Set SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG in the Debug config - #244
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Set SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG in the Debug config#244radoslawrolka wants to merge 1 commit into
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The app template's AppDelegate.swift gates the Metro bundle URL behind `#if DEBUG` (falling back to a non-existent main.jsbundle otherwise). In Swift, `#if DEBUG` is controlled by SWIFT_ACTIVE_COMPILATION_CONDITIONS, not by GCC_PREPROCESSOR_DEFINITIONS (which only affects C/ObjC/C++). Today this flag is not committed in project.pbxproj; it is injected at `pod install` time by react_native_post_install (react_native_pods.rb), which calls set_build_setting for SWIFT_ACTIVE_COMPILATION_CONDITIONS = ["$(inherited)", "DEBUG"] on the user project's Debug config. That means any setup that does not run CocoaPods (e.g. Swift Package Manager react-native experimental setup) never gets the flag, so `#if DEBUG` is false even in Debug builds. bundleURL() then returns nil and the app fails to launch with "No script url provided ... unsanitizedScriptURLString = (null)", even though Metro is running. Baking the setting into the template makes Debug builds work regardless of the dependency manager and matches the value CocoaPods already sets, so CocoaPods-based apps are unaffected.
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I think we should merge this one, @radoslawrolka :) Makes a lot of sense - since this is the App's code it should be here - and not in the SwiftPM manifest generators. |
radoslawrolka
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July 24, 2026 07:58
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cipolleschi
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Aug 12, 2026
cipolleschi
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thanks for the PR. however, that's not the best way to handle it as everyone would have to modify their project. A better way would be to open a PR against React Native and modify the scripts that configure the project to add that flag.
Do you mind doing that?
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Created the react/react-native#57914 |
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…57914) Summary: Swift's `#if DEBUG` is gated by SWIFT_ACTIVE_COMPILATION_CONDITIONS, not by GCC_PREPROCESSOR_DEFINITIONS (which only reaches C/ObjC/C++). The app template does not commit that setting; CocoaPods injects it at `pod install` time (react_native_post_install -> set_build_setting SWIFT_ACTIVE_COMPILATION_CONDITIONS = ["$(inherited)", "DEBUG"] on Debug). An app set up with the experimental SwiftPM support never runs CocoaPods, so `#if DEBUG` is false even in a Debug build: AppDelegate.swift's `bundleURL()` skips the Metro URL and falls back to a main.jsbundle a Debug build never produced, and the app dies at launch with "No script url provided ... unsanitizedScriptURLString = (null)" while Metro is running. Info: react-native-community/template#244 ## Changelog: Inject the setting from `spm add`/`update` alongside the other React build settings, into debug-flavored configurations only (the same flavorForBuildConfiguration test that selects the debug xcframeworks), so a config linking the debug binaries also compiles its Swift with DEBUG. <!-- Help reviewers and the release process by writing your own changelog entry. Pick one each for the category and type tags: [IOS] [FIXED] - Set SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG when injecting SPM For more details, see: https://reactnative.dev/contributing/changelogs-in-pull-requests Pull Request resolved: #57914 Test Plan: 1. Build spm-only rn app in debug - App will fail to connect to the Metro 2. Apply changes and run `react-native spm` 3. Build again - App will work as expected in debug and Metro will be connected Reviewed By: Abbondanzo Differential Revision: D115736551 Pulled By: cipolleschi fbshipit-source-id: 1e42ca26ac1992bfa827ce85a63cf4564d313e15
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Continuation in react/react-native#57914
## Summary:The app template's AppDelegate.swift gates the Metro bundle URL behind#if DEBUG(falling back to a non-existent main.jsbundle otherwise). In Swift,#if DEBUGis controlled by SWIFT_ACTIVE_COMPILATION_CONDITIONS, not by GCC_PREPROCESSOR_DEFINITIONS (which only affects C/ObjC/C++).Today this flag is not committed in project.pbxproj; it is injected atpod installtime by react_native_post_install (react_native_pods.rb), which calls set_build_setting for SWIFT_ACTIVE_COMPILATION_CONDITIONS = ["$(inherited)", "DEBUG"] on the user project's Debug config.That means any setup that does not run CocoaPods (e.g. Swift Package Manager react-native experimental setup) never gets the flag, so#if DEBUGis false even in Debug builds. bundleURL() then returns nil and the app fails to launch with "No script url provided ... unsanitizedScriptURLString = (null)", even though Metro is running.Baking the setting into the template makes Debug builds work regardless of the dependency manager and matches the value CocoaPods already sets, so CocoaPods-based apps are unaffected.## Changelog:[IOS] [FIXED] - added missing SWIFT_ACTIVE_COMPILATION_CONDITIONS in debug config## Test Plan:building app without coocapods (react/react-native #57332)