Solvedflutter Multiple commands produce '/build/ios/Debug-iphonesimulator/Runner.app/Frameworks/Flutter.framework

When I want to debug the application in MacOs environment, it throw such error:

Multiple commands produce '/build/ios/Debug-iphonesimulator/Runner.app/Frameworks/Flutter.framework

1. Target 'Runner' has copy command from '/ios/Flutter/Flutter.framework' to '/build/ios/Debug-iphonesimulator/Runner.app/Frameworks/Flutter.framework'
2. That command depends on command in Target 'Runner': script phase “[CP] Embed Pods Frameworks”
   warning: ignoring duplicated output file: '//build/ios/Debug-iphonesimulator/Runner.app/Frameworks/Flutter.framework' (in target 'Runner')
   note: Using new build systemnote: Planning buildnote: Constructing build description

Mac 10.14 Beta
Xcode 10 beta

How to fix it? Thanks a lot

I was able to fix it by opening the Runner workspace project in Xcode 10. Then navigate to File, Workspace Settings and change the build system to Legacy Build System.

Affected projects

This issue affects all Flutter projects built using Xcode 10 that have a dependency on CocoaPods -- typically this means those that rely on plugins.

Workarounds

There are two workarounds:

• Option 1: Use the legacy build system . As noted by @gi097, open ios/Runner.xcworkspace, and change the build system to Legacy Build System.
• Option 2: Use the new Xcode 10 build system.
  1. Open ios/Runner.xcworkspace
  2. Select the Runner project in the project navigator sidebar.
  3. In the main view, select the Runner target, then select the Build Phases tab.
  4. Expand the Embed Frameworks phase and select Flutter.framework from the embedded frameworks list.
  5. Click - to remove Flutter.framework from the list (be sure to keep App.framework).

Root cause

When plugins are in use, there are two competing build actions that copy Flutter.framework into the build application Frameworks directory:

1. The Embed Frameworks build phase for the Runner project
2. The [CP] Embed Pods Frameworks build phase that pod install creates in the project.

Item (1) is there to ensure the framework is copied into the built app in the case where there are no plugins (and therefore no CocoaPods integration in the Xcode project). Item (2) is there because Flutter's podspec declares Flutter.framework as a vended_framework, and CocoaPods automatically adds a copy step for each such vended_framework in the transitive closure of CocoaPods dependencies.

Immediate fix

The immediate fix is for us to find a way to automatically opt back in to the legacy build fix until a longer-term better solution is in place. Previous betas supported -useNewBuildSystem=NO or -useModernBuildSystem=NO but looks like this is removed in the GM build. Looks like currently the way to do this is to add a key-value pair (<key>BuildSystemType</key><string>Original</string>) to ios/Runner.xcworkspace/xcshareddata/WorkspaceSettings.xcsettings.

Longer-term fix

The simplest option would be to eliminate Flutter.framework from the Embed Frameworks step above and always rely on pod install, even in the case where there are no plugin dependencies. We'd need to update Flutter tool to automatically edit existing projects to remove Flutter.framework from the Embed Frameworks step.

pro: simpler code. con: makes cocoapods a required install step for Flutter development, first run involves a huge and very slow download of their repo.

A slightly nicer option would be for us to automatically detect whether the project uses plugins or not, and edit the Xcode project to check for and remove Flutter.framework from the Embed Frameworks step automatically if plugins are in use or add it if not.

pro: better user experience. con: more complex code.

Either way, we need some mechanism to automatically edit the project.pbxproj file and remove the framework from the embed frameworks build step. Supporting adding it back in isn't much incremental work and results in a better experience.

/cc @tvolkert @gspencergoog @dnfield

If you're still seeing this error, you will need to migrate your Xcode project:

1. File > Workspace Settings... > Build System, change dropdown to New Build System (Default)
2. In your Podfile, add the line

install! 'cocoapods', :disable_input_output_paths => true

See https://github.com/flutter/flutter/blob/master/examples/platform_view/ios/Podfile for example.
3. In the Runner target "[CP] Embed Pods Framework" Build Phase, remove all Output Files.

Or you can do #1 and #2, then run pod install from the ios directory, and CocoaPods should remove that Output file in the build phase automatically.

@gincos If you don't have a Mac you can look at PR #33684 for an example of how to tweak the Xcode files manually. If you have a Mac, please follow the above steps instead!

1. Delete the file ios/Runner.xcworkspace/xcshareddata/WorkspaceSettings.xcsettings. This is what's happening under the covers with File > Workspace Settings... > Build System > New Build System (Default).
   https://github.com/flutter/flutter/pull/33684/files#diff-e7ad834b29956b3cbd9225dc81f2c06a
2. In your Podfile, add the line

install! 'cocoapods', :disable_input_output_paths => true

https://github.com/flutter/flutter/pull/33684/files#diff-4e7de62cf4dff9802f06b7f3cb120939

Hopefully your cloud pipeline should run pod install and take care of #3 above for you.

If you are still seeing the error, you can edit ios/Runner.xcodeproj/project.pbxproj to remove the output file manually. Please be careful doing this! The Xcode project file does not take kindly to corruption.
https://github.com/flutter/flutter/pull/33684/files#diff-e9e57f7f2e911a135acd8f08e79b20e1

thanks a lot! it works.