fix: skip unchanged native stylesheet reinitialization

CONTEXT.md

@@ -119,7 +119,7 @@ Metro integration:
 - Metro adds `css` as source extension and removes it from asset extensions.
 - Metro transformer handles the configured CSS entry file specially.
 - Metro transformer worker selection is lazy, cached per Expo/non-Expo config type, and follows Expo transformer paths or Expo-specific config markers.
-- Native platform CSS transforms into a JS module that calls `Uniwind.__reinit(...)`.
+- Native platform CSS transforms into a JS module that calls `Uniwind.__reinit(...)` with a fingerprint of the generated styles and themes. During development, the native runtime skips reinitialization when that fingerprint is unchanged.
 - Web platform CSS transforms into CSS plus web runtime setup.
 - Resolver swaps React Native component imports to Uniwind-aware implementations where needed.
 

packages/uniwind/src/bundler/adapters/metro/transformer.ts

@@ -5,6 +5,7 @@ import { Platform } from '@/common/consts'
 import type * as ExpoMetroConfig from '@expo/metro-config'
 import type * as MetroTransformWorker from 'metro-transform-worker'
 import type { JsTransformerConfig, JsTransformOptions } from 'metro-transform-worker'
+import { createHash } from 'node:crypto'
 import path from 'path'
 
 const cssArtifactPath = path.resolve(__dirname, '../../uniwind.css')
@@ -69,13 +70,20 @@ export const transform = async (
     await bundlerConfig.generateArtifacts(cssArtifactPath)
     const virtualCode = await compileCSS(bundlerConfig)
     const isWeb = bundlerConfig.platform === Platform.Web
+    const nativeStylesFingerprint = isWeb
+        ? undefined
+        : createHash('sha256')
+            .update(virtualCode)
+            .update('\0')
+            .update(bundlerConfig.stringifiedThemes)
+            .digest('hex')
 
     data = Buffer.from(
         isWeb
             ? virtualCode
             : [
                 `const { Uniwind } = require('uniwind');`,
-                `Uniwind.__reinit(rt => ${virtualCode}, ${bundlerConfig.stringifiedThemes});`,
+                `Uniwind.__reinit(rt => ${virtualCode}, ${bundlerConfig.stringifiedThemes}, '${nativeStylesFingerprint}');`,
             ].join(''),
         'utf-8',
     )

packages/uniwind/src/core/config/config.native.ts

@@ -8,6 +8,8 @@ import type { CSSVariables, GenerateStyleSheetsCallback, ThemeName } from '../ty
 import { UniwindConfigBuilder as UniwindConfigBuilderBase } from './config.common'
 
 class UniwindConfigBuilder extends UniwindConfigBuilderBase {
+    private stylesFingerprint: string | undefined
+
     constructor() {
         super()
     }
@@ -35,9 +37,18 @@ class UniwindConfigBuilder extends UniwindConfigBuilderBase {
         UniwindListener.notify([StyleDependency.Insets])
     }
 
-    protected __reinit(generateStyleSheetCallback: GenerateStyleSheetsCallback, themes: Array<string>) {
+    protected __reinit(
+        generateStyleSheetCallback: GenerateStyleSheetsCallback,
+        themes: Array<string>,
+        stylesFingerprint?: string,
+    ) {
+        if (__DEV__ && stylesFingerprint !== undefined && stylesFingerprint === this.stylesFingerprint) {
+            return
+        }
+
         super.__reinit(generateStyleSheetCallback, themes)
         UniwindStore.reinit(generateStyleSheetCallback, themes)
+        this.stylesFingerprint = stylesFingerprint
     }
 
     protected onThemeChange() {

packages/uniwind/tests/native/core/config.test.ts

@@ -0,0 +1,52 @@
+import { Uniwind } from '../../../src/core/config/config.native'
+import { UniwindStore } from '../../../src/core/native'
+import type { GenerateStyleSheetsCallback } from '../../../src/core/types'
+
+type UniwindForTest = typeof Uniwind & {
+    __reinit: (initialize: GenerateStyleSheetsCallback, themes: Array<string>, fingerprint?: string) => void
+}
+
+const uniwind = Uniwind as UniwindForTest
+const generateStyles = () => ({ scopedVars: {}, stylesheet: {}, vars: {} })
+
+describe('Uniwind native config', () => {
+    afterEach(() => {
+        jest.restoreAllMocks()
+    })
+
+    test('skips reinitialization when generated styles have not changed', () => {
+        const reinit = jest.spyOn(UniwindStore, 'reinit')
+        const initialize = jest.fn(generateStyles)
+
+        uniwind.__reinit(initialize, ['light', 'dark'], 'unchanged-styles')
+        uniwind.__reinit(initialize, ['light', 'dark'], 'unchanged-styles')
+
+        expect(reinit).toHaveBeenCalledTimes(1)
+    })
+
+    test('reinitializes when generated styles change', () => {
+        const reinit = jest.spyOn(UniwindStore, 'reinit')
+        const initialize = jest.fn(generateStyles)
+
+        uniwind.__reinit(initialize, ['light', 'dark'], 'styles-before')
+        uniwind.__reinit(initialize, ['light', 'dark'], 'styles-after')
+
+        expect(reinit).toHaveBeenCalledTimes(2)
+    })
+
+    test('retries the same generated styles after initialization fails', () => {
+        const initialize = jest.fn(generateStyles)
+        const reinit = jest
+            .spyOn(UniwindStore, 'reinit')
+            .mockImplementationOnce(() => {
+                throw new Error('initialization failed')
+            })
+
+        expect(() => uniwind.__reinit(initialize, ['light', 'dark'], 'retry-styles')).toThrow(
+            'initialization failed',
+        )
+        uniwind.__reinit(initialize, ['light', 'dark'], 'retry-styles')
+
+        expect(reinit).toHaveBeenCalledTimes(2)
+    })
+})