Variable Type Validation object() does not report location

[damon-atkins]

Terraform Version

Terraform v0.13.5

Terraform Configuration Files

variables.tf

variable foo {
   type = map(object({
       abc = bool
   }))

  default = {
    "memap" = {
       abc = "i am a string"
       iamme = "one two three"
    }
  }
}

Expected Behavior

The environment variable TF_VAR_foo does not contain a valid value for
variable "foo" -> "memap" -> "abc" : a bool is required.

Error: Invalid default value for variable

  on variables.tf line 8, in variable "foo":
   8:   default = {
   9:     "memap" = {
  10:        abc = "i am a string"
  11:        iamme = "one two three"
  12:     }
  13:   }

This default value is not compatible with the variable's type constraint: a
bool is required within "foo" -> "memap" -> "abc".

Actual Behavior

The environment variable TF_VAR_foo does not contain a valid value for
variable "foo": a bool is required.

Error: Invalid default value for variable

  on variables.tf line 8, in variable "foo":
   8:   default = {
   9:     "memap" = {
  10:        abc = "i am a string"
  11:        iamme = "one two three"
  12:     }
  13:   }

This default value is not compatible with the variable's type constraint: a
bool is required.

Steps to Reproduce

Please list the full steps required to reproduce the issue, for example:

1. terraform init
2. terraform apply

[apparentlymart]

Thanks for reporting this, @damon-atkins!

I believe cause of this bug is here:

terraform/configs/named_values.go

Lines 119 to 124 in d390fad

	diags = append(diags, &hcl.Diagnostic{
	Severity: hcl.DiagError,
	Summary: "Invalid default value for variable",
	Detail: fmt.Sprintf("This default value is not compatible with the variable's type constraint: %s.", err),
	Subject: attr.Expr.Range().Ptr(),
	})

Just returning err directly here produces only the error message and not the context, because the subsystem that is generating this particular error doesn't know how to write context in Terraform language syntax (it's at a lower layer of abstraction). However, Terraform has a helper function tfdiags.FormatError which knows how to add that extra context in a Terraform-language-like way, so I expect the solution here would be to replace the direct err with a call to tfdiags.FormatError(err), which should make the output look something like this:

Error: Invalid default value for variable

  on variables.tf line 8, in variable "foo":
   8:   default = {
   9:     "memap" = {
  10:        abc = "i am a string"
  11:        iamme = "one two three"
  12:     }
  13:   }

This default value is not compatible with the variable's type constraint:
.memap.abc: a bool is required.

[github-actions]

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