Allow outputting additional TF outputs

Author: bastjan

class/defaults.yml

@@ -12,6 +12,7 @@ parameters:
       git: {}
     provider: ${facts:cloud}
     version: ${openshift4_terraform:_tf_module_version:${openshift4_terraform:provider}}
+    additional_outputs: {}
     terraform_variables:
       source: git::https://github.com/appuio/terraform-openshift4-${openshift4_terraform:provider}.git//?ref=${openshift4_terraform:version}
       cluster_id: ${cluster:name}

component/main.jsonnet

@@ -74,12 +74,13 @@ local terraform_config =
         },
       },
     },
+    local mergedOutputs = params.additional_outputs + outputs[params.provider],
     'outputs.tf': {
       output: {
         [out]: {
-          value: outputs[params.provider][out],
+          value: mergedOutputs[out],
         }
-        for out in std.objectFields(outputs[params.provider])
+        for out in std.objectFields(mergedOutputs)
       },
     },
     'variables.tf': {

docs/modules/ROOT/pages/references/parameters.adoc

@@ -62,6 +62,26 @@ Terraform input variables for the selected Terraform module (see parameter `prov
 They're passed to the module without any further processing.
 The variables are merged with the defaults, unless overridden.
 
+
+== `additional_outputs`
+
+[horizontal]
+type:: object
+default:: `{}`
+example::
++
+[source,yaml]
+----
+additional_outputs:
+  my_output: '\${module.cluster.my_output}'
+----
+
+Additional outputs that are passed to the Terraform module.
+The outputs are merged with the defaults, defaults can't be overridden.
+The keys are then name of the output, the value should contain a reference to a output variable from the Terraform module.
+Additional escaping might be needed since Terraform variables use the same syntax as reclass; see the example above.
+
+
 == `version`
 
 [horizontal]

tests/cloudscale.yml

@@ -14,3 +14,5 @@ parameters:
         - ssh-ed25519 AA...
       control_vshn_net_token: asdf...
       hieradata_repo_user: project_123_bot
+    additional_outputs:
+      region: '\${module.cluster.region}'

tests/golden/cloudscale/openshift4-terraform/openshift4-terraform/outputs.tf.json

@@ -5,6 +5,9 @@
     },
     "hieradata_mr": {
       "value": "${module.cluster.hieradata_mr}"
+    },
+    "region": {
+      "value": "${module.cluster.region}"
     }
   }
 }