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SpEL expression failure interpreting dollar sign bracket with Terraform Templates

Issue​

A SpEL expression failure appears while using Terraformer to serialize data from a Terraform Plan execution.  The execution creates a JSON object instead of to a JSON string.The customer pipeline does the following:

  • In the Terraformer Stage, a Terraform Plan outputs a binary object as a Spinnaker Artifact.
  • Terraform shows passing through a plan file which causes Terraform to output a JSON plan file as an output of the stage.The outputted plan file is stored as an artifact that can be used as a tfvars object for the next Terraformer stage.
  • The command toJson is used to ingest the JSON object and transform it into a string.  The string will be passed in via a tfvars object to the subsequent Terraform Apply Stage (with a static/defined by using a module that uploads the tfvars var to a bucket/object)
  • Lastly, the pipeline calls kube to run a 3rd party API to download the object through the name passed to it.

The issue is that if the output has a SpEL escape in it ${ then it fails.

Cause​

The cause is that the SpEL processor in Spinnaker throws a null value if the SpEL expression has ${ in it, and is visible in Spinnaker's code here Also, if the users are using an older Terraform version (< 0.12), then it is also using the template provider from Terraform.The template provider exposes data sources to use templates to generate strings for other Terraform resources or outputs.

❗️ HashiCorp has deprecated the template provider since v0.12