2. 整体把握 CocoaPods 核心组件

SKIP_UNRELEASED_VERSIONS = false
# ...

source 'https://rubygems.org'
gemspec
gem 'json', :git => 'https://github.com/segiddins/json.git', :branch => 'seg-1.7.7-ruby-2.2'

group :development do
  cp_gem 'claide',                'CLAide'
  cp_gem 'cocoapods-core',        'Core', '1-9-stable'
  cp_gem 'cocoapods-deintegrate', 'cocoapods-deintegrate'
  cp_gem 'cocoapods-downloader',  'cocoapods-downloader'
  cp_gem 'cocoapods-plugins',     'cocoapods-plugins'
  cp_gem 'cocoapods-search',      'cocoapods-search'
  cp_gem 'cocoapods-stats',       'cocoapods-stats'
  cp_gem 'cocoapods-trunk',       'cocoapods-trunk'
  cp_gem 'cocoapods-try',         'cocoapods-try'
  cp_gem 'molinillo',             'Molinillo'
  cp_gem 'nanaimo',               'Nanaimo'
  cp_gem 'xcodeproj',             'Xcodeproj'
   
  gem 'cocoapods-dependencies', '~> 1.0.beta.1'
  # ...
  # Integration tests
  gem 'diffy'
  gem 'clintegracon'
  # Code Quality
  gem 'inch_by_inch'
  gem 'rubocop'
  gem 'danger'
end

group :debugging do
  gem 'cocoapods_debug'

  gem 'rb-fsevent'
  gem 'kicker'
  gem 'awesome_print'
  gem 'ruby-prof', :platforms => [:ruby]
end

def cp_gem(name, repo_name, branch = 'master', path: false)
  return gem name if SKIP_UNRELEASED_VERSIONS
  opts = if path
           { :path => "../#{repo_name}" }
         else
           url = "https://github.com/CocoaPods/#{repo_name}.git"
           { :git => url, :branch => branch }
         end
  gem name, opts
end

$ ls -l
lrwxr-xr-x  1 gua  staff    31 Jul 30 21:34 CocoaPods
lrwxr-xr-x  1 gua  staff    26 Jul 31 13:27 Core 
lrwxr-xr-x  1 gua  staff    31 Jul 31 10:14 Molinillo 
lrwxr-xr-x  1 gua  staff    31 Aug 15 11:32 Xcodeproj 
lrwxr-xr-x  1 gua  staff    42 Jul 31 10:14 cocoapods-downloader

$ which pod
/Users/edmond/.rvm/gems/ruby-2.6.1/bin/pod

$ cat /Users/edmond/.rvm/gems/ruby-2.6.1/bin/pod

#!/usr/bin/env ruby_executable_hooks

require 'rubygems'
version = ">= 0.a"

str = ARGV.first
if str
  str = str.b[/\A_(.*)_\z/, 1]
  if str and Gem::Version.correct?(str)
    version = str
    ARGV.shift
  end
end

if Gem.respond_to?(:activate_bin_path)
    load Gem.activate_bin_path('cocoapods', 'pod', version)
else
    gem "cocoapods", version
    load Gem.bin_path("cocoapods", "pod", version)
end

#!/usr/bin/env ruby
# ... 忽略一些对于编码处理的代码

require 'cocoapods'

# 这里手动输出一下调用栈，来关注一下
puts caller

# 如果环境配置中指定了 ruby-prof 配置文件，会对执行命令过程进行性能监控
if profile_filename = ENV['COCOAPODS_PROFILE']
  require 'ruby-prof'
  # 依据配置文件类型加载不同的 reporter 解析器
  # ...
  File.open(profile_filename, 'w') do |io|
    reporter.new(RubyProf.profile { Pod::Command.run(ARGV) }).print(io)
  end
else
  Pod::Command.run(ARGV)
end

$ pod
/Users/edmond/.rvm/gems/ruby-2.6.1/bin/pod:24:in `load'
/Users/edmond/.rvm/gems/ruby-2.6.1/bin/pod:24:in `<main>'
/Users/edmond/.rvm/gems/ruby-2.6.1/bin/ruby_executable_hooks:24:in `eval'
/Users/edmond/.rvm/gems/ruby-2.6.1/bin/ruby_executable_hooks:24:in `<main>'

module Pod
  class Command
    class Install < Command
      # ... 
      def run
        # 判断是否存在 Podfile 文件
        verify_podfile_exists!
        # 从 Config 中获取一个 Instraller 实例
        installer = installer_for_config
        # 默认是不执行 update
        installer.repo_update = repo_update?(:default => false)
        installer.update = false
        installer.deployment = @deployment
        # install 的真正过程
        installer.install!
      end
    end
  end
end

def install!
    prepare
    resolve_dependencies
    download_dependencies
    validate_targets
    if installation_options.skip_pods_project_generation?
        show_skip_pods_project_generation_message
    else
        integrate
    end
    write_lockfiles
    perform_post_install_actions
end

def integrate
    generate_pods_project
    if installation_options.integrate_targets?
        integrate_user_project
    else
        UI.section 'Skipping User Project Integration'
    end
end

def prepare
  # 如果检测出当前目录是 Pods，直接 raise 终止
  if Dir.pwd.start_with?(sandbox.root.to_path)
    message = 'Command should be run from a directory outside Pods directory.'
    message << "\n\n\tCurrent directory is #{UI.path(Pathname.pwd)}\n"
    raise Informative, message
  end
  UI.message 'Preparing' do
    # 如果 lock 文件的 CocoaPods 主版本和当前版本不同，将以新版本的配置对 xcodeproj 工程文件进行更新
    deintegrate_if_different_major_version
    # 对 sandbox(Pods) 目录建立子目录结构
    sandbox.prepare
    # 检测 PluginManager 是否有 pre-install 的 plugin
    ensure_plugins_are_installed!
    # 执行插件中 pre-install 的所有 hooks 方法
    run_plugins_pre_install_hooks
  end
end

def resolve_dependencies
    # 获取 Sources
    plugin_sources = run_source_provider_hooks
    # 创建一个 Analyzer
    analyzer = create_analyzer(plugin_sources)

    # 如果带有 repo_update 标记
    UI.section 'Updating local specs repositories' do
        # 执行 Analyzer 的更新 Repo 操作
        analyzer.update_repositories
    end if repo_update?

    UI.section 'Analyzing dependencies' do
        # 从 analyzer 取出最新的分析结果，@analysis_result，@aggregate_targets，@pod_targets
        analyze(analyzer)
        # 拼写错误降级识别，白名单过滤
        validate_build_configurations
    end

    # 如果 deployment? 为 true，会验证 podfile & lockfile 是否需要更新
    UI.section 'Verifying no changes' do
        verify_no_podfile_changes!
        verify_no_lockfile_changes!
    end if deployment?
 
    analyzer
end

def download_dependencies
  UI.section 'Downloading dependencies' do
    # 初始化 sandbox 文件访问器
    create_file_accessors
    # 构造 Pod Source Installer
    install_pod_sources
    # 执行 podfile 定义的 pre install 的 hooks
    run_podfile_pre_install_hooks
    # 根据配置清理 pod sources 信息，主要是清理无用 platform 相关内容
    clean_pod_sources
  end
end

def install_pod_sources
 @installed_specs = []
 # install 的 Pod 只需要这两种状态，added 和 changed 状态的并集
 pods_to_install = sandbox_state.added | sandbox_state.changed
 title_options = { :verbose_prefix => '-> '.green }
 puts "root_specs"
 root_specs.each do |item|
   puts item
 end
 # 将 Podfile 解析后排序处理
 root_specs.sort_by(&:name).each do |spec|
   # 如果是 added 或 changed 状态的 Pod
   if pods_to_install.include?(spec.name)
     # 如果是 changed 状态并且 manifest 已经有记录
     if sandbox_state.changed.include?(spec.name) && sandbox.manifest
       # 版本更新
       current_version = spec.version
       # 被更新版本记录
       previous_version = sandbox.manifest.version(spec.name)
       # 变动记录
       has_changed_version = current_version != previous_version
       # 找到第一个包含 spec.name 的 Pod，获取对应的 Repo，其实就是 find 方法
       current_repo = analysis_result.specs_by_source.detect { |key, values| break key if values.map(&:name).include?(spec.name) }
       # 获取当前仓库
       current_repo &&= current_repo.url || current_repo.name
       # 获取之前该仓库的信息
       previous_spec_repo = sandbox.manifest.spec_repo(spec.name)
       # 是否仓库有变动
       has_changed_repo = !previous_spec_repo.nil? && current_repo && (current_repo != previous_spec_repo)

       # 通过 title 输出上面的详细变更信息
       title = ...
     else
       # 非 changed 状态，展示 Installing 这个是经常见的 log
       title = "Installing #{spec}"
     end
     UI.titled_section(title.green, title_options) do
       # 通过 name 拿到对应的 installer，记录到 @pod_installers 中
       install_source_of_pod(spec.name)
     end
   else
     # 如果没有 changed 情况，直接展示 Using，也是经常见到的 log
     UI.titled_section("Using #{spec}", title_options) do
       # # 通过 sandbox, specs 的 platform 信息生成 Installer 实例，记录到 @pod_installers 中
       create_pod_installer(spec.name)
     end
   end
 end
end

# 通过缓存返回 PodSourceInstaller 实例
def create_pod_installer(pod_name)
    specs_by_platform = specs_for_pod(pod_name)
 
    # 当通过 pod_name 无法找到对应的 pod_target 或 platform 配置，主动抛出错误信息
    if specs_by_platform.empty?
        requiring_targets = pod_targets.select { |pt| pt.recursive_dependent_targets.any? { |dt| dt.pod_name == pod_name } }
        # message = "..."
        raise StandardError, message
    end
    # 通过 sandbox, specs 的 platform 信息生成 Installer 实例
    pod_installer = PodSourceInstaller.new(sandbox, podfile, specs_by_platform, :can_cache => installation_options.clean?)
    pod_installers << pod_installer
    pod_installer
end

# 如果 resolver 声明一个 Pod 已经安装或者已经存在，将会将其删除并重新安装。如果不存在则直接安装。
def install_source_of_pod(pod_name)
  pod_installer = create_pod_installer(pod_name)
  pod_installer.install!
  @installed_specs.concat(pod_installer.specs_by_platform.values.flatten.uniq)
end

def root_specs
  analysis_result.specifications.map(&:root).uniq
end

def install!
    download_source unless predownloaded? || local?
    PodSourcePreparer.new(root_spec, root).prepare! if local?
    sandbox.remove_local_podspec(name) unless predownloaded? || local? || external?
end

def validate_targets
    validator = Xcode::TargetValidator.new(aggregate_targets, pod_targets, installation_options)
    validator.validate!
end

def validate!
    verify_no_duplicate_framework_and_library_names
    verify_no_static_framework_transitive_dependencies
    verify_swift_pods_swift_version
    verify_swift_pods_have_module_dependencies
    verify_no_multiple_project_names if installation_options.generate_multiple_pod_projects?
end

def integrate
    generate_pods_project
    if installation_options.integrate_targets?
        # 集成用户配置，读取依赖项，使用 xcconfig 来配置
        integrate_user_project
    else
        UI.section 'Skipping User Project Integration'
    end
end

def generate_pods_project
    # 创建 stage sanbox 用于保存安装前的沙盒状态，以支持增量编译的对比
    stage_sandbox(sandbox, pod_targets)
    # 检查是否支持增量编译，如果支持将返回 cache result
    cache_analysis_result = analyze_project_cache
    # 需要重新生成的 target
    pod_targets_to_generate = cache_analysis_result.pod_targets_to_generate
    # 需要重新生成的 aggregate target
    aggregate_targets_to_generate = cache_analysis_result.aggregate_targets_to_generate

    # 清理需要重新生成 target 的 header 和 pod folders
    clean_sandbox(pod_targets_to_generate)
    # 生成 Pod Project，组装 sandbox 中所有 Pod 的 path、build setting、源文件引用、静态库文件、资源文件等
    create_and_save_projects(pod_targets_to_generate, aggregate_targets_to_generate,
                                cache_analysis_result.build_configurations, cache_analysis_result.project_object_version)

    # SandboxDirCleaner 用于清理增量 pod 安装中的无用 headers、target support files 目录
    SandboxDirCleaner.new(sandbox, pod_targets, aggregate_targets).clean!
    # 更新安装后的 cache 结果到目录 `Pods/.project_cache` 下
    update_project_cache(cache_analysis_result, target_installation_results)
end

def perform_post_install_actions
    # 调用 HooksManager 执行每个插件的 post_install 方法 
    run_plugins_post_install_hooks
    # 打印过期 pod target 警告
    warn_for_deprecations
    # 如果 pod 配置了 script phases 脚本，会主动输出一条提示消息
    warn_for_installed_script_phases
    # 输出结束信息 `Pod installation complete!`
    print_post_install_message
end