如何在AWS CloudFormation中向嵌套堆栈传递CommaDelimitedList参数

问题场景 #

在AWS CloudFormation中从父模板调用子模块时，触发错误：

"Value of property Parameters must be an object with String (or simple type) properties"

父模板（Parent.yml） #

AWSTemplateFormatVersion: '2010-09-09'
Parameters:
  DirsToCreate:
    Type: List<String>
    Default: "test/injury_code,testing/cmd_injury_code,upload/exclusion"
    Description: "Comma delimited directories to create."

  ExportedSecretValue:
    Type: String
    Description: Glue Data Load db user's credential

  dataLoadType:
    Type: String
    Default: icd
    Description: Specify the type of data load

  prefix:
    Type: String
    Default: test/checking
    Description: S3 Key value 

Resources:
  IcdData:
    Type: VN::Glue::Test::MODULE
    Properties:
      DirsToCreate: !Join
        - ','
        - !Ref DirsToCreate
      dataLoadType: !Ref dataLoadType
      prefix: !Ref prefix
      ExportedSecretValue: !Ref ExportedSecretValue

嵌套堆栈模板（Nested-stack.yml） #

AWSTemplateFormatVersion: '2010-09-09'
Parameters:
  DirsToCreate:
    Type: CommaDelimitedList
    Description: "Comma delimited list of directories to create."

  dataLoadType:
    Type: String
    Description: Specify the type of data load ICD or DCD

  prefix:
    Type: String
    Description: S3 Key value for ICD or DCD

  ExportedSecretValue:
    Type: String
    Description: Glue Data Load db user's credential

Resources:
 S3CustomResource:
   Type: Custom::S3CustomResource
   Properties:
     ServiceToken: !GetAtt CreateS3FoldersLambda.Arn
     the_bucket: !Ref DataS3Bucket
     dirs_to_create: !Ref DirsToCreate

错误原因 #

父模板中DirsToCreate参数类型为List<String>，通过!Join拼接成字符串后传递给子模板，但子模板期望接收CommaDelimitedList类型参数。CloudFormation要求传递给嵌套模块的参数必须是字符串或简单类型，这种类型不匹配导致了错误。

解决方案 #

方案1：统一参数类型，直接传递列表引用 #

将父模板的DirsToCreate参数类型改为CommaDelimitedList，与子模板保持一致，直接传递原始引用无需拼接：

# 父模板修改后的参数与资源部分
Parameters:
  DirsToCreate:
    Type: CommaDelimitedList
    Default: "test/injury_code,testing/cmd_injury_code,upload/exclusion"
    Description: "Comma delimited directories to create."

Resources:
  IcdData:
    Type: VN::Glue::Test::MODULE
    Properties:
      DirsToCreate: !Ref DirsToCreate
      dataLoadType: !Ref dataLoadType
      prefix: !Ref prefix
      ExportedSecretValue: !Ref ExportedSecretValue

方案2：保留父模板类型，调整子模板接收逻辑 #

如果必须保留父模板的List<String>类型，可将子模板的DirsToCreate改为String类型，接收拼接后的字符串，再在子模板内部拆分为列表：

# 子模板修改后的参数部分
Parameters:
  DirsToCreate:
    Type: String
    Description: "Comma delimited list of directories to create."

# 子模板自定义资源部分修改
Resources:
 S3CustomResource:
   Type: Custom::S3CustomResource
   Properties:
     ServiceToken: !GetAtt CreateS3FoldersLambda.Arn
     the_bucket: !Ref DataS3Bucket
     dirs_to_create: !Split [",", !Ref DirsToCreate]

内容的提问来源于stack exchange，提问作者gcpdev-guy