RN: Represent Numeric Feature Flags as Double (#51713)

Summary:
Pull Request resolved: #51713

Changes the React Native Feature Flags system so that numeric feature flags are represented in native languages as double instead of int, in order to avoid loss of precision for non-integral JavaScript numbers.

Changelog:
[Internal]

Reviewed By: mdvacca

Differential Revision: D75709111

fbshipit-source-id: d4b2d553ce1e719a5f4b136a4f8d2e46446ef8d8

Author: yungsters

packages/react-native/scripts/featureflags/templates/android/ReactNativeFeatureFlagsDefaults.kt-template.js

@@ -13,6 +13,7 @@ import type {FeatureFlagDefinitions} from '../../types';
 import {
   DO_NOT_MODIFY_COMMENT,
   getKotlinTypeFromDefaultValue,
+  getKotlinValueFromDefaultValue,
 } from '../../utils';
 import signedsource from 'signedsource';
 
@@ -39,7 +40,7 @@ ${Object.entries(definitions.common)
     ([flagName, flagConfig]) =>
       `  override fun ${flagName}(): ${getKotlinTypeFromDefaultValue(
         flagConfig.defaultValue,
-      )} = ${JSON.stringify(flagConfig.defaultValue)}`,
+      )} = ${getKotlinValueFromDefaultValue(flagConfig.defaultValue)}`,
   )
   .join('\n\n')}
 }

packages/react-native/scripts/featureflags/templates/android/ReactNativeFeatureFlagsOverrides_RNOSS__Stage__Android.kt-template.js

@@ -13,6 +13,7 @@ import type {FeatureFlagDefinitions, OSSReleaseStageValue} from '../../types';
 import {
   DO_NOT_MODIFY_COMMENT,
   getKotlinTypeFromDefaultValue,
+  getKotlinValueFromDefaultValue,
 } from '../../utils';
 import signedsource from 'signedsource';
 
@@ -52,7 +53,7 @@ ${Object.entries(definitions.common)
     if (flagConfig.ossReleaseStage === ossReleaseStage) {
       return `  override fun ${flagName}(): ${getKotlinTypeFromDefaultValue(
         flagConfig.metadata.expectedReleaseValue,
-      )} = ${JSON.stringify(flagConfig.metadata.expectedReleaseValue)}`;
+      )} = ${getKotlinValueFromDefaultValue(flagConfig.metadata.expectedReleaseValue)}`;
     }
   })
   .filter(Boolean)

packages/react-native/scripts/featureflags/templates/common-cxx/ReactNativeFeatureFlagsDefaults.h-template.js

@@ -10,7 +10,11 @@
 
 import type {FeatureFlagDefinitions} from '../../types';
 
-import {DO_NOT_MODIFY_COMMENT, getCxxTypeFromDefaultValue} from '../../utils';
+import {
+  DO_NOT_MODIFY_COMMENT,
+  getCxxTypeFromDefaultValue,
+  getCxxValueFromDefaultValue,
+} from '../../utils';
 import signedsource from 'signedsource';
 
 export default function (definitions: FeatureFlagDefinitions): string {
@@ -41,7 +45,7 @@ ${Object.entries(definitions.common)
       `  ${getCxxTypeFromDefaultValue(
         flagConfig.defaultValue,
       )} ${flagName}() override {
-    return ${JSON.stringify(flagConfig.defaultValue)};
+    return ${getCxxValueFromDefaultValue(flagConfig.defaultValue)};
   }`,
   )
   .join('\n\n')}

packages/react-native/scripts/featureflags/templates/common-cxx/ReactNativeFeatureFlagsDynamicProvider.h-template.js

@@ -8,27 +8,15 @@
  * @format
  */
 
-import type {
-  CommonFeatureFlagConfig,
-  FeatureFlagDefinitions,
-} from '../../types';
+import type {FeatureFlagDefinitions} from '../../types';
 
-import {DO_NOT_MODIFY_COMMENT, getCxxTypeFromDefaultValue} from '../../utils';
+import {
+  DO_NOT_MODIFY_COMMENT,
+  getCxxFollyDynamicAccessorFromDefaultValue,
+  getCxxTypeFromDefaultValue,
+} from '../../utils';
 import signedsource from 'signedsource';
 
-function getFollyDynamicAccessor(config: CommonFeatureFlagConfig<>): string {
-  switch (typeof config.defaultValue) {
-    case 'boolean':
-      return 'getBool';
-    case 'number':
-      return 'getInt';
-    case 'string':
-      return 'getString';
-    default:
-      throw new Error(`Unsupported type: ${typeof config.defaultValue}`);
-  }
-}
-
 export default function (definitions: FeatureFlagDefinitions): string {
   return signedsource.signFile(`/*
  * Copyright (c) Meta Platforms, Inc. and affiliates.
@@ -77,7 +65,7 @@ ${Object.entries(definitions.common)
       )} ${flagName}() override {
     auto value = values_["${flagName}"];
     if (!value.isNull()) {
-      return value.${getFollyDynamicAccessor(flagConfig)}();
+      return value.${getCxxFollyDynamicAccessorFromDefaultValue(flagConfig.defaultValue)}();
     }
 
     return ReactNativeFeatureFlagsDefaults::${flagName}();

packages/react-native/scripts/featureflags/templates/common-cxx/ReactNativeFeatureFlagsOverridesOSS_Stage_.h-template.js

@@ -10,7 +10,11 @@
 
 import type {FeatureFlagDefinitions, OSSReleaseStageValue} from '../../types';
 
-import {DO_NOT_MODIFY_COMMENT, getCxxTypeFromDefaultValue} from '../../utils';
+import {
+  DO_NOT_MODIFY_COMMENT,
+  getCxxTypeFromDefaultValue,
+  getCxxValueFromDefaultValue,
+} from '../../utils';
 import signedsource from 'signedsource';
 
 function getClassName(ossReleaseStage: OSSReleaseStageValue): string {
@@ -64,7 +68,7 @@ ${Object.entries(definitions.common)
       return `  ${getCxxTypeFromDefaultValue(
         flagConfig.metadata.expectedReleaseValue,
       )} ${flagName}() override {
-    return ${JSON.stringify(flagConfig.metadata.expectedReleaseValue)};
+    return ${getCxxValueFromDefaultValue(flagConfig.metadata.expectedReleaseValue)};
   }`;
     }
   })

packages/react-native/scripts/featureflags/templates/js/NativeReactNativeFeatureFlags.cpp-template.js

@@ -10,7 +10,11 @@
 
 import type {FeatureFlagDefinitions} from '../../types';
 
-import {DO_NOT_MODIFY_COMMENT, getCxxTypeFromDefaultValue} from '../../utils';
+import {
+  DO_NOT_MODIFY_COMMENT,
+  getCxxTypeFromDefaultValue,
+  getCxxValueFromDefaultValue,
+} from '../../utils';
 import signedsource from 'signedsource';
 
 export default function (definitions: FeatureFlagDefinitions): string {
@@ -54,7 +58,7 @@ ${Object.entries(definitions.common)
     jsi::Runtime& /*runtime*/) {
   // This flag is configured with \`skipNativeAPI: true\`.
   // TODO(T204838867): Implement support for optional methods in C++ TM codegen and remove the method definition altogether.
-  return ${JSON.stringify(flagConfig.defaultValue)};
+  return ${getCxxValueFromDefaultValue(flagConfig.defaultValue)};
 }`
       : `${getCxxTypeFromDefaultValue(
           flagConfig.defaultValue,

packages/react-native/scripts/featureflags/utils.js

@@ -17,22 +17,55 @@ export function getCxxTypeFromDefaultValue(
     case 'boolean':
       return 'bool';
     case 'number':
-      return 'int';
+      return 'double';
     case 'string':
       return 'std::string';
     default:
       throw new Error(`Unsupported default value type: ${typeof defaultValue}`);
   }
 }
 
+export function getCxxValueFromDefaultValue(
+  defaultValue: FeatureFlagValue,
+): string {
+  switch (typeof defaultValue) {
+    case 'boolean':
+      return defaultValue.toString();
+    case 'number':
+      const numericString = defaultValue.toString();
+      // If the number is an integer, we need to append ".0" so that the result
+      // is interpeted as a double in C++.
+      return numericString.includes('.') ? numericString : `${numericString}.0`;
+    case 'string':
+      return JSON.stringify(defaultValue);
+    default:
+      throw new Error(`Unsupported default value type: ${typeof defaultValue}`);
+  }
+}
+
+export function getCxxFollyDynamicAccessorFromDefaultValue(
+  defaultValue: FeatureFlagValue,
+): string {
+  switch (typeof defaultValue) {
+    case 'boolean':
+      return 'getBool';
+    case 'number':
+      return 'getDouble';
+    case 'string':
+      return 'getString';
+    default:
+      throw new Error(`Unsupported default value type: ${typeof defaultValue}`);
+  }
+}
+
 export function getCxxJNITypeFromDefaultValue(
   defaultValue: FeatureFlagValue,
 ): string {
   switch (typeof defaultValue) {
     case 'boolean':
       return 'jboolean';
     case 'number':
-      return 'jint';
+      return 'jdouble';
     case 'string':
       return 'jstring';
     default:
@@ -47,14 +80,32 @@ export function getKotlinTypeFromDefaultValue(
     case 'boolean':
       return 'Boolean';
     case 'number':
-      return 'Int';
+      return 'Double';
     case 'string':
       return 'String';
     default:
       throw new Error(`Unsupported default value type: ${typeof defaultValue}`);
   }
 }
 
+export function getKotlinValueFromDefaultValue(
+  defaultValue: FeatureFlagValue,
+): string {
+  switch (typeof defaultValue) {
+    case 'boolean':
+      return defaultValue.toString();
+    case 'number':
+      const numericString = defaultValue.toString();
+      // If the number is an integer, we need to append ".0" so that the result
+      // is interpeted as a double in Kotlin.
+      return numericString.includes('.') ? numericString : `${numericString}.0`;
+    case 'string':
+      return JSON.stringify(defaultValue);
+    default:
+      throw new Error(`Unsupported default value type: ${typeof defaultValue}`);
+  }
+}
+
 export const DO_NOT_MODIFY_COMMENT = `/**
  * IMPORTANT: Do NOT modify this file directly.
  *