The Store should never throw an Error without also emitting an event. Otherwise Store errors will be invisible to users, but the downstream errors they cause will be reported as bugs. (For example, github.com/facebook/react/issues/21402)
Emitting an error event allows the ErrorBoundary to show the original error.
Throwing is still valuable for local development and for unit testing the Store itself.
Add an explicit Bridge protocol version to the frontend and backend components as well as a check during initialization to ensure that both are compatible. If not, the frontend will display either upgrade or downgrade instructions.
Note that only the `react-devtools-core` (React Native) and `react-devtools-inline` (Code Sandbox) packages implement this check. Browser extensions inject their own backend and so the check is unnecessary. (Arguably the `react-devtools-inline` check is also unlikely to be necessary _but_ has been added as an extra guard for use cases such as Replay.io.)
DevTools was built with a fork of an early idea for how Suspense cache might work. This idea is incompatible with newer APIs like `useTransition` which unfortunately prevented me from making certain UX improvements. This PR swaps out the primary usage of this cache (there are a few) in favor of the newer `unstable_getCacheForType` and `unstable_useCacheRefresh` APIs. We can go back and update the others in follow up PRs.
### Messaging changes
I've refactored the way the frontend loads component props/state/etc to hopefully make it better match the Suspense+cache model. Doing this gave up some of the small optimizations I'd added but hopefully the actual performance impact of that is minor and the overall ergonomic improvements of working with the cache API make this worth it.
The backend no longer remembers inspected paths. Instead, the frontend sends them every time and the backend sends a response with those paths. I've also added a new "force" parameter that the frontend can use to tell the backend to send a response even if the component hasn't rendered since the last time it asked. (This is used to get data for newly inspected paths.)
_Initial inspection..._
```
front | | back
| -- "inspect" (id:1, paths:[], force:true) ---------> |
| <------------------------ "inspected" (full-data) -- |
```
_1 second passes with no updates..._
```
| -- "inspect" (id:1, paths:[], force:false) --------> |
| <------------------------ "inspected" (no-change) -- |
```
_User clicks to expand a path, aka hydrate..._
```
| -- "inspect" (id:1, paths:['foo'], force:true) ----> |
| <------------------------ "inspected" (full-data) -- |
```
_1 second passes during which there is an update..._
```
| -- "inspect" (id:1, paths:['foo'], force:false) ---> |
| <----------------- "inspectedElement" (full-data) -- |
```
### Clear errors/warnings transition
Previously this meant there would be a delay after clicking the "clear" button. The UX after this change is much improved.
### Hydrating paths transition
I also added a transition to hydration (expanding "dehyrated" paths).
### Better error boundaries
I also added a lower-level error boundary in case the new suspense operation ever failed. It provides a better "retry" mechanism (select a new element) so DevTools doesn't become entirely useful. Here I'm intentionally causing an error every time I select an element.
### Improved snapshot tests
I also migrated several of the existing snapshot tests to use inline snapshots and added a new serializer for dehydrated props. Inline snapshots are easier to verify and maintain and the new serializer means dehydrated props will be formatted in a way that makes sense rather than being empty (in external snapshots) or super verbose (default inline snapshot format).
* Enable prefer-const rule
Stylistically I don't like this but Closure Compiler takes advantage of
this information.
* Auto-fix lints
* Manually fix the remaining callsites
DevTools previously used the NPM events package for dispatching events. This package has an unfortunate flaw though- if a listener throws during event dispatch, no subsequent listeners are called. I've replaced that event dispatcher with my own implementation that ensures all listeners are called before it re-throws an error.
This commit replaces that event emitter with a custom implementation that calls all listeners before re-throwing an error.
