Since version 1.58.0 ParameterGroup resources are missing from the generated CloudFormation template.

Reproduction Steps

• Create a new cdk app using version 1.51.0 and add the following code in the stack:

new ParameterGroup(this, "RDS-ParameterGroup", {
  family: "mysql:5.7",
});

• Run the cdk synth command and verify that the AWS::RDS::DBParameterGroup resource exists in the generated CloudFormation template.
• Now update cdk to version 1.58.0 and modify the ParameterGroup to:

new ParameterGroup(this, "RDS-ParameterGroup", {
  engine: DatabaseInstanceEngine.mysql({
    version: MysqlEngineVersion.VER_5_7,
  }),
});

• Run the cdk synth command and view the generated CloudFormation template. The AWS::RDS::DBParameterGroup resource is missing.

What did you expect to happen?

The AWS::RDS::DBParameterGroup resource should exist in both versions of aws cdk.

What actually happened?

The AWS::RDS::DBParameterGroup resource exists in version 1.51.0 but not in 1.58.0.

Environment

• CLI Version: 1.58.0
• Framework Version: 1.58.0
• Node.js Version: 14.5.0
• OS: Windows 10
• Language (Version): TypeScript (3.9.6)

This is 🐛 Bug Report