The rationale of this change is to improve the inter-operability with web
components that might make use of the `<template>` tag.
DEPRECATION
The template tags and template attribute are deprecated:
<template ngFor [ngFor]=items let-item><li>...</li></template>
<li template="ngFor: let item of items">...</li>
should be rewritten as:
<ng-template ngFor [ngFor]=items let-item><li>...</li></ng-template>
Note that they still be supported in 4.x with a deprecartion warning in
development mode.
MIGRATION
- `template` tags (or elements with a `template` attribute) should be rewritten
as a `ng-template` tag,
- `ng-content` selectors should be updated to referto a `ng-template` where they
use to refer to a template: `<ng-content selector="template[attr]">` should be
rewritten as `<ng-content selector="ng-template[attr]">`
- if you consume a component relying on your templates being actual `template`
elements (that is they include a `<ng-content selector="template[attr]">`). You
should still migrate to `ng-template` and make use of `ngProjectAs` to override
the way `ng-content` sees the template:
`<ng-template projectAs="template[attr]">`
- while `template` elements are deprecated in 4.x they continue to work.
NgIf syntax has been extended to support else clause to display template
when the condition is false. In addition the condition value can now
be stored in local variable, for later reuse. This is especially useful
when used with the `async` pipe.
Example:
```
<div *ngIf="userObservable | async; else loading; let user">
Hello {{user.last}}, {{user.first}}!
</div>
<template #loading>Waiting...</template>
```
closes#13061closes#13297
Victor Berchet
Misko Hevery