如何基于环境配置Middleman的s3_sync参数 解决未定义变量报错

错误原因 #

报错是两个配置问题共同导致的：

1. 配置顺序颠倒：configure :internal 块执行在 activate :s3_sync 之前，此时s3_sync插件还未被初始化，自然不存在s3_sync这个对象
2. 环境配置块内的调用方式错误：在configure块中不能直接使用s3_sync变量，需要通过全局config对象访问已激活的插件配置

修复方案 #

方案1：拆分通用配置和环境配置（适合多环境差异参数多的场景）

调整配置顺序，先激活插件写通用配置，再用环境块覆盖差异参数，修改后的config.rb如下：

# 先激活s3_sync插件，写入所有环境通用的配置
activate :s3_sync do |s3_sync|
  s3_sync.bucket                     = ENV['DOCS_AWS_BUCKET'] # 默认公网文档桶
  s3_sync.region                     = ENV['DOCS_AWS_REGION']
  s3_sync.aws_access_key_id          = ENV['DOCS_AWS_ACCESS_KEY_ID']
  s3_sync.aws_secret_access_key      = ENV['DOCS_AWS_SECRET_ACCESS_KEY']
  s3_sync.prefer_gzip                = true
  s3_sync.path_style                 = true
  s3_sync.reduced_redundancy_storage = false
  s3_sync.acl                        = 'public-read'
  s3_sync.encryption                 = false
  s3_sync.prefix                     = ''
  s3_sync.version_bucket             = false
  s3_sync.index_document             = 'index.html'
  s3_sync.error_document             = '404.html'
end

# 再定义internal环境的专属配置，覆盖需要差异化的参数
configure :internal do
  config[:s3_sync].bucket = ENV['INTERNAL_DOCS_AWS_BUCKET']
  # 如果内部桶的区域、密钥也不同，可在此处追加覆盖
  # config[:s3_sync].region = ENV['INTERNAL_DOCS_AWS_REGION']
  # config[:s3_sync].aws_access_key_id = ENV['INTERNAL_DOCS_AWS_ACCESS_KEY_ID']
  # config[:s3_sync].aws_secret_access_key = ENV['INTERNAL_DOCS_AWS_SECRET_ACCESS_KEY']
end

方案2：激活时直接判断环境（适合差异参数少的场景）

直接在插件激活块内判断当前运行环境，动态赋值参数，写法更简洁：

activate :s3_sync do |s3_sync|
  # 按环境动态选择对应存储桶
  s3_sync.bucket = if environment == :internal
    ENV['INTERNAL_DOCS_AWS_BUCKET']
  else
    ENV['DOCS_AWS_BUCKET']
  end
  # 其余通用配置保持原有内容不变
  s3_sync.region                     = ENV['DOCS_AWS_REGION']
  s3_sync.aws_access_key_id          = ENV['DOCS_AWS_ACCESS_KEY_ID']
  s3_sync.aws_secret_access_key      = ENV['DOCS_AWS_SECRET_ACCESS_KEY']
  s3_sync.prefer_gzip                = true
  s3_sync.path_style                 = true
  s3_sync.reduced_redundancy_storage = false
  s3_sync.acl                        = 'public-read'
  s3_sync.encryption                 = false
  s3_sync.prefix                     = ''
  s3_sync.version_bucket             = false
  s3_sync.index_document             = 'index.html'
  s3_sync.error_document             = '404.html'
end

验证 #

配置修改完成后，再执行原来的推送命令即可正常按环境对应存储桶推送：
bundle exec middleman s3_sync --verbose --environment=internal

内容的提问来源于stack exchange，提问作者Underoos