Remove a map item in terraform

output "product" {
value = compact([for x in distinct(yamldecode(file("resource/lab/abc.yaml"))["account_list"]["resource_tags"][*]["TAG:product"]) : x == "fargate" ? "" : x])

}

I get this output:

• test = [
  • "enter", ]

compact function solved the problem.

The Terraform language is based on functional principles rather than imperative principles and so it does not support directly modifying an existing data structure. Instead, the best way to think about goals like this is how to define a new value which differs from your existing value in some particular way.

For collection and structural types, the most common way to derive a new value with different elements is to use a for expression, which describes a rule for creating a new collection based on the elements of an existing collection. For each element in the source collection we can decide whether to use it in the result at all, and then if we do decide to use it we can also describe how to calculate a new element value based on the input element value.

In your case you seem to want to create a new list with fewer elements than an existing list. (Your question title mentions maps, but the question text shows a tuple which is behaving as a list.)

To produce a new collection with fewer elements we use the optional if clause of a for expression. For example:

[for x in var.example : x if x != "fargate"]

In the above expression, x refers to each element of var.example in turn. Terraform first evaluates the if clause, and expects it to return true if the element should be used. If so, it will then evaluate the expression immediately after the colon, which in this case is just x and so the result element is identical to the input element.

Your example expression also includes some unrelated work to decode a YAML string and then traverse to the list inside it. That expression replaces var.example in the above expression, as follows:

output "products" {
  value = toset([
    for x in yamldecode(file("${path.module}/resource/lab/abc.yaml"))["account_list"]["resource_tags"][*]["TAG:product"]: x
    if x != "fargate"
  ])
}

I made some other small changes to the above compared to your example:

• I named the output value "products" instead of "product", because it's returning a collection and it's Terraform language idiom to use plural names for collection values.

• I wrapped the expression in toset instead of distinct, because from your description it seems like this is an unordered collection of unique strings rather than an ordered sequence of strings.

• I added path.module to the front of the file path so that this will look for the file in the current module directory. If your output value is currently in a root module then this doesn't really matter because the module directory will always be the current working directory, but it's good practice to include this so that it's clear that the file belongs to the module.

  Therefore returning a set is more appropriate than returning a list because it communicates to the caller of the module that they may not rely on the order of these items, and therefore allows the order to potentially change in future without it being a breaking change to your module.