A list item that cannot be read is dropped and the list shifts: `transition-property: var(--missing), height` gives `height` the first duration

Start with resolveValue in src/native/styles/resolve.ts, where the issue says array entries resolving to undefined are filtered out. Trace how that result reaches transition property and timing function readers, then check the supplied reproducer tests for both unresolved variables and unreadable list items. Done means each invalid list declaration is rejected as a whole in both inline and folded routes.

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

A list entry whose var() has no value is removed before the declaration is read, so the list shortens and every later entry moves off its index: transition-property: var(--missing), height; transition-duration: 1s, 2s renders transitionProperty: ["height"] beside [1000, 2000], and height takes 1s. CSS makes the whole declaration invalid at computed-value time (css-variables-1 §3), so transition-property computes to all. The folded and the kept routes render it alike.

{"transitionProperty":["height"],"transitionDuration":[1000,2000]}
{"transitionProperty":["height"],"transitionDuration":[1000,2000]}

Both fail. An item the compiler cannot read is dropped the same way: transition-timing-function: linear(0, 1), ease-in on opacity, width compiles to "ease-in", which Reanimated repeats for both properties, where the declaration should be dropped whole (unreadable-item.test.tsx in the gist):

.a { transition-property: opacity, width; transition-duration: 1s; transition-timing-function: linear(0, 1), ease-in; } -> d [{"transitionProperty":["opacity","width"],"transitionDuration":[1000],"transitionTimingFunction":"ease-in"}]; style {"transitionProperty":["opacity","width"],"transitionDuration":[1000],"transitionTimingFunction":"ease-in"}; warnings {"values":{"transition-timing-function":["linear()"]}}
.a { --e: ease-in; transition-property: opacity, width; transition-duration: 1s; transition-timing-function: linear(0, 1), var(--e); } -> d [{"transitionProperty":["opacity","width"],"transitionDuration":[1000]},[[{},"var","e",1],"transitionTimingFunction",1]]; style {"transitionProperty":["opacity","width"],"transitionDuration":[1000],"transitionTimingFunction":"ease-in"}; warnings {"values":{"transition-timing-function":["linear()"]}}

resolveValue (src/native/styles/resolve.ts) filters out an array entry that resolves to undefined and resolves the rest, so a declaration's reader never learns that an entry was invalid.

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 2 files added in src/__tests__/native, and install:

   git clone --branch repro/533-unresolved-variable-drops-out-of-a-list https://github.com/YevheniiKotyrlo/react-native-css
   cd react-native-css
   yarn install
   

2. Run yarn jest src/__tests__/native/unreadable-item.test.tsx src/__tests__/native/unresolved-variable-in-list.test.tsx.

src/__tests__/native/unreadable-item.test.tsx:

// Run from a react-native-css checkout: copy to src/__tests__/native/, then `yarn jest` it.
import { StyleSheet } from "react-native";

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

jest.mock("../../native/reanimated", () => ({
  animatedComponentFamily: (component: unknown) => component,
}));

test.each([
  [".a { transition-property: opacity, width; transition-duration: 1s; transition-timing-function: linear(0, 1), ease-in; }"],
  [".a { --e: ease-in; transition-property: opacity, width; transition-duration: 1s; transition-timing-function: linear(0, 1), var(--e); }"],
])("%s", (css) => {
  const compiled = compile(css, { inlineVariables: false });
  registerCSS(css, { inlineVariables: false });
  render(<View testID={testID} className="a" />);
  console.log(
    `${css} -> d ${JSON.stringify(compiled.stylesheet().s?.[0]?.[1][0]?.d)}; style ${JSON.stringify(StyleSheet.flatten(screen.getByTestId(testID).props.style))}; warnings ${JSON.stringify(compiled.warnings())}`,
  );
  screen.unmount();
});

src/__tests__/native/unresolved-variable-in-list.test.tsx:

import { StyleSheet } from "react-native";

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

jest.mock("../../native/reanimated", () => ({
  animatedComponentFamily: (component: unknown) => component,
}));

test.each([true, false])(
  "transition-property: var(--missing), height is invalid as a whole (inlineVariables: %s)",
  (inlineVariables) => {
    registerCSS(`.a { transition-property: var(--missing), height; transition-duration: 1s, 2s; }`, {
      inlineVariables,
    });
    render(<View testID={testID} className="a" />);
    const style = StyleSheet.flatten(screen.getByTestId(testID).props.style) as Record<string, unknown>;
    console.log(JSON.stringify(style));
    expect(style.transitionProperty).toBeUndefined();
  },
);

Expected: transition-property: var(--missing), height is invalid as a whole and computes to all, and a list with an item the compiler cannot read is dropped whole.

Actual: the list shortens and its entries move off their index: transitionProperty: ["height"] beside [1000, 2000], and ease-in applies to both properties.

PASS src/__tests__/native/unreadable-item.test.tsx
  ● Console
    console.log
      .a { transition-property: opacity, width; transition-duration: 1s; transition-timing-function: linear(0, 1), ease-in; } -> d [{"transitionProperty":["opacity","width"],"transitionDuration":[1000],"transitionTimingFunction":"ease-in"}]; style {"transitionProperty":["opacity","width"],"transitionDuration":[1000],"transitionTimingFunction":"ease-in"}; warnings {"values":{"transition-timing-function":["linear()"]}}
      at log (src/__tests__/native/unreadable-item.test.tsx:20:11)
    console.log
      .a { --e: ease-in; transition-property: opacity, width; transition-duration: 1s; transition-timing-function: linear(0, 1), var(--e); } -> d [{"transitionProperty":["opacity","width"],"transitionDuration":[1000]},[[{},"var","e",1],"transitionTimingFunction",1]]; style {"transitionProperty":["opacity","width"],"transitionDuration":[1000],"transitionTimingFunction":"ease-in"}; warnings {"values":{"transition-timing-function":["linear()"]}}
      at log (src/__tests__/native/unreadable-item.test.tsx:20:11)
FAIL src/__tests__/native/unresolved-variable-in-list.test.tsx
  ● Console
    console.log
      {"transitionProperty":["height"],"transitionDuration":[1000,2000]}
      at log (src/__tests__/native/unresolved-variable-in-list.test.tsx:19:13)
    console.log
      {"transitionProperty":["height"],"transitionDuration":[1000,2000]}
      at log (src/__tests__/native/unresolved-variable-in-list.test.tsx:19:13)
  ● transition-property: var(--missing), height is invalid as a whole (inlineVariables: true)
    expect(received).toBeUndefined()
    Received: ["height"]
      18 |     const style = StyleSheet.flatten(screen.getByTestId(testID).props.style) as Record<string, unknown>;
      19 |     console.log(JSON.stringify(style));
    > 20 |     expect(style.transitionProperty).toBeUndefined();
         |                                      ^
      21 |   },
      22 | );
      23 |
      at toBeUndefined (src/__tests__/native/unresolved-variable-in-list.test.tsx:20:38)
  ● transition-property: var(--missing), height is invalid as a whole (inlineVariables: false)
    expect(received).toBeUndefined()
    Received: ["height"]
      18 |     const style = StyleSheet.flatten(screen.getByTestId(testID).props.style) as Record<string, unknown>;
      19 |     console.log(JSON.stringify(style));
    > 20 |     expect(style.transitionProperty).toBeUndefined();
         |                                      ^
      21 |   },
      22 | );
      23 |
      at toBeUndefined (src/__tests__/native/unresolved-variable-in-list.test.tsx:20:38)
Test Suites: 1 failed, 1 passed, 2 total
Tests:       2 failed, 2 passed, 4 total
Snapshots:   0 total
Time:        1.595 s, estimated 2 s
Ran all test suites matching /src\\__tests__\\native\\unreadable-item.test.tsx|src\\__tests__\\native\\unresolved-variable-in-list.test.tsx/i.

Reproducible example repository

https://github.com/YevheniiKotyrlo/react-native-css/tree/repro/533-unresolved-variable-drops-out-of-a-list