Adjust the position of require File.expand_path

[LinXunFeng]

On Podfile:

flutter_application_path = '../flutter_module'
load File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')

target 'OCProject' do
  # Comment the next line if you don't want to use dynamic frameworks
  use_frameworks!

  # Pods for OCProject
  # install_all_flutter_pods(flutter_application_path)
  # install_flutter_engine_pod(flutter_application_path)
  # install_flutter_application_pod(flutter_application_path)
  install_flutter_plugin_pods(flutter_application_path)

end

post_install do |installer|
  flutter_post_install(installer)
end

Encountering the following error after executing pod install:

pod install

[!] Invalid `Podfile` file: undefined method `flutter_relative_path_from_podfile' for #<Pod::Podfile:0x000000010e74c520 @defined_in_file=#<Pathname:/Users/lxf/gitHub/flutter_hybrid_bug/OCProject/Podfile>, @internal_hash={}, @root_target_definitions=[#<Pod::Podfile::TargetDefinition label=Pods>], @current_target_definition=#<Pod::Podfile::TargetDefinition label=Pods>>

  relative = flutter_relative_path_from_podfile(export_script_directory)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^.

 #  from /Users/lxf/gitHub/flutter_hybrid_bug/OCProject/Podfile:17
 #  -------------------------------------------
 #    # install_flutter_plugin_pods(flutter_application_path)
 >    install_flutter_application_pod(flutter_application_path)
 #
 #  -------------------------------------------

The flutter_relative_path_from_podfile method is in flutter_tools/bin/podhelper.rb, but now flutter_tools/bin/podhelper.rb is only required in install_all_flutter_pods in podhelper.rb.tmpl.

Sometimes we only need to use the install_flutter_plugin_pods method in podhelper.rb. For example, using Shorebird in an iOS hybird app scenario, we need to build Flutter.xcframework and App.xcframework and embed them into the iOS native project. In order to avoid unnecessary conflicts, use install_flutter_plugin_pods method to install Flutter plugin pods.

Shorebird - Code Push In Hybrid Apps

So I adjust the position of require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root).

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[christopherfujino]

any reason why this shouldn't be at the top of the file?

[LinXunFeng]

This line of code must be placed after the flutter_root method, otherwise the following error will be reported.

❯ pod install

[!] Invalid `Podfile` file: undefined local variable or method `flutter_root' for main:Object

require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)
                                                                                     ^^^^^^^^^^^^.

It is also used like this in Podfile-ios-objc.

flutter/packages/flutter_tools/templates/cocoapods/Podfile-ios-objc

Lines 13 to 26 in 67457e6

	def flutter_root
	generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'Generated.xcconfig'), __FILE__)
	unless File.exist?(generated_xcode_build_settings_path)
	raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure flutter pub get is executed first"
	end
	File.foreach(generated_xcode_build_settings_path) do |line|
	matches = line.match(/FLUTTER_ROOT\=(.*)/)
	return matches[1].strip if matches
	end
	raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Generated.xcconfig, then run flutter pub get"
	end
	require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)

[christopherfujino]

Ahh I see, makes sense

[christopherfujino]

Sometimes we only need to use the install_flutter_plugin_pods method in podhelper.rb. For example, using Shorebird in an iOS hybird app scenario, we need to build Flutter.xcframework and App.xcframework and embed them into the iOS native project. In order to avoid unnecessary conflicts, use install_flutter_plugin_pods method to install Flutter plugin pods.

@jmagman this code change seems ok to me, but probably more important, is this a supported workflow?

[jmagman]

Sometimes we only need to use the install_flutter_plugin_pods method in podhelper.rb. For example, using Shorebird in an iOS hybird app scenario, we need to build Flutter.xcframework and App.xcframework and embed them into the iOS native project. In order to avoid unnecessary conflicts, use install_flutter_plugin_pods method to install Flutter plugin pods.

@LinXunFeng can you explain this a bit more, I'm curious. Is the scenario that your hybrid app uses CocoaPods and needs the same pods between the native app and the Flutter module? So you'd rather pod install run only once and deal with all the version solving so they don't conflict? Or is there something else going on?

is this a supported workflow?

It's not "supported" but I wouldn't go out of my way to break it. This change LGTM.

[jmagman]

By the way, thank you so much for the test!

[christopherfujino]

LGTM

[LinXunFeng]

can you explain this a bit more, I'm curious. Is the scenario that your hybrid app uses CocoaPods and needs the same pods between the native app and the Flutter module? So you'd rather pod install run only once and deal with all the version solving so they don't conflict? Or is there something else going on?

@jmagman According to the various ways to integrate the Flutter module introduced in the document, our app initially used Option A to integrate the Flutter module. When using Shorebird, it requires switching to something like Option B.

shorebird release ios-framework-alpha

When using the above command, Shorebird will use its own modified Flutter framework and engine to build Flutter.xcframework and App.xcframework.

In my Flutter module, I use some Flutter plugins based on native third packages, such as sqflite, which relies on FMDB, and FMDB is a dependency in our native project.

Pod::Spec.new do |s|
  s.name             = 'sqflite'
  ...
  s.dependency 'FMDB', '>= 2.7.5'
  ...
end

https://github.com/tekartik/sqflite/blob/70d127224b33594963f2df51157ad4481d41a5a4/sqflite/ios/sqflite.podspec#L18

When using Option B to build xcframework, there will be FMDB.xcframework. I dragged these xcframeworks into Build Settings > Build Phases > Link Binary With Libraries.

The following error will occur when compiling.

Showing Recent Messages
Multiple commands produce '/Users/lxf/.../xxx.app/Frameworks/FMDB.framework'

And the Option B will miss some vendored_frameworks such as realm

Pod::Spec.new do |s|
  s.name                      = 'realm'
  ...
  s.vendored_frameworks       = 'realm_dart.xcframework'
  ...
end

https://github.com/realm/realm-dart/blob/47e1ee72a6182bc3d5c13c0bac588066fdc6fffb/flutter/realm_flutter/ios/realm.podspec#L33

Related feedback: #125530

I also tried to embed these vendored_frameworks through scripts, but this way is troublesome.

I have tried putting the s.dependency that the Flutter plugin depends on one by one into the Podfile of the native project, and no longer embedding these xcframeworks. This solution is not friendly, because I need to judge whether the native project already has the same dependency. If there is, it needs to be discarded.

Even if the above problem was solved, our app would crash as soon as it started. After investigation, I found that it was because connectivity_plus relied on ReachabilitySwift. I put its dependency in the Podfile of our native project, but what it requires is Reachability.xcframework.

dyld[31764]: Symbol not found: _$s12ReachabilityAAC10ConnectionO4wifiyA2DmFWC
  Referenced from: <8142F86E-4C9C-3513-AD29-D3522FC6677F> /Users/lxf/.../connectivity_plus.framework/connectivity_plus
  Expected in:     <DA318000-9A97-35AD-87EA-7C5B635DE010> /Users/lxf/.../Frameworks/Reachability.framework/Reachability

In addition, we also need to determine whether each xcframework is a static framework or a dynamic framework, otherwise it will not be installed and run on the iPhone.

Related feedback: #122183

Based on so many problems mentioned above, I finally chose to create a podspec file to declare dependencies on the already built Flutter.xcframework and App.xcframework, and then combined with install_flutter_plugin_pods
method to integrate native third packages. 😂