Remove enableOptimizedBoxShadowParsing feature flag (facebook#56098)

Summary:
Pull Request resolved: facebook#56098

changelog: [internal]

Delete the `enableOptimizedBoxShadowParsing` flag and enable the optimized box shadow parsing by default. The optimization hoists regex patterns to module scope in `processBoxShadow.js`. Impact in production was small since this is a minor perf improvement to regex compilation.

Reviewed By: javache

Differential Revision: D96594041

fbshipit-source-id: 3ecf2e68a063e831f50ce9137155c7255495327f

Author: sammy-SC

packages/react-native/Libraries/StyleSheet/__tests__/processBoxShadow-itest.js

@@ -5,7 +5,6 @@
  * LICENSE file in the root directory of this source tree.
  *
  * @flow strict-local
- * @fantom_flags enableOptimizedBoxShadowParsing:*
  * @format
  */
 

packages/react-native/Libraries/StyleSheet/processBoxShadow.js

@@ -11,10 +11,8 @@
 import type {ProcessedColorValue} from './processColor';
 import type {BoxShadowValue} from './StyleSheetTypes';
 
-import {enableOptimizedBoxShadowParsing} from '../../src/private/featureflags/ReactNativeFeatureFlags';
 import processColor from './processColor';
 
-// Pre-compiled regex patterns for performance - avoids regex compilation on each call
 const COMMA_SPLIT_REGEX = /,(?![^()]*\))/;
 const WHITESPACE_SPLIT_REGEX = /\s+(?![^(]*\))/;
 const LENGTH_PARSE_REGEX = /^([+-]?\d*\.?\d+)(px)?$/;
@@ -39,12 +37,7 @@ export default function processBoxShadow(
 
   const boxShadowList =
     typeof rawBoxShadows === 'string'
-      ? parseBoxShadowString(
-          rawBoxShadows.replace(
-            enableOptimizedBoxShadowParsing() ? NEWLINE_REGEX : /\n/g,
-            ' ',
-          ),
-        )
+      ? parseBoxShadowString(rawBoxShadows.replace(NEWLINE_REGEX, ' '))
       : rawBoxShadows;
 
   for (const rawBoxShadow of boxShadowList) {
@@ -121,9 +114,7 @@ function parseBoxShadowString(rawBoxShadows: string): Array<BoxShadowValue> {
   let result: Array<BoxShadowValue> = [];
 
   for (const rawBoxShadow of rawBoxShadows
-    .split(
-      enableOptimizedBoxShadowParsing() ? COMMA_SPLIT_REGEX : /,(?![^()]*\))/,
-    ) // split by comma that is not in parenthesis
+    .split(COMMA_SPLIT_REGEX)
     .map(bS => bS.trim())
     .filter(bS => bS !== '')) {
     const boxShadow: BoxShadowValue = {
@@ -137,11 +128,7 @@ function parseBoxShadowString(rawBoxShadows: string): Array<BoxShadowValue> {
     let lengthCount = 0;
 
     // split rawBoxShadow string by all whitespaces that are not in parenthesis
-    const args = rawBoxShadow.split(
-      enableOptimizedBoxShadowParsing()
-        ? WHITESPACE_SPLIT_REGEX
-        : /\s+(?![^(]*\))/,
-    );
+    const args = rawBoxShadow.split(WHITESPACE_SPLIT_REGEX);
     for (const arg of args) {
       const processedColor = processColor(arg);
       if (processedColor != null) {
@@ -210,43 +197,18 @@ function parseBoxShadowString(rawBoxShadows: string): Array<BoxShadowValue> {
 }
 
 function parseLength(length: string): ?number {
-  if (enableOptimizedBoxShadowParsing()) {
-    // Use pre-compiled regex for performance
-    const match = LENGTH_PARSE_REGEX.exec(length);
+  const match = LENGTH_PARSE_REGEX.exec(length);
 
-    if (!match) {
-      return null;
-    }
-
-    const value = parseFloat(match[1]);
-    if (Number.isNaN(value)) {
-      return null;
-    }
-
-    // match[2] is 'px' or undefined
-    // If no unit and value is not 0, return null
-    if (match[2] == null && value !== 0) {
-      return null;
-    }
-
-    return value;
-  }
-
-  // matches on args with units like "1.5 5% -80deg"
-  const argsWithUnitsRegex = /([+-]?\d*(\.\d+)?)([\w\W]+)?/g;
-  const match = argsWithUnitsRegex.exec(length);
-
-  if (!match || Number.isNaN(match[1])) {
+  if (!match) {
     return null;
   }
 
-  if (match[3] != null && match[3] !== 'px') {
-    return null;
-  }
+  const value = parseFloat(match[1]);
 
-  if (match[3] == null && match[1] !== '0') {
+  // If no unit (px) and value is not 0, reject it
+  if (match[2] == null && value !== 0) {
     return null;
   }
 
-  return Number(match[1]);
+  return value;
 }

packages/react-native/scripts/featureflags/ReactNativeFeatureFlags.config.js

@@ -1054,17 +1054,6 @@ const definitions: FeatureFlagDefinitions = {
       },
       ossReleaseStage: 'none',
     },
-    enableOptimizedBoxShadowParsing: {
-      defaultValue: false,
-      metadata: {
-        dateAdded: '2026-02-26',
-        description:
-          'Hoists regex patterns to module scope and optimizes parseLength in processBoxShadow for improved performance.',
-        expectedReleaseValue: true,
-        purpose: 'experimentation',
-      },
-      ossReleaseStage: 'none',
-    },
     externalElementInspectionEnabled: {
       defaultValue: true,
       metadata: {

packages/react-native/src/private/featureflags/ReactNativeFeatureFlags.js

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<5966ef11ee71a38059decda1c529fd6f>>
+ * @generated SignedSource<<0fffffdeaf8ab7210131ac789f8b208b>>
  * @flow strict
  * @noformat
  */
@@ -33,7 +33,6 @@ export type ReactNativeFeatureFlagsJsOnly = $ReadOnly<{
   animatedShouldUseSingleOp: Getter<boolean>,
   deferFlatListFocusChangeRenderUpdate: Getter<boolean>,
   disableMaintainVisibleContentPosition: Getter<boolean>,
-  enableOptimizedBoxShadowParsing: Getter<boolean>,
   externalElementInspectionEnabled: Getter<boolean>,
   fixImageSrcDimensionPropagation: Getter<boolean>,
   fixVirtualizeListCollapseWindowSize: Getter<boolean>,
@@ -165,11 +164,6 @@ export const deferFlatListFocusChangeRenderUpdate: Getter<boolean> = createJavaS
  */
 export const disableMaintainVisibleContentPosition: Getter<boolean> = createJavaScriptFlagGetter('disableMaintainVisibleContentPosition', false);
 
-/**
- * Hoists regex patterns to module scope and optimizes parseLength in processBoxShadow for improved performance.
- */
-export const enableOptimizedBoxShadowParsing: Getter<boolean> = createJavaScriptFlagGetter('enableOptimizedBoxShadowParsing', false);
-
 /**
  * Enable the external inspection API for DevTools to communicate with the Inspector overlay.
  */