This commit adds an ngTemplateGuard_ngIf static method to the NgIf
directive and an ngTemplateContextGuard static method to NgFor. The
function of these two static methods is to enable type narrowing
within generated type checking code for consumers of the directives.
PR Close#26203
Allows a directive to use the expression passed directly to a property
as a guard instead of filtering the type through a type expression.
This more accurately matches the intent of the ngIf usage of its template
enabling better type inference.
Moved NgIf to using this type of guard instead of a function guard.
Closes: #20967
Structural directives can now specify a type guard that describes
what types can be inferred for an input expression inside the
directive's template.
NgIf was modified to declare an input guard on ngIf.
After this change, `fullTemplateTypeCheck` will infer that
usage of `ngIf` expression inside it's template is truthy.
For example, if a component has a property `person?: Person`
and a template of `<div *ngIf="person"> {{person.name}} </div>`
the compiler will no longer report that `person` might be null or
undefined.
The template compiler will generate code similar to,
```
if (NgIf.ngIfTypeGuard(instance.person)) {
instance.person.name
}
```
to validate the template's use of the interpolation expression.
Calling the type guard in this fashion allows TypeScript to infer
that `person` is non-null.
Fixes: #19756?
PR Close#20702
BREAKING CHANGE: the compiler option `enableLegacyTemplate` is now disabled by default as the `<template>` element has been deprecated since v4. Use `<ng-template>` instead. The option `enableLegacyTemplate` and the `<template>` element will both be removed in Angular v6.
PR Close#18756
Only one h1 is allowed per document, and this is provided by the template.
So we cannot have any h1 tags (or `#` markdown shorthand) in any API docs.
Closes#16193
* feat(common): support `as` syntax in template/* bindings
Closes#15020
Showing the new and the equivalent old syntax.
- `*ngIf="exp as var1”`
=> `*ngIf="exp; let var1 = ngIf”`
- `*ngFor="var item of itemsStream |async as items”`
=> `*ngFor="var item of itemsStream |async; let items = ngForOf”`
* feat(common): convert ngIf to use `*ngIf="exp as local“` syntax
* feat(common): convert ngForOf to use `*ngFor=“let i of exp as local“` syntax
* feat(common): expose NgForOfContext and NgIfContext
Pete Bacon Darwin
Alex Rickabaugh
swseverance
Victor Berchet
Trotyl
Chuck Jazdzewski
Olivier Combe
Miško Hevery
Jason Aden