This is just a demo of how we can implement robust types for Ember's get and set functions (which could be used as a model for other libraries like lodash as well).

To see it in action, check out the ~4½-minute demo video—or, better, clone this repo and mess around with demo.ts!

This correctly handles a number of significant "edge cases" over the base example shown in the original PR adding this feature to TS and the blog post announcement:

• If any type in the path is null | undefined, this approach resolves the final type to include that correctly. For example, given an item foo: { bar?: string }, doing get(foo, 'bar.length') will have the type number | undefined, since bar may be undefined.

• Ember's classic ObjectProxy type is unwrapped correctly along the way. This means that places where you have to use get in Ember today (for example, async relationships on Ember Data models) can be correctly unwrapped by this implementation.

• Autocompletion works for the string keys as well. Given foo: { bar: { baz: string } }, typing get(foo, ' and triggering auto completion, manually or automatically, will show bar and bar.baz. (The only downside here is that it will also show all the properties on any given suggestion, e.g. bar.baz.length and bar.baz.indexOf and so on.)

Note: This is definitely only prototype code at the moment. There are no type tests, and there are many gaps, and the demos with ObjectProxy and similar here are just that: demos, which do not use the actual types from Ember. However, the demo does represent a good future direction, and proves that we can support at least the vast majority of use cases for Ember going forward.

There are still gaps here, too. For example, this.get does not complete correctly. (We can likely work around this in some way or another, but still be figured out.)