We use a `<DataSource @src={{url}} />` component throughout our UI for when we want to load data from within our components. The URL specified as the `@src` is used to map/lookup what is used in to retrieve data, for example we mostly use our repository methods wrapped with our Promise backed `EventSource` implementation, but DataSource URLs can also be mapped to EventTarget backed `EventSource`s and native `EventSource`s or `WebSockets` if we ever need to use those (for example these are options for potential streaming support with the Consul backend).
The URL to function/method mapping previous to this PR used a very naive humongous `switch` statement which was a temporary 'this is fine for the moment' solution, although we'd always wanted to replace with something more manageable.
Here we add `wayfarer` as a dependency - a very small (1kb), very fast, radix trie based router, and use that to perform the URL to function/method mapping.
This essentially turns every `DataSource` into a very small SPA - change its URL and the view of data changes. When the data itself changes, either the yielded view of data changes or the `onchange` event is fired with the changed data, making the externally sourced view of data completely reactive.
```javascript
// use the new decorator a service somewhere to annotate/decorate
// a method with the URL that can be used to access this method
@dataSource('/:ns/:dc/services')
async findAllByDatacenter(params) {
// get the data
}
// can use with JS in a route somewhere
async model() {
return this.data.source(uri => uri`/${nspace}/${dc}/services`)
}
```
```hbs
{{!-- or just straight in a template using the component --}}
<DataSource @src="/default/dc1/services" @onchange="" />
```
This also uses a new `container` Service to automatically execute/import certain services yet not execute them. This new service also provides a lookup that supports both standard ember DI lookup plus Class based lookup or these specific services. Lastly we also provide another debug function called DataSourceRoutes() which can be called from console which gives you a list of URLs and their mappings.
There are many places in the API where we receive a property set to
`null` which can then lead to defensive code deeper in the app in order
to guard for this type of thing when usually we are expecting an array
or for the property to be undefined using omitempty on the backend.
Previously we had two places where we would deal with this in the
serializer using our 'remove-null' util (KV and Intentions).
This new decorator lets you declaritively define this type of data using
a decorator @NullValue([]) (which would replce a null value with [].
@NullValue in turn uses a more generic @replace helper, which we
currently don't need but would let you replace any value with another,
not just a null value.
An additional benefit here is that the guard/replacement is executed
lazily when we get the property instead of serializing all the values
when they come in via the API. On super large datasets, where we only
visualize part of the dataset (say in our scroll panes), this feels like
a good improvement on the previous approach.
John Cowen