The PR superseeds the existing deepMerge algorithm used to merge
settings of parent and child models with a new algorithm that allows
to specify the way each setting is merged or mixed-in.
This configuration of this algorithm uses a merge policy specification.
The `getMergePolicy()` helper of BaseModelClass can be used to ease
model merge configuration.
Next is presented the expected merge behaviour for each option.
NOTE: This applies to top-level settings properties
- Any
- `{replace: true}` (default): child replaces the value from parent
- assignin `null` on child setting deletes the inherited setting
- Arrays
- `{replace: false}`: unique elements of parent and child cumulate
- `{rank: true}` adds the model inheritance rank to array
elements of type Object {} as internal property `__rank`
- Object {}:
- `{replace: false}`: deep merges parent and child objects
- `{patch: true}`: child replaces inner properties from parent
The recommended merge policy is returned by getMergePolicy()
when calling the method with option `{configureModelMerge: true}`.
The legacy built-in merge policy is returned by `getMergePolicy()`
when avoiding option `configureModelMerge`.
NOTE: it also delivers ACLs ranking in addition to the legacy
behaviour as well as fixes for settings `description` and `relations`
`getMergePolicy()` can be customized using model's setting
`configureModelMerge` as follows:
```
{
// ..
options: {
configureModelMerge: {
// merge options
}
}
// ..
}
```
`getMergePolicy()` method can also be extended programmatically as
follows:
```
myModel.getMergePolicy = function(options) {
const origin = myModel.base.getMergePolicy(options);
return Object.assign({}, origin, {
// new/overriding options
});
};
```
Add datasource and model setting `normalizeUndefinedInQuery`
to determine how it will handle undefined values. Options:
- nullify : converts undefined to null
- throw : throw an error on undefined value
- ignore : strip the key where undefined value is found
The default operation is to strip the key.
Support both promise and callback styles in
ModelBaseClass.notifyObserversOf.
When there is no callback supplied, the method returns a promise that
is resolved (or rejected) with the result.