[Compiler Bug]: Coverage report shows missing branch coverage

What kind of issue is this?

• React Compiler core (the JS output is incorrect, or your app works incorrectly after optimization)
• babel-plugin-react-compiler (build issue installing or using the Babel plugin)
• eslint-plugin-react-compiler (build issue installing or using the eslint plugin)
• react-compiler-healthcheck (build issue installing or using the healthcheck script)

Link to repro

https://github.com/ValentinGurkov/vitest-react-compiler-missing-coverage-repro

Repro steps

Describe the bug

Hello,

I've been testing out the new React compiler and have noticed that the code coverage report becomes incorrect with the compiler turned it. I believe it may be related to the way it changes the output react component code.

I've created a minimal reproduction repository to demonstrate the issue: 👉 https://github.com/ValentinGurkov/vitest-react-compiler-missing-coverage-repro, but I also want to share my findings here:

The button we are going to test is a simple one:

export const Button = () => {
    return <button>Click me</button>;
};

As well as its test:

import { page } from '@vitest/browser/context';
import { Button } from '@repo/components/ui/button.js';
import { describe, expect, it} from 'vitest';
import { render } from 'vitest-browser-react';

describe(Button, () => {
    it('renders with default variants', async () => {
        render(<Button />);

        const button = page.getByRole('button', { name: 'Click me' });

        await expect.element(button).toBeInTheDocument();
    });
});

The coverage report with the React compiler turned on looks like:

   ✓  browser (chromium)  test/components/ui/button.test.tsx (1 test) 9ms
   ✓ Button > renders with default variants 9ms

 Test Files  1 passed (1)
      Tests  1 passed (1)
   Start at  20:34:46
   Duration  632ms (transform 0ms, setup 133ms, collect 28ms, tests 9ms, environment 0ms, prepare 93ms)

 % Coverage report from v8
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