ability to perform lookups on map fields

[ryane]

It would be useful to be able to perform a key based lookup against a map-type field exposed on a resource. This would be necessary to effectively implement #253. It could also be useful when implementing additional detection options (see #504). For example, I had a situation where I would have liked to have been able to retrieve a particular ip address. Something like: network.interfaces.eth0.ipv4 [1] would have been really helpful.

[1] no idea if this syntax is feasible for a map lookup but hopefully it gets the idea across.

[automaticgiant]

looks like it's close:

param versions {
  default = {
    terraform = "0.11.1"
  }
}

file.fetch terraform {
  source = "https://releases.hashicorp.com/terraform/{{paramMap `versions` | index `terraform`}}/terraform__{{platform.OS}}_amd64.zip"
  destination = "{{param `bin`}}/terraform"
}

2017-12-21T19:37:57Z |ERROR| could not render	component=rpc error=error rendering field source: template: source:1:65: executing "source" at <index `terraform`>: error calling index: cannot index slice/array with type map[string]interface {}: cannot execute template location=build.cvg runID=408f12f9-952f-4e29-b6c3-535588024222
 2017-12-21T19:37:57Z |FATAL| could not get responses	component=client error=error getting status response: rpc error: code = 2 desc = rendering build.cvg: error rendering field source: template: source:1:65: executing "source" at <index `terraform`>: error calling index: cannot index slice/array with type map[string]interface {}: cannot execute template file=build.cvg

it knows i want to index...