CPLAT-8036 Add useContext Hook

[joebingham-wk]

Motivation

Expose the useContext hook so that functional components can tap into it.

Changes

• Add useContext function
• Add an example
• Add tests

Testing

• Verify the example works as expected

Please Review @greglittlefield-wf @kealjones-wk @aaronlademann-wf @sydneyjodon-wk

[aaronlademann-wf]

It bothers me a bit that context will be dynamic unless you provide a type on the left side, and even then - there'd be no way to ensure that the type doesn't mismatch with the underlying type that was returned by createContext. Makes me wonder what the point of the generic parameter is on createContext.

By making these changes locally... all the typing seems to line up and makes context correctly inferred as a Map in this situation as a result of createContext<Map> being called on line 63.

// context.dart

- class Context {
+ class Context<T> {
// ...
}

- Context createContext<TValue>([
+ Context<TValue> createContext<TValue>([
// ...

// hooks.dart

- dynamic useContext(Context context) => // ...
+ T useContext<T>(Context<T> context) => // ...

@greglittlefield-wf @kealjones-wk @joebingham-wk is there some reason that I forgot about that led us to omit generic typing from the Context class?

[kealjones-wk]

Honestly I don't recall, I feel like there would have been a reason because the Context object in OverReact is typed exactly like that and i don't know why i would have omitted it in React-Dart unless it was just a minor oversight (very likely). @joebingham-wk if you can add this typing id say do it, but test the local context examples in browser and test it with over_react (tests & real examples if already in place) to make sure it doesn't break anything (i don't think it should).

[aaronlademann-wf]

+1

[greglittlefield-wf]

+10