从Rails 5.1升级到7.1时出现SassC语法错误

我的应用已从Rails 5.1升级完成，本地服务器基础功能运行正常。运行旧系统测试时（原本想检查paperclip是否失效，最终会切换到Active Storage），推测factory_bot_rails初始化用户时触发了邮件发送，设置headless=false后，浏览器短暂出现以下Sass语法错误：

SassC::SyntaxError in Pages#home
在 /home/dave/bananashack/app/views/user_mailer/welcome_email.html.erb 中触发错误：

错误："calc(100vh - 110px)" 不是 `min` 函数可用的数值类型
        在 stdin 的第1行第33074列，`min` 函数内
        来自 stdin 的第1行第33074列
>> x;flex:1;flex-direction:column;max-height:min(650px,calc(100vh - 110px));ove
   ------------------------------------------^

提取的相关代码（第50行附近）：
48    line = Native.context_get_error_line(context)
49
50    raise SyntaxError.new(message, filename: filename, line: line)
51  end
52
53  css = Native.context_get_output_string(context)
              
提示：你可以在Gemfile中添加 gem 'error_highlight', '>= 0.4.0'，它会显示更精确的错误位置。

Rails根目录: /home/dave/bananashack

应用调用栈 | 框架调用栈 | 完整调用栈
sassc (2.4.0) lib/sassc/engine.rb:50:in `render'
sassc-rails (2.1.2) lib/sassc/rails/compressor.rb:29:in `call'
sprockets (4.2.1) lib/sprockets/sass_compressor.rb:30:in `call'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:84:in `call_processor'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:66:in `block in call_processors'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:65:in `reverse_each'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:65:in `call_processors'
sprockets (4.2.1) lib/sprockets/loader.rb:184:in `load_from_unloaded'
sprockets (4.2.1) lib/sprockets/loader.rb:59:in `block in load'
sprockets (4.2.1) lib/sprockets/loader.rb:339:in `fetch_asset_from_dependency_cache'
sprockets (4.2.1) lib/sprockets/loader.rb:43:in `load'
sprockets (4.2.1) lib/sprockets/cached_environment.rb:44:in `block in load'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/map.rb:207:in `block in fetch_or_store'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/map.rb:187:in `fetch'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/map.rb:206:in `fetch_or_store'
sprockets (4.2.1) lib/sprockets/cached_environment.rb:44:in `load'
sprockets (4.2.1) lib/sprockets/bundle.rb:32:in `block in call'
/home/dave/.rbenv/versions/3.1.4/lib/ruby/3.1.0/set.rb:511:in `each_key'
/home/dave/.rbenv/versions/3.1.4/lib/ruby/3.1.0/set.rb:511:in `each'
sprockets (4.2.1) lib/sprockets/bundle.rb:31:in `call'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:84:in `call_processor'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:66:in `block in call_processors'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:65:in `reverse_each'
sprockets (4.2.1) lib/sprockets/processor_utils.rb:65:in `call_processors'
sprockets (4.2.1) lib/sprockets/loader.rb:184:in `load_from_unloaded'
sprockets (4.2.1) lib/sprockets/loader.rb:59:in `block in load'
sprockets (4.2.1) lib/sprockets/loader.rb:339:in `fetch_asset_from_dependency_cache'
sprockets (4.2.1) lib/sprockets/loader.rb:43:in `load'
sprockets (4.2.1) lib/sprockets/cached_environment.rb:44:in `block in load'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/map.rb:207:in `block in fetch_or_store'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/map.rb:187:in `fetch'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/map.rb:206:in `fetch_or_store'
sprockets (4.2.1) lib/sprockets/cached_environment.rb:44:in `load'
sprockets (4.2.1) lib/sprockets/base.rb:81:in `find_asset'
sprockets (4.2.1) lib/sprockets/base.rb:88:in `find_all_linked_assets'
sprockets (4.2.1) lib/sprockets/manifest.rb:125:in `each'
sprockets (4.2.1) lib/sprockets/manifest.rb:125:in `to_a'
sprockets (4.2.1) lib/sprockets/manifest.rb:125:in `block (2 levels) in find'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/safe_task_executor.rb:24:in `block in execute'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/synchronization/mutex_lockable_object.rb:48:in `block in synchronize'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/synchronization/mutex_lockable_object.rb:48:in `synchronize'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/synchronization/mutex_lockable_object.rb:48:in `synchronize'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/safe_task_executor.rb:22:in `execute'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/promise.rb:564:in `block in realize'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/ruby_thread_pool_executor.rb:359:in `run_task'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/ruby_thread_pool_executor.rb:350:in `block (3 levels) in create_worker'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/ruby_thread_pool_executor.rb:341:in `loop'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/ruby_thread_pool_executor.rb:341:in `block (2 levels) in create_worker'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/ruby_thread_pool_executor.rb:340:in `catch'
concurrent-ruby (1.3.3) lib/concurrent-ruby/concurrent/executor/ruby_thread_pool_executor.rb:340:in `block in create_worker'

问题原因 #

你使用的sassc版本（2.4.0）基于旧版LibSass，不支持在min()函数中直接传入calc()表达式——它要求min()的参数必须是纯数值，不能包含动态计算逻辑。

解决方法 #

1. 升级sassc依赖
   在Gemfile中更新sassc到3.0及以上版本，运行bundle update sassc。新版会自动将Sass的min()编译为CSS原生min()，原生CSS支持calc()作为参数。

2. 兼容写法替换
   如果暂时无法升级依赖，可把出错的代码替换为Sass兼容的逻辑：

   max-height: if(100vh - 110px > 650px, 650px, calc(100vh - 110px));
   

   或者用CSS变量先存储计算值：

   --container-max-height: calc(100vh - 110px);
   max-height: min(650px, var(--container-max-height));
   

3. 测试场景临时规避
   如果你只是为了测试paperclip功能，可直接在测试环境禁用邮件发送，避免触发模板编译错误。在config/environments/test.rb中添加：

   config.action_mailer.perform_deliveries = false
   

内容的提问来源于stack exchange，提问作者daveasdf_2