angular/angular.js

@ngdoc error
@name $compile:reqslot
@fullName Required transclusion slot
@description

This error occurs when a directive or component try to transclude a slot that is not provided.

Transcluded elements must contain something. This error could happen when you try to transclude a self closing tag element.
Also you can make a transclusion slot optional with a `?` prefix.

```js
// In this example the <my-component> must have an <important-component> inside to transclude it.
// If not, a reqslot error will be generated.

var componentConfig = {
  template: 'path/to/template.html',
  transclude: {
    importantSlot: 'importantComponent', // mandatory transclusion
    optionalSlot: '?optionalComponent',  // optional transclusion
  }
};

angular
  .module('doc')
  .component('myComponent', componentConfig)

```

```html
<!-- Will not work because <important-component> is missing -->
<my-component>
</my-component>

<my-component>
  <optional-component></optional-component>
</my-component>

<!-- Will work -->
<my-component>
  <important-component></important-component>
</my-component>

<my-component>
  <optional-component></optional-component>
  <important-component></important-component>
</my-component>
```