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Andrew Scott
744e20641a
In some situations, calling `markForCheck` can result in an infinite
loop in seemingly valid scenarios. When a transplanted view is inserted
before its declaration, it gets refreshed in the retry loop of
`detectChanges`. At this point, the `Dirty` flag has been cleared from
all parents. Calling `markForCheck` marks the insertion tree up to the
root `Dirty`. If the declaration is checked again as a result (i.e.
because it has default change detection) and is reachable because its
parent was marked `Dirty`, this can cause an infinite loop. The
declaration is refreshed again, so the insertion is marked for refresh
(again). We enter an infinite loop if the insertion tree always calls
`markForCheck` for some reason (i.e. `{{createReplayObservable() | async}}`).
While the case above does fall into an infinite loop, it also truly is a
problem in the application. While it's not an infinite synchronous loop,
the declaration and insertion are infinitely dirty and will be refreshed
on every change detection round.
Usually `markForCheck` does not have this problem because the `Dirty`
flag is not cleared until the very end of change detection. However, if
the view did not already have the `Dirty` flag set, it is never cleared
because we never entered view refresh. One solution to this problem
could be to clear the `Dirty` flag even after skipping view refresh but
traversing to children.
PR Close #54329