This commit introduces the `valueTransformer`API to safely override values defined in Discourse.
Two new plugin APIs are introduced:
- `addValueTransformerName` which allows plugins and theme-components to add a new valid transformer name if they want to provide overridable values;
- `registerValueTransformer` to register a transformer to override values.
It also introduces the function `applyValueTransformer` which can be imported from `discourse/lib/transformer`. This function marks the desired value as overridable and applies the transformer logic.
How does it work?
## Marking a value as overridable:
To mark a value 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 `addValueTransformerName` instead.
Then, in your component or class, use the function `applyValueTransformer` to mark the value as overridable and handle the logic:
- example:
```js
export default class HomeLogo extends Component {
@service session;
@service site;
...
get href() {
return applyValueTransformer("home-logo-href", getURL("/"));
}
```
## Overriding a value in plugins or themes
To override a value in plugins, themes, or TCs use the plugin API `registerValueTransformer`:
- Example:
```js
withPluginApi("1.34.0", (api) => {
api.registerValueTransformer("example-transformer", ({ value }) => {
return "new-value";
});
});
```
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