> ## Documentation Index
> Fetch the complete documentation index at: https://errand.nuvrel.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# compact

> Remove empty and null strings from a list.

`compact(list)` returns a new list with all empty string and null elements removed.

## Signature

```
compact(list list(string)) list(string)
```

## Example

Build a list of Docker build arguments, where some are optional. Empty entries are filtered out before the list is joined into a command:

```hcl theme={null}
variable "build_arg_proxy" {
  description = "HTTP proxy for Docker builds (optional)"
  type        = string
  default     = ""
}

variable "build_arg_no_proxy" {
  description = "No-proxy list for Docker builds (optional)"
  type        = string
  default     = ""
}

computed "build_args" {
  description = "Non-empty Docker build arguments"
  expression  = compact([
    var.build_arg_proxy != "" ? "--build-arg HTTP_PROXY=${var.build_arg_proxy}" : "",
    var.build_arg_no_proxy != "" ? "--build-arg NO_PROXY=${var.build_arg_no_proxy}" : "",
  ])
}

task "build" {
  description = "Build the Docker image with optional proxy settings"
  commands    = ["docker build ${join(" ", computed.build_args)} ."]
}
```

When neither proxy variable is set, `computed.build_args` is empty and the command becomes `docker build .`.

## Notes

* `compact` only operates on `list(string)`. It does not apply to lists of other types.
* Use `compact` after producing a list where some elements may be conditionally empty.