Previous to this change, we assumed embedded views could only be created after
their parent template node had completed processing. As a result, we only set
up query logic for containers after directives on the node were created.
However, this assumption didn't take into account the case where a directive
on a template node could create views in its constructor.
This commit fixes query logic to work with views created in constructors.
In that case, we need to create a query container before the new view is
rendered so query results in the view aren't lost. But since the query container
is created before directives have completed processing, we also have to ensure
that query results gathered later on the template node are inserted before that
query container. Otherwise, query results in embedded views will clobber query
results on template nodes.
This splice mode may be slightly slower than the normal matching for queries on
containers, but we should only fall back to this strategy in the edge case where
views are created in constructors. (We should encourage developers to create
views in ngOnInit instead).
PR Close#29983
This PR tackles a simple case where ViewRef definition point (<ng-template>) is the
same as the insertion point (ViewContainerRef requested on the said <ng-template>).
For this particular case we can assume that we know a container into which a given
view will be inserted when a view is created. This is not true fall all the possible
cases so follow-up PR will be needed to extend this basic implementation.
PR Close#24179
To prepare for pending ngForOf work, the dep from instructions -> query
should be broken. This will enable a dep from di -> instructions while
avoiding a di -> instructions -> query -> di cycle.
Analyzing this cycle also uncovered another problem: the implementation
of query() breaks tree-shaking through a hard dependency on DI concepts
of TemplateRef, ElementRef, ViewContainerRef. This is fundamentally due
to how query() can query for those values without any configuration.
Instead, this fix introduces the concept by employing the strategy
pattern, and redefining QueryReadType to pass a function which will
return one of the above values. This strategy is then used for 'read'
instead of an enum in cases where special values should be read from
the DI system.
PR Close#21430
