An infinite `rem`, `em` or `vw` length skips the px clamp and reaches React Native as `null`

Issue 指出了 parseLength 和失败的复现用例 src/__tests__/native/infinite-relative-length.test.tsx。阅读 px、rem、em 和 vw 长度的处理逻辑，然后运行 yarn jest src/__tests__/native/infinite-relative-length.test.tsx。当相对单位的用例产生有限的样式值，符合报告中 px 的行为时，即为完成。

Before submitting a new issue

• I tested using the latest version of the library, as the bug might be already fixed.
• I tested using a supported version of react native.
• I checked for possible duplicate issues, with possible answers.

Bug summary

parseLength's px branch clamps an infinite or overflowing length to a safe integer; the rem branch (length.value * inlineRem) and the em and vw descriptors do not. calc(infinity * 1rem) therefore reaches the style as Infinity, which a device bundle carries as null, where calc(infinity * 1px) gives the clamped length. Tailwind's rounded-full is calc(infinity * 1px), so the px form is the common one; a theme that scales it with rem meets this.

The px case passes; the others fail:

calc(infinity * 1px): {"borderRadius":9007199254740991}
calc(infinity * 1rem): {"borderRadius":null}
calc(infinity * 1em): {"borderRadius":null}
calc(infinity * 1vw): {"borderRadius":null}

Library version

main at 2421ea7 (0.0.0-nightly.2421ea7)

Environment info

System:
  OS: Windows 11 10.0.26300
  CPU: "(32) x64 AMD Ryzen 9 9950X3D 16-Core Processor          "
  Memory: 155.26 GB / 255.67 GB
Binaries:
  Node:
    version: 26.12.1
    path: C:\Program Files\nodejs\node.EXE
  Yarn:
    version: 4.9.2
    path: C:\Users\<user>\AppData\Roaming\npm\yarn.CMD
  npm:
    version: 12.2.1
    path: C:\Program Files\nodejs\npm.CMD
  Watchman: Not Found
SDKs:
  Android SDK:
    API Levels:
      - "33"
      - "35"
      - "35"
      - "35"
      - "36"
      - "37"
    Build Tools:
      - 35.0.0
      - 36.0.0
      - 36.1.0
      - 37.0.0
    System Images:
      - android-26 | Google APIs Intel x86_64 Atom
      - android-28 | Google APIs Intel x86_64 Atom
      - android-29 | Google APIs Intel x86_64 Atom
      - android-30 | Google APIs Intel x86_64 Atom
      - android-31 | Google APIs Intel x86_64 Atom
      - android-32 | Google APIs Intel x86_64 Atom
      - android-33 | Google APIs Intel x86_64 Atom
      - android-34 | Google APIs Intel x86_64 Atom
      - android-35 | Google APIs Intel x86_64 Atom
      - android-36.1 | Google Play Intel x86_64 Atom
      - android-36.1 | Pre-Release 16 KB Page Size Google Play Intel x86_64 Atom
      - android-37.0 | Google APIs Intel x86_64 Atom
    Android NDK: Not Found
  Windows SDK: Not Found
IDEs:
  Android Studio: AI-262.9437.185.2621.16467767
  Visual Studio: Not Found
Languages:
  Java:
    version: 17.0.20.1
    path: C:\Program Files\Microsoft\jdk-17.0.20.101-hotspot\bin\javac.EXE
  Ruby: Not Found
npmPackages:
  "@react-native-community/cli": Not Found
  react:
    installed: 19.2.3
    wanted: 19.2.3
  react-native:
    installed: 0.86.3
    wanted: 0.86.3
  react-native-windows: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: Not found
  newArchEnabled: Not found
iOS:
  hermesEnabled: Not found
  newArchEnabled: Not found

Steps to reproduce

1. Clone the reproducer branch, which is main at 2421ea7 with one file added, src/__tests__/native/infinite-relative-length.test.tsx, and install:

   git clone --branch repro/537-relative-lengths-skip-the-px-clamp https://github.com/YevheniiKotyrlo/react-native-css
   cd react-native-css
   yarn install
   

2. Run yarn jest src/__tests__/native/infinite-relative-length.test.tsx.

src/__tests__/native/infinite-relative-length.test.tsx:

import { render, screen } from "@testing-library/react-native";
import { View } from "react-native-css/components/View";
import { registerCSS, testID } from "react-native-css/jest";

test.each(["1px", "1rem", "1em", "1vw"])(
  "border-radius: var(--r) over an inlined --r: calc(infinity * %s) is a finite length",
  (unit) => {
    registerCSS(`.a { --r: calc(infinity * ${unit}); border-radius: var(--r); }`);
    render(<View testID={testID} className="a" />);
    const { style } = screen.getByTestId(testID).props;
    console.log(`calc(infinity * ${unit}): ${JSON.stringify(style)}`);
    expect(Number.isFinite(style?.borderRadius)).toBe(true);
  },
);

Expected: an infinite rem, em or vw length is clamped, as an infinite px length is.

Actual: it reaches the style as Infinity, which a device bundle carries as null.

  console.log
    calc(infinity * 1px): {"borderRadius":9007199254740991}
      at log (src/__tests__/native/infinite-relative-length.test.tsx:11:13)
  console.log
    calc(infinity * 1rem): {"borderRadius":null}
      at log (src/__tests__/native/infinite-relative-length.test.tsx:11:13)
  console.log
    calc(infinity * 1em): {"borderRadius":null}
      at log (src/__tests__/native/infinite-relative-length.test.tsx:11:13)
  console.log
    calc(infinity * 1vw): {"borderRadius":null}
      at log (src/__tests__/native/infinite-relative-length.test.tsx:11:13)
FAIL src/__tests__/native/infinite-relative-length.test.tsx
  √ border-radius: var(--r) over an inlined --r: calc(infinity * 1px) is a finite length (26 ms)
  × border-radius: var(--r) over an inlined --r: calc(infinity * 1rem) is a finite length (6 ms)
  × border-radius: var(--r) over an inlined --r: calc(infinity * 1em) is a finite length (2 ms)
  × border-radius: var(--r) over an inlined --r: calc(infinity * 1vw) is a finite length (2 ms)
  ● border-radius: var(--r) over an inlined --r: calc(infinity * 1rem) is a finite length
    expect(received).toBe(expected) // Object.is equality
    Expected: true
    Received: false
      10 |     const { style } = screen.getByTestId(testID).props;
      11 |     console.log(`calc(infinity * ${unit}): ${JSON.stringify(style)}`);
    > 12 |     expect(Number.isFinite(style?.borderRadius)).toBe(true);
         |                                                  ^
      13 |   },
      14 | );
      15 |
      at toBe (src/__tests__/native/infinite-relative-length.test.tsx:12:50)
  ● border-radius: var(--r) over an inlined --r: calc(infinity * 1em) is a finite length
    expect(received).toBe(expected) // Object.is equality
    Expected: true
    Received: false
      10 |     const { style } = screen.getByTestId(testID).props;
      11 |     console.log(`calc(infinity * ${unit}): ${JSON.stringify(style)}`);
    > 12 |     expect(Number.isFinite(style?.borderRadius)).toBe(true);
         |                                                  ^
      13 |   },
      14 | );
      15 |
      at toBe (src/__tests__/native/infinite-relative-length.test.tsx:12:50)
  ● border-radius: var(--r) over an inlined --r: calc(infinity * 1vw) is a finite length
    expect(received).toBe(expected) // Object.is equality
    Expected: true
    Received: false
      10 |     const { style } = screen.getByTestId(testID).props;
      11 |     console.log(`calc(infinity * ${unit}): ${JSON.stringify(style)}`);
    > 12 |     expect(Number.isFinite(style?.borderRadius)).toBe(true);
         |                                                  ^
      13 |   },
      14 | );
      15 |
      at toBe (src/__tests__/native/infinite-relative-length.test.tsx:12:50)
Test Suites: 1 failed, 1 total
Tests:       3 failed, 1 passed, 4 total
Snapshots:   0 total
Time:        1.094 s, estimated 2 s
Ran all test suites matching /src\\__tests__\\native\\infinite-relative-length.test.tsx/i.

Reproducible example repository

https://github.com/YevheniiKotyrlo/react-native-css/tree/repro/537-relative-lengths-skip-the-px-clamp