This change adds a new "react-dom/unstable_testing" entry point but I believe its contents will exactly match "react-dom/index" for the stable build. (The experimental build will have the added new selector APIs.)
This commit builds on PR #22260 and makes the following changes:
* Adds a DevTools feature flag for named hooks support. (This allows us to disable it entirely for a build via feature flag.)
* Adds a new Suspense cache for dynamically imported modules. (This allows a component to suspend while importing an external code chunk– like the hook names parsing code).
* DevTools supports a hookNamesModuleLoaderFunction param to import the hook names module. I wish this could be handles as part of the react-devtools-shared package, but I'm not sure how to configure Webpack (4) to serve the chunk from react-devtools-inline. This seemed like a reasonable workaround.
The PR also contains an additional unrelated change:
* Removes pre-fetch optimization (added in DevTools: Improve named hooks network caching #22198). This optimization was mostly only important for cases where sources needed to be re-downloaded, something which we can now avoid in most cases¹ thanks to using cached responses already loaded by the page. (I tested this locally on Facebook and this change has no negative performance impact. There is still some overhead from serializing the JS through the Bridge but that's constant between the two approaches.)
¹ The case where we don't benefit from cached responses is when DevTools are opened after the page has already loaded certain scripts. This seems uncommon enough that I don't think it justified the added complexity of prefetching.
React currently suppress console logs in StrictMode during double rendering. However, this causes a lot of confusion. This PR moves the console suppression logic from React into React Devtools. Now by default, we no longer suppress console logs. Instead, we gray out the logs in console during double render. We also add a setting in React Devtools to allow developers to hide console logs during double render if they choose.
DevTools isn't being downloaded like typical JavaScript, so bundle size concerns don't apply. Parsing is still a consideration (so I'm open for discussion here) but I think this change would provide a couple of benefits:
* People are more likely to *actually read* non-minified source code when e.g. a breakpoint is hit (as with the recent debugger statement)
* Component stacks will be easier to parse on bug reports
This commit adds a new tab to the Settings modal: Debugging
This new tab has the append component stacks feature and a new one: break on warn
This new feature adds a debugger statement into the console override
* DevTools console override handles new component stack format
DevTools does not attempt to mimic the default browser console format for its component stacks but it does properly detect the new format for Chrome, Firefox, and Safari.
