This code is written in the HashiCorp Configuration Language (HCL),...

This code is written in the HashiCorp Configuration Language (HCL), commonly used in Terraform. Let’s break down what it does:

1. Definition of a dynamic block: The dynamic block in HCL dynamically generates nested configuration blocks based on a condition or a collection. Here, the dynamic block is named default.

2. Iteration with for_each: The for_each argument specifies the list over which the dynamic block will iterate. In this specific case:

   • column.value.default != null ? [column.value.default] : []: It checks if column.value.default is not null. If it’s not null, a list containing column.value.default is created ([column.value.default]). If it’s null, an empty list ([]) is used.

     This means the dynamic "default" block will only be included in the rendered configuration if column.value.default is not null.

3. Contents of the dynamic block: Within the content block, it defines two attributes, constant and expression, and assigns values to them using try():

   • constant = try(default.value.constant, null): The try() function attempts to evaluate default.value.constant. If it fails (for instance, if default.value.constant is missing or does not exist), it assigns null.
   • expression = try(default.value.expression, null): Similarly, this tries to evaluate default.value.expression and assigns null if it fails.

Overall Behavior:

• If column.value.default is not null, the code creates a default block. Inside this block:
  • The constant attribute gets the value of default.value.constant (or null if it doesn’t exist).
  • The expression attribute gets the value of default.value.expression (or null if it doesn’t exist).
• If column.value.default is null, no default block is created.

This pattern is commonly used in Terraform for conditional and dynamic resource creation.