins, themes, or TCs use the plugin API `registerBehaviorTransformer`:
- Example:
```js
withPluginApi("1.35.0", (api) => {
api.registerBehaviorTransformer("example-transformer", ({ context, next }) => {
console.log('we can introduce new behavior here instead', context);
next(); // call next to execute the expected behavior
});
});
```
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