The content projection mechanism is static, in that it only looks at the static
template nodes before directives are matched and change detection is run.
When you have a selector-based content projection the selection is based
on nodes that are available in the template.
For example:
```
<ng-content selector="[some-attr]"></ng-content>
```
would match
```
<div some-attr="..."></div>
```
If you have an inline-template in your projected nodes. For example:
```
<div *ngIf="..." some-attr="..."></div>
```
This gets pre-parsed and converted to a canonical form.
For example:
```
<ng-template [ngIf]="...">
<div some-attr=".."></div>
</ng-template>
```
Note that only structural attributes (e.g. `*ngIf`) stay with the `<ng-template>`
node. The other attributes move to the contained element inside the template.
When this happens in ivy, the ng-template content is removed
from the component template function and is compiled into its own
template function. But this means that the information about the
attributes that were on the content are lost and the projection
selection mechanism is unable to match the original
`<div *ngIf="..." some-attr>`.
This commit adds support for this in ivy. Attributes are separated into three
groups (Bindings, Templates and "other"). For inline-templates the Bindings
and "other" types are hoisted back from the contained node to the `template()`
instruction, so that they can be used in content projection matching.
PR Close#29041
Previously, there could be identical template/listener function names
for a component's template, if it had multiple similarly structured
nested sub-templates or listeners.
This resulted in build errors:
`Identifier '<SOME_IDENTIFIER>' has already been declared`
This commit fixes this by ensuring that the template index is included
in the `contextName` passed to the `TemplateDefinitionBuilder`
responsible for processing nested sub-templates.
Similarly, the template or element index is included in the listener
names.
PR Close#27766
Prior to this change, we were unable to match directives using `ng-template` tags (for example the following selector would not work even though there might be some <ng-template>s in a template: `ng-template[directiveA]`. As a result, that broke some components that relies on such selectors to work. In order to resolve the problem, we now pass tag name to the `template` instruction (where we passed `null` before) and this tag name is used for matching at runtime. This update should also help support projecting containers, because the tag name is required to properly match such elements.
PR Close#27636
Pete Bacon Darwin
George Kalpakas
Matias Niemelä
Andrew Kushnir
Olivier Combe
Marc Laval
Pawel Kozlowski