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The assert block

Use the assert block to allow code generation when a condition is true. It helps to catch mistakes in your configuration. You can use the assert block only when the generation context is of type stack. The assert block behaves hierarchically, meaning any assert blocks defined in a parent directory will apply to all stacks within that directory. For example, an assert block defined at the root of a project will apply to all stacks.

You can define assert blocks inside generate_hcl and generate_file blocks, where the assert block can access locally scoped data like the let namespace.


assertionbooleanany expression which results in a boolean
messagestringerror message that must evaluate as string
warning (optional)booleanboolean attribute, defaults to false

The assertion condition gets checked within the context of a stack. If it is false, no code gets generated for that stack, and an error appears in the message field.

To still generate code for a stack when the assertion is false, set the optional warning field to true. This setting will produce a warning message along with the generated code.


    assertion = <expression evaluating to boolean>
    message = "assertion failure reason"


assert {
  assertion = global.a == global.b
  message   = "assertion failed, details: ${global.a} != ${global.b}"