cdk synth does not include the metadata in the json generated file

When running cdk synth MyStackName CDKMetadata are shown but not included in the template.json generated file.

We have a simple stack containing 3 parameters and 3 outputs, with no resource. cdk deploy MyStackName works fine

But in a pipeline, CodeBuild will generate the template.json without any resource. Then the CloudFormation action will generate a ValidationException : "errorMessage": "Template format error: At least one Resources member must be defined."

Expected behavior We expect to have the same behavior as cdk deploy command which use the yaml generated template because, in the following template, there is a Resource:

Parameters:
  sdgDomainNameParam:
    Type: String
  sdgDomainCertificateArnParam:
    Type: String
  destinationEnvironmentParam:
    Type: String
Outputs:
  sdgDomainName:
    Description: Domain Name
    Value:
      Ref: sdgDomainNameParam
    Export:
      Name: sdgDomainName
  sdgDomainCertificateArn:
    Description: Domain Certificate Arn
    Value:
      Ref: sdgDomainCertificateArnParam
    Export:
      Name: sdgDomainCertificateArn
  destinationEnvironment:
    Description: destination Environment
    Value:
      Ref: destinationEnvironmentParam
    Export:
      Name: destinationEnvironment
Resources:
  CDKMetadata:
    Type: AWS::CDK::Metadata
    Properties:
      Modules: aws-cdk=1.34.1,@aws-cdk/assets=1.34.1,@aws-cdk/aws-apigateway=1.34.1,@aws-cdk/aws-applicationautoscaling=1.34.1,@aws-cdk/aws-autoscaling-common=1.34.1,@aws-cdk/aws-certificatemanager=1.34.1,@aws-cdk/aws-cloudformation=1.34.1,@aws-cdk/aws-cloudfront=1.34.1,@aws-cdk/aws-cloudwatch=1.34.1,@aws-cdk/aws-cognito=1.34.1,@aws-cdk/aws-dynamodb=1.34.1,@aws-cdk/aws-ec2=1.34.1,@aws-cdk/aws-events=1.34.1,@aws-cdk/aws-iam=1.34.1,@aws-cdk/aws-kms=1.34.1,@aws-cdk/aws-lambda=1.34.1,@aws-cdk/aws-logs=1.34.1,@aws-cdk/aws-s3=1.34.1,@aws-cdk/aws-s3-assets=1.34.1,@aws-cdk/aws-sqs=1.34.1,@aws-cdk/aws-ssm=1.34.1,@aws-cdk/cloud-assembly-schema=1.34.1,@aws-cdk/core=1.34.1,@aws-cdk/custom-resources=1.34.1,@aws-cdk/cx-api=1.34.1,@aws-cdk/region-info=1.34.1,jsii-runtime=node.js/v12.14.1
    Condition: CDKMetadataAvailable
Conditions:
  CDKMetadataAvailable:
    Fn::Or:
      - Fn::Or:
          - Fn::Equals:
              - Ref: AWS::Region
              - ap-east-1
          - Fn::Equals:
              - Ref: AWS::Region
              - ap-northeast-1
          - Fn::Equals:
              - Ref: AWS::Region
              - ap-northeast-2
          - Fn::Equals:
              - Ref: AWS::Region
              - ap-south-1
          - Fn::Equals:
              - Ref: AWS::Region
              - ap-southeast-1
          - Fn::Equals:
              - Ref: AWS::Region
              - ap-southeast-2
          - Fn::Equals:
              - Ref: AWS::Region
              - ca-central-1
          - Fn::Equals:
              - Ref: AWS::Region
              - cn-north-1
          - Fn::Equals:
              - Ref: AWS::Region
              - cn-northwest-1
          - Fn::Equals:
              - Ref: AWS::Region
              - eu-central-1
      - Fn::Or:
          - Fn::Equals:
              - Ref: AWS::Region
              - eu-north-1
          - Fn::Equals:
              - Ref: AWS::Region
              - eu-west-1
          - Fn::Equals:
              - Ref: AWS::Region
              - eu-west-2
          - Fn::Equals:
              - Ref: AWS::Region
              - eu-west-3
          - Fn::Equals:
              - Ref: AWS::Region
              - me-south-1
          - Fn::Equals:
              - Ref: AWS::Region
              - sa-east-1
          - Fn::Equals:
              - Ref: AWS::Region
              - us-east-1
          - Fn::Equals:
              - Ref: AWS::Region
              - us-east-2
          - Fn::Equals:
              - Ref: AWS::Region
              - us-west-1
          - Fn::Equals:
              - Ref: AWS::Region
              - us-west-2`

Code Snippet

        const sdgDomainName = new CfnParameter(this, 'sdgDomainNameParam').value.toString();
        const sdgDomainCertificateArn = new CfnParameter(this, 'sdgDomainCertificateArnParam').value.toString();
        const sdgDestinationEnvironment = new CfnParameter(this, 'destinationEnvironmentParam').value.toString();

        new CfnOutput(this, "sdgDomainName", {
            description: "Domain Name",
            exportName: 'sdgDomainName',
            value: sdgDomainName
        });

        new CfnOutput(this, "sdgDomainCertificateArn", {
            description: "Domain Certificate Arn",
            exportName: 'sdgDomainCertificateArn',
            value: sdgDomainCertificateArn
        });

        new CfnOutput(this, "destinationEnvironment", {
            description: "destination Environment",
            exportName: 'destinationEnvironment',
            value: sdgDestinationEnvironment
        });

Generated template

{
  "Parameters": {
    "sdgDomainNameParam": {
      "Type": "String"
    },
    "sdgDomainCertificateArnParam": {
      "Type": "String"
    },
    "destinationEnvironmentParam": {
      "Type": "String"
    }
  },
  "Outputs": {
    "sdgDomainName": {
      "Description": "Domain Name",
      "Value": {
        "Ref": "sdgDomainNameParam"
      },
      "Export": {
        "Name": "sdgDomainName"
      }
    },
    "sdgDomainCertificateArn": {
      "Description": "Domain Certificate Arn",
      "Value": {
        "Ref": "sdgDomainCertificateArnParam"
      },
      "Export": {
        "Name": "sdgDomainCertificateArn"
      }
    },
    "destinationEnvironment": {
      "Description": "destination Environment",
      "Value": {
        "Ref": "destinationEnvironmentParam"
      },
      "Export": {
        "Name": "destinationEnvironment"
      }
    }
  }
}

[shivlaks]

@gyurist thanks for that information. I’ll have a look at the logic but I’m bumping this up to a p1.

The behaviour should be consistent regardless of template size.

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