Implement Model Identity Keys #345
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also add comment about why we inject extra validation in debug mode
all makes event handler targets deterministic based on keys and child indices
At the moment, whenever a particular branch of a layout is updated, all the state (i.e. hooks and event handlers) that live within that branch are thrown away and reconstructed. Given IDOM’s current implementation for Layout this is unavoidable. To resolve this issue, we need to add a concept of “keys” which can be used to indicate the identity of an element within the layout structure. For example, if you have a list of elements that get re-ordered when a button is pressed, their state should be preserved, and reassigned to their new location in the layout. By default React requires keys to be used to communicate element identity whenever the order or number of simbling elements can change. While there are clear performance benefits for adhering to this stipulation, it’s often confusing for new developers. React has the further advantage of the JSX syntax, which makes it easier for the program to determine exactly when keys must be supplied by the user. To make the experience for new users simpler, and due to a lack of inforcement via JSX, IDOM will be to assume that any element without a key is new. Thus, for IDOM, keys will primarilly be a tool for optimization rather than a functional requirement.
this needs to be cleaned up now that we know what the bugs were
also fixes mypy typing issues
we can change this in a later pull request
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closes: #330
See the React docs for more info on this type of feature: https://reactjs.org/docs/lists-and-keys.html
This will allow the layout to know whether or not the identity of any particular model has changed, and thus, whether or not its state should be replaced.