Maps not coerced to objects for input variables

[davecardwell]

Terraform Version

Terraform v0.12.20

Terraform Configuration Files

main.tf

module "child" {
  source = "./child"
  foo    = map("bar", "baz")
}

child/child.tf

variable "foo" {
  type = object({ bar = string })
}

Debug Output

https://gist.github.com/davecardwell/94c238e4f12d7d5612668a3747a35ea1

Expected Behavior

From Conversion of Complex Types in the docs I expected the map to be converted to an object and accepted as a valid value.

Actual Behavior

Error: Invalid value for module argument

  on main.tf line 3, in module "child":
   3:   foo    = map("bar", "baz")

The given value is not suitable for child module variable "foo" defined at
child/child.tf:1,1-15: object required.

Steps to Reproduce

1. terraform init
2. terraform validate

[jbardin]

Hi @davecardwell,

Thanks, it appears the conversion functions aren't handling this case correctly.

The good news is that if you're only dealing with literals or expressions, they will initially be typed as an object and pass through. The map function itself is deprecated and should not be used.

[davecardwell]

Thanks for the speedy response, @jbardin.

I used the map function in my example but my actual use case is passing the result of an External Data Source to a child module.

I can set the variable type as map(string) and it works fine, or I can choose the individual values from the data source to pass through in the module {} block, so there are workarounds.

I went digging and raised the issue withgo-cty so will see if they think it’s viable to support map-to-object conversions. I don’t mind if you want to close this issue or leave it open for tracking progress there.

[ghost]

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