Leo Camus
ccea5fd23e
## Summary
V8 prefixes async call sites with `async ` when it prints a stack, like
this:
```
Error: boom
at inner (/tmp/asy.js:1:44)
at async outerName (/tmp/asy.js:2:30)
```
`parseStackTraceFromChromeStack` captures `async outerName` as the frame
name and strips the prefix here:
```js
} else if (name.startsWith('async ')) {
name = name.slice(5);
isAsync = true;
}
```
`'async '` is six characters, so `slice(5)` leaves the space behind and
the frame name comes back as `' outerName'` rather than `'outerName'`.
I noticed it while reading the parser, and it is not purely cosmetic:
that name is the first element of the `ReactFunctionLocation` returned
by `extractLocationFromComponentStack` and
`extractLocationFromOwnerStack`, which `backend/fiber/renderer.js`
stores as `instance.source`. Any async component whose frame reaches
that path is recorded under a name with a stray leading space.
The same line exists in
`packages/react-server/src/ReactFlightStackConfigV8.js`, which the
DevTools file is a copy of. After review I fixed it in this PR as well,
in a second commit. There it only matters on the fallback path that
parses an already formatted stack string, when the error's `stack` was
read or assigned before React reaches it. #37130 is open on that file
too, but it does not touch these lines.
## How did you test this change?
I first confirmed the format V8 actually emits, rather than assuming it:
```
$ node -e 'async function inner(){await null;throw new Error("boom")}
async function outerName(){await inner()}
outerName().catch(e=>console.log(e.stack))'
Error: boom
at inner ([eval]:1:52)
at async outerName ([eval]:2:33)
```
Then I added a case to the existing `extractLocationFromComponentStack`
block in `utils-test.js`. Against `main` it fails with exactly the
leading space:
```
● utils › extractLocationFromComponentStack › should strip the async prefix from a frame name
- Expected - 1
+ Received + 1
Array [
- "Comments",
+ " Comments",
"https://react.dev/_next/static/chunks/848-122f91e9565d9ffa.js",
5,
9236,
]
```
With the one-character fix applied:
```
$ yarn test --build --project=devtools -r=experimental utils-test
PASS packages/react-devtools-shared/src/__tests__/utils-test.js
Tests: 63 passed, 63 total
```
I also ran the whole DevTools project before and after to check I was
not moving anything else. Both runs end at `9 failed, 4 failed suites`,
the same test names each time (`componentStacks`, `console`,
`inspectedElement`, `legacy/inspectElement`), so those failures are
pre-existing on `main` in my environment and unrelated to this change.
The only difference between the two runs is my new test: 586 passed
before, 587 after.
For the Flight side I added `ReactFlightStackConfigV8-test.js`, which
assigns a formatted stack to an error and checks what `parseStackTrace`
returns. Against `main` it fails with the same leading space (`"
outerName"`); with the fix it passes on stable and experimental in
development. It is gated to `__DEV__` because that fallback goes through
the DEV-only stack cache. `ReactFlightServer-test` and
`ReactFlightAsyncDebugInfo-test` still pass next to it (23 tests).
`prettier` and `eslint` are clean on all changed files. `yarn flow
dom-node` reported no errors for the DevTools commit; I did not rerun
Flow after the one-character Flight change.
AI tools used
React · 
React is a JavaScript library for building user interfaces.
- Declarative: React makes it painless to create interactive UIs. Design simple views for each state in your application, and React will efficiently update and render just the right components when your data changes. Declarative views make your code more predictable, simpler to understand, and easier to debug.
- Component-Based: Build encapsulated components that manage their own state, then compose them to make complex UIs. Since component logic is written in JavaScript instead of templates, you can easily pass rich data through your app and keep the state out of the DOM.
- Learn Once, Write Anywhere: We don't make assumptions about the rest of your technology stack, so you can develop new features in React without rewriting existing code. React can also render on the server using Node and power mobile apps using React Native.
Learn how to use React in your project.
Installation
React has been designed for gradual adoption from the start, and you can use as little or as much React as you need:
- Use Quick Start to get a taste of React.
- Add React to an Existing Project to use as little or as much React as you need.
- Create a New React App if you're looking for a powerful JavaScript toolchain.
Documentation
You can find the React documentation on the website.
Check out the Getting Started page for a quick overview.
The documentation is divided into several sections:
- Quick Start
- Tutorial
- Thinking in React
- Installation
- Describing the UI
- Adding Interactivity
- Managing State
- Advanced Guides
- API Reference
- Where to Get Support
- Contributing Guide
You can improve it by sending pull requests to this repository.
Examples
We have several examples on the website. Here is the first one to get you started:
import { createRoot } from 'react-dom/client';
function HelloMessage({ name }) {
return <div>Hello {name}</div>;
}
const root = createRoot(document.getElementById('container'));
root.render(<HelloMessage name="Taylor" />);
This example will render "Hello Taylor" into a container on the page.
You'll notice that we used an HTML-like syntax; we call it JSX. JSX is not required to use React, but it makes code more readable, and writing it feels like writing HTML.
Contributing
The main purpose of this repository is to continue evolving React core, making it faster and easier to use. Development of React happens in the open on GitHub, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving React.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our contributing guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React.
Good First Issues
To help you get your feet wet and get you familiar with our contribution process, we have a list of good first issues that contain bugs that have a relatively limited scope. This is a great place to get started.
License
React is MIT licensed.