[oleksandrzavarzin-callstack]

Closes #565. It is a continuation of @thiagobrez's work from #566.

Summary

The private-CoreSVG decoder is now opt-in on Apple platforms. By default, no SVG source is compiled or linked, and the decoder is never registered with React Native's app-wide image loader.

 CocoaPods (podspec)
-  ios/SVG/** always compiled
+  ios/SVG/** excluded unless $RNBottomTabsEnableSVG = true
 SwiftPM (Package.swift)
-  ios/SVG compiled into react_native_bottom_tabs
+  BottomTabsSVG target only when RN_BOTTOM_TABS_ENABLE_SVG=1
 Expo config plugin
+  { "enableSVG": true } writes $RNBottomTabsEnableSVG = true into the Podfile
 codegen (package.json)
-  modulesConformingToProtocol: RCTImageDataDecoder → SvgDecoder
+  (removed, so imageDataDecoderClassNames is empty)

With the flag set, the tab view decodes SVG icons itself:

loadIcons
  if SVG request            → SVGIconLoader.decode → updateIcon
  else RCTImageLoader.load
    on error (opt-in only)  → SVGIconLoader.decode → updateIcon   # extensionless SVG URLs

How to opt in:

Setup	Opt-in
CocoaPods	$RNBottomTabsEnableSVG = true in the Podfile, before React Native configures pods, then pod install
Expo prebuild	["react-native-bottom-tabs", { "enableSVG": true }]
SwiftPM	RN_BOTTOM_TABS_ENABLE_SVG=1 in the environment when SwiftPM resolves packages

Changes on top of #566:

• Rebased on main.
• SwiftPM opt-in in Package.swift. SvgDecoder.h is removed from ios/include/module.modulemap.
• The verification artifacts (artifacts/issue-565/) are removed from the repository.
• TabViewProvider.swift is split for SwiftLint. The SVG helpers moved to ios/SVGIconLoader.swift.

Results

Tested with Xcode 27.0 on an iPhone simulator with iOS 26.5.

• Before (main): every iOS app links the CoreSVG code. CoreSVGWrapper and the base64 symbol names are in the binary.
• After, default: none of CoreSVGWrapper, SvgDecoder, CGSVGDocument, RNBottomTabsDecodeSVGData, or the base64 literals are in the app binary. RCTTabViewComponentView is present as a control. The Pods project has 0 ios/SVG files, and imageDataDecoderClassNames is empty. On the simulator, SF Symbol and PNG icons render, and SVG tabs show their titles with no icon.
• After, opt-in: _RNBottomTabsDecodeSVGData, CoreSVGWrapper, and the base64 literals are present. CocoaPods adds exactly CoreSVG.{h,mm} and SvgDecoder.{h,mm}. Local and remote SVG tab icons render on the simulator.

default SF Symbols	default SVG example (titles only)	opt-in local SVG	opt-in remote SVG

• Expo plugin, with four expo prebuild --platform ios runs: without the option there is no flag. With enableSVG: true, there is one generated block right after platform :ios. Removing the option removes the block.
• swift package dump-package without the variable has no BottomTabsSVG target. With RN_BOTTOM_TABS_ENABLE_SVG=1, it adds the target and the Swift define.
• yarn lint: 0 errors.
• yarn test: passes. It includes the new svg_configuration_test.rb with 3 runs and 7 assertions.
• yarn typecheck: passes.
• SwiftLint 0.65.1: 0 errors, and 53 warnings against 54 on main.

Before Merging

This is a breaking default, so it ships as a major changeset. After a release, apps that update depend on the new default.

Blast Radius: iOS SVG users

• Apps that use SVG tab icons on Apple platforms lose those icons after the upgrade until they add the flag and rebuild.
• Apps that used a plain React Native <Image> with an SVG source lose that as well. The decoder was app-wide before. It now serves only tab icons, even with the flag.
• SwiftPM: Xcode reads RN_BOTTOM_TABS_ENABLE_SVG only from its own environment. If Xcode was started from the Dock, a variable set in a shell does not reach it.