no_error_checking.md

Why no error checking?

Terrascript does not perform any error checking whatsoever! This was a deliberate design decision to keep the code simple. Therefore it is perfectly possible to generate JSON output that Terraform will later reject.

from terrascript import dump, function
from terrascript.aws.r import aws_instance

aws_instance('myinstance', foo=function.bar('hello world'))

print(dump())

Terraform will reject the generated JSON as the aws_instance resource does not accept a foo argument and there is also no function bar().

{
  "resource": {
    "aws_instance": {
      "myinstance": {
        "foo": "${bar(\"hello world\")}"
      }
    }
  }
}

At an early stage I contemplated parsing the Terraform Go source code and auto-create Python code that does indeed verify whether the generated JSON configuration is valid Terraform input. This attempt proved way to difficult so I abandonded that approach.