Move logic from user project's Podfile to a Ruby script in Flutter tools

[xster]

Writing out the logic into the user project's source controlled Podfile means we're locking the interpretation of .flutter-plugins which is ephemeral with the Flutter tools in time and it's no longer upgradable.

Since we know we're moving the .flutter-plugins content to support federated plugins (@amirh) we should make sure the users with existing projects can handle changes in the way .flutter-plugins is written to.

cc @zanderso @jmagman

[zanderso]

To what extent do we know whether users have manually edit the file?

[xster]

Hard to say. Though it is an issue users brought up #12754

[jmagman]

\cc @franciscojma86

[jmagman]

New prompt from flutter:

Warning: Podfile is out of date
  This can cause issues if your application depends on plugins that do not support iOS.
  See https://flutter.dev/docs/development/packages-and-plugins/developing-packages#plugin-platforms for details.
  If you have local Podfile edits you would like to keep, see https://github.com/flutter/flutter/issues/45197 for instructions.
To regenerate the Podfile, run:
  rm ios/Podfile

If you have custom Podfile edits you would like to keep, the easiest thing to do is to re-create your changes on top of the new generated one. If you are unable to do that, here is the generated Podfile that copies the correct version of the Flutter engine to the expected locations.
You can interleave that Ruby code into yours as needed:
Objective-C app:
https://github.com/flutter/flutter/blob/master/packages/flutter_tools/templates/cocoapods/Podfile-ios-objc
Swift:
https://github.com/flutter/flutter/blob/master/packages/flutter_tools/templates/cocoapods/Podfile-ios-swift

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

[jmagman]

The Podfile format has changed in 1.20 with #59044. This change was made to support plugins that do not support the iOS platform and was developed to hopefully prevent painful developer migrations like this to be necessary in the future by simplifying it, and moving more logic into the Flutter SDK.

The new Podfile looks different, but the key sections are the same.

target 'Runner'

There's a target 'Runner' section where you can add your custom pods to be embedded in your app. It calls a Ruby method flutter_install_all_ios_pods that now lives in the Flutter SDK and will take care of embedding your Flutter plugins and the Flutter.framework.

target 'Runner' do
  use_frameworks!
  use_modular_headers!

  flutter_install_all_ios_pods File.dirname(File.realpath(__FILE__))

# ADD YOUR CUSTOM PODS HERE!
end

For example, if you needed to include a pod like KeychainSwift:

target 'Runner' do
  use_frameworks!
  use_modular_headers!

  flutter_install_all_ios_pods File.dirname(File.realpath(__FILE__))

  pod 'KeychainSwift', '~> 19.0'
end

project 'Runner'

project 'Runner is still at the top and is unchanged. If you have flavors set up with custom build configurations, copy it from your old Podfile exactly.

project 'Runner', {
  'Debug' => :debug,
  'Profile' => :release,
  'Release' => :release,
}

for example, if you had a Staging build configuration:

project 'Runner', {
  'Debug' => :debug,
  'Profile' => :release,
  'Staging' => :release,
  'Release' => :release,
}

post_install

There's also a post_install section if you have custom build settings or other changes you want to make to your Pod targets. It calls a Ruby method flutter_additional_ios_build_settings that now lives in the Flutter SDK and will take care of setting ENABLE_BITCODE=NO and other build settings.

post_install do |installer|
  installer.pods_project.targets.each do |target|
    flutter_additional_ios_build_settings(target)
    # YOUR CUSTOM TARGET CODE HERE.
  end
end

for example, if your old Podfile set your plugins' SWIFT_VERSION:

post_install do |installer|
  installer.pods_project.targets.each do |target|
    flutter_additional_ios_build_settings(target)
    target.build_configurations.each do |config|
      config.build_settings['SWIFT_VERSION'] = '4.1'
    end
  end
end