Add support for no backend

[Logankwb]

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Description

I'm using CDKTF to produce a Terraform Module for consumption by regular Terraform. As such I'm using cdktf synth to render Terraform JSON code.

This causes some warnings when I go to apply my workspace

For now, I'm working around this by adding an override, but this removes the whole terraform block, which could cause issues if used elsewhere:

stack.AddOverride(jsii.String("terraform"), cdktf.Token_NullValue())

References

[jsteinich]

Related to #1518

If you are using typescript, you may also want to take a look at https://github.com/cdktf/cdktf-tf-module-stack

[marcel-tomate]

I'm encountering a similar issue. I prefer to use an 'empty' http backend, which typically defaults to using environment variables. However, this approach doesn't work with the constructs. I've found a workaround by using: stack.addOverride("terraform.backend", null);. This solution allows me to maintain my own backend.tf file alongside the synthesized one.

[tjholm]

Setting nil does not work for me in AddOverride, nor does setting cdktf.Token_NullValue().

I had to implement an override as a backend implementation (I'm using go).
https://aws.github.io/jsii/user-guides/lib-user/language-specific/go/
Example:

type NilTerraformBackend struct {
	cdktf.TerraformBackend
}

func (t *NilTerraformBackend) ToTerraform() interface{} {
	return map[string]interface{}{}
}

func NewNilTerraformBackend(app constructs.Construct, name *string) *NilTerraformBackend {
	backend := &NilTerraformBackend{}

	cdktf.NewTerraformBackend_Override(backend, app, jsii.String("nil"), name)

	return backend
}

Then create it as part of my stack.

This makes sure the terraform.backend key is never generated in the output.