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coalesce(vals...) evaluates its arguments in order and returns the first one that is not null.

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Signature

coalesce(vals... any) any
All arguments must have the same type.

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Example

Pick the deployment region from multiple variable sources, falling back through a priority chain: 
variable "target_region" {
  description = "Explicit deployment region (optional)"
  type        = string
  default     = null
}

variable "default_region" {
  description = "Fallback region from team defaults (optional)"
  type        = string
  default     = null
}

computed "region" {
  description = "Resolved deployment region"
  expression  = coalesce(var.target_region, var.default_region, "us-east-1")
}

task "deploy" {
  description = "Deploy to the resolved region"
  commands    = ["aws ecs update-service --region ${computed.region} --cluster prod --service api --force-new-deployment"]
}
If --var target_region=eu-west-1 is passed, that value is used. If only default_region is set, that is used. Otherwise us-east-1 is the fallback.

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Notes

  • coalesce skips null values. It does not skip empty strings, false, or 0.
  • If all arguments are null, coalesce returns an error.
  • coalesce works on scalar values. For picking the first non-empty list, use concat with compact.