Terraform concatenate sublists

This can be achieved easily with combining a splat expression with flatten function:

locals {
  cars = flatten([
    var.users[*].cars
  ])
}

Other solution would be to use a for expression:

locals {
  cars = flatten([
    for user in var.users: user.cars
  ])
}

The result for cars in both cases will be:

cars = [
  "z1",
  "z2",
  "x1",
  "x2",
]

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