Flutter团队开发安装路径不一致时编译失败的问题（iOS）

从年初开始在项目中引入flutter，用其实现了部分简单的页面。
我们团队中Pod的使用和主流有些不一样，Pods目录是不写入.gitignore的😆。

原因：

当通过pod引入Flutter module并执行pod install 后，Pod Project中Flutter相关的Targrt配置里都会写入Flutter.xcframework的绝对路径；
再加上我们git没有忽略pod目录；
所以如果不同的电脑Flutter安装路径不同，就会编译报错，找不到Flutter.xcframework。

有比较简单的解决方案

Pods文件夹不要上传到git
或
确保各电脑的flutter安装路径统一，比如都是Users/flutter/，

由于我想了解下flutter的构建方式，因此决定通过编写脚本的方式解决这个问题

通过分析，看到路径的配置是在xxxxxx/flutter/packages/flutter_tools/bin/podhelper.rb这个脚本中(省略了无关的代码)

def flutter_additional_ios_build_settings(target)
    ...
  artifacts_dir = File.join('..', '..', '..', '..', 'bin', 'cache', 'artifacts', 'engine')
  debug_framework_dir = File.expand_path(File.join(artifacts_dir, 'ios', 'Flutter.xcframework'), __FILE__)
  release_framework_dir = File.expand_path(File.join(artifacts_dir, 'ios-release', 'Flutter.xcframework'), __FILE__)
  ...
  target.build_configurations.each do |build_configuration|
        ...
    # Skip other updates if it's not a Flutter plugin (transitive dependency).
    next unless target.dependencies.any? { |dependency| dependency.name == 'Flutter' }
    ...
    # Profile can't be derived from the CocoaPods build configuration. Use release framework (for linking only).
    configuration_engine_dir = build_configuration.type == :debug ? debug_framework_dir : release_framework_dir
    Dir.new(configuration_engine_dir).each_child do |xcframework_file|
      next if xcframework_file.start_with?('.') # Hidden file, possibly on external disk.
      if xcframework_file.end_with?('-simulator') # ios-arm64_x86_64-simulator
        build_configuration.build_settings['FRAMEWORK_SEARCH_PATHS[sdk=iphonesimulator*]'] = "\"#{configuration_engine_dir}/#{xcframework_file}\" $(inherited)"
      elsif xcframework_file.start_with?('ios-') # ios-arm64
        build_configuration.build_settings['FRAMEWORK_SEARCH_PATHS[sdk=iphoneos*]'] = "\"#{configuration_engine_dir}/#{xcframework_file}\" $(inherited)"
       # else Info.plist or another platform.
      end
    end
   ...
  end
end

如果能够修改这里脚本写入的路径，比如debug_framework_dir = File.join("$(Flutter_Install_Path)", 'bin', 'cache', 'artifacts', 'engine', 'ios', 'Flutter.xcframework')，然后只需要在xcconfig中定义不同的Flutter_Install_Path就可以解决问题了。

但是修改flutter中的脚本是比较危险的操作，因此决定通过编写脚本再次修改掉flutter写入的Flutter.xcframework路径。
方案还是比较简单的，下面直接给出步骤：

在Podfile同级目录创建一个文件Flutter_Path.xcconfig，写入自己电脑上Flutter安装路径kv （这个文件需要写入.gitignore)
```
Flutter_Install_Path = /Users/dadadongl/flutter
```

修改Podfile中的脚本（下面是修改前/后）

# 修改前
post_install do |installer|  
  flutter_post_install(installer) if defined?(flutter_post_install)
end

 # 修改后
 post_install do |installer|
   # 先执行flutter正常的脚本
   flutter_post_install(installer) if defined?(flutter_post_install)
 
   # 注入环境变量 & 修改flutter默认写入的framework search path

   # 遍历Pod中的Targets
   installer.pods_project.targets.each do |target|
 
     # 修改flutter.xcframework的引用路径配置 （后面这段脚本基本是基于flutter的脚本修改的，做到改动最少）
     # 跳过没有依赖'Flutter'的target
     next unless target.dependencies.any? { |dependency| dependency.name == 'Flutter' }

     # 构造使用了环境变量$(Flutter_Install_Path)"的search path
     debug_framework_dir = File.join("$(Flutter_Install_Path)", 'bin', 'cache', 'artifacts', 'engine', 'ios', 'Flutter.xcframework')
     release_framework_dir = File.join("$(Flutter_Install_Path)", 'bin', 'cache', 'artifacts', 'engine', 'ios-release', 'Flutter.xcframework')
     # 解析自定义的xcconfig文件，为了拿到Flutter安装路径
     xcconfig = Xcodeproj::Config.new("./Flutter_Path.xcconfig")
     flutter_DIR = xcconfig.attributes["Flutter_Install_Path"]
     
     # 拿到Flutter的安装绝对路径
     full_debug_framework_dir = File.join(flutter_DIR, 'bin', 'cache', 'artifacts', 'engine', 'ios', 'Flutter.xcframework')
     full_release_framework_dir = File.join(flutter_DIR, 'bin', 'cache', 'artifacts', 'engine', 'ios-release', 'Flutter.xcframework')
     
     # 遍历Target下的配置环境（Debug 、Release）
     target.build_configurations.each do |build_configuration|
       
       # 追加自定义环境变量到 Pod 库的 .xcconfig 文件，为了编译时能够识别$(Flutter_Install_Path)
       xcconfig_path = build_configuration.base_configuration_reference.real_path
       # 这里导入时相对pod.debug.xcconfig的路径
       File.write(xcconfig_path, "#include \"../../../Flutter_Path.xcconfig\"", mode: 'a')
       
       # 修改 FRAMEWORK_SEARCH_PATHS
       configuration_engine_dir = build_configuration.type == :debug ? debug_framework_dir : release_framework_dir
       full_configuration_engine_dir = build_configuration.type == :debug ? full_debug_framework_dir : full_release_framework_dir
      
       Dir.new(full_configuration_engine_dir).each_child do |xcframework_file|
         next if xcframework_file.start_with?('.') # Hidden file, possibly on external disk.
         
         if xcframework_file.end_with?('-simulator') # ios-arm64_x86_64-simulator
           build_configuration.build_settings['FRAMEWORK_SEARCH_PATHS[sdk=iphonesimulator*]'] = "\"#{configuration_engine_dir}/#{xcframework_file}\" $(inherited)"
         elsif xcframework_file.start_with?('ios-') # ios-arm64
           build_configuration.build_settings['FRAMEWORK_SEARCH_PATHS[sdk=iphoneos*]'] = "\"#{configuration_engine_dir}/#{xcframework_file}\" $(inherited)"
           # else Info.plist or another platform.
         end
       end 
     end
   end
 end

重新执行Pod install

通过上述步骤后，就会把Flutter_Install_Path = /Users/dadadongl/flutter注入各Pod Target，然后修改后的framework search path就可以找到正确的路径，并成功编译。

Flutter团队开发安装路径不一致时编译失败的问题（iOS）

原因：

有比较简单的解决方案

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