Use Case

1. Using JSON files as input variables and local variables .
2. Using jsonencode from json template file with the for loop 

Procedure

JSON input variable for all values , prepare files as below and execute :-

• main.tf file :-

variable "json_input" {
  description = "Path to the JSON input file"
  type        = string
}

locals {
  input_data = jsondecode(file(var.json_input))
}

output "name" {
  value = local.input_data.name
}

• test.json file :-

{
    "name": "testname",
    "age": 100,
    "city": "San Francisco"
  }

• • ran terraform apply -var="json_input=test.json" , that took values from json file and worked as expected .

>>>>>

If you want to use json file's input items in for loop, You can use it similar to below example :-

• main.tf file :-

# Define a list of items
variable "items" {
  type    = list(string)
  default = ["Rahul", "Test1", "Test2"]
}

# Render the template
data "template_file" "items_template" {
  template = file("template.tpl")
  vars = {
    items_json = jsonencode([for item in var.items : { name = item }])
  }
}

# Create a local file to save the generated JSON
resource "local_file" "items_json" {
  filename = "items.json"
  content  = data.template_file.items_template.rendered
}

• template.tpl file :-

{
  "items": ${items_json}
}

• This time, inside the vars block, we use a for loop to iterate over each item in the var.items list. In each iteration, we create a map with the key “name” and the value as the current item. This list of maps is then passed to jsonencode to create a JSON array.
• terraform apply

Additional Information

• For additional assistance please contact HashiCorp Support.