With this commit, the templates that are given while instantiating the
App class can be an object with templates not yet parsed (i.e. string,
not Document). This allow to instantiate the App class with templates
that are not yet parsed, and these templates will be parsed only when
needed.
Part of task-id 3601257
Before this commit, the App destroy method would not destroy everything
synchronously. The code scheduled a flush, which is asynchronous, to
finally clean up the task lists, and destroy the cancelled nodes. But
this is not really good for tests: we need a stronger guarantee that
nothing will happen after the destroy.
With this commit, we simply call the processTask method immediately
after destroying the root component, so all cancelled nodes will be
destroyed immediately.
Previously, refs could get set to null incorrectly, or could stay set
when they shouldn't. This was caused by the fact that singleRefSetter
and multiRefSetters are created on every render, meaning that any render
that did not affect the status of the ref (mounted or not), would
overwrite the previous ref setter, including its closure, causing the
captured `_el` or `count` to be lost. This means that on a subsequent
render that did affect the status of the ref, the singleRefSetter would
consider that it did not set the ref, and so shouldn't unset it, causing
it to incorrectly stay keep the element, while in multiRefSetter, the
opposite problem occured: the count would be 0 on removal, causing it to
believe that it was the first call in the corresponding patch that
affected the ref, when in fact, the closure is already stale, because it
was created from the previous render, and the fresh multiRefSetter from
the latest render may already have been called by an element with that
ref that came earlier in the template.
This commit changes the ref setting strategy to work around the issue of
stale closures: we define a setRef method on ComponentNode that is
always called, this method ignores calls with `null`, meaning that the
refs object on the ComponentNode never reverts to a null value for any
key. Instead, the useRef hook will check whether the element that the
ref points to is still mounted, and return null if not.
Previously, attempting to mount an app in an iframe would crash, saying
that the target is not a valid DOM element, this is because instanceof
checks do not work cross-frame as global objects do not have the same
identity in frames as with the main window. This commit fixes that by
making sure the target is an instance of HTMLElement of the
corresponding window, and checks that the corresponding document body
contains it.
Pierre Rousseau