Terraform merge list of maps - list

Question

My input is as below:
list_groups = [
{
dev-api = {
envs = [
"dev-eu-1",
"dev-eu-2",
]
hosts = [
"dev-api-eu1",
"dev-api-eu2",
]
}
},
{
dev-api = {
envs = [
"dev-us-1",
"dev-us-2",
]
hosts = [
"dev-api-us1",
"dev-api-us2",
]
}
},
]
I am using merge as below:
output "map_groups" {
value = merge(var.list_groups...)
}
And the output I get is :
map_groups = {
dev-api = {
envs = [
"dev-us-1",
"dev-us-2",
]
hosts = [
"dev-api-us1",
"dev-api-us2",
]
}
}
But I need the output to be:
map_groups = {
dev-api = {
envs = [
"dev-us-1",
"dev-us-2",
"dev-eu-1",
"dev-eu-2"
]
hosts = [
"dev-api-us1",
"dev-api-us2",
"dev-api-eu1",
"dev-api-eu2"
]
}
}
I understand the merge is eating up one of the entries because the key is the same but if it could somehow merge the entries/elements, that'll be great.

Answer 1

This is a rather complex issue. I think you should concentrate on simplifying your input data, rather than trying to come out with some convoluted TF code to post-fix your input data structures.
Nevertheless, the expansion symbol ... can be used to solve the issue in terraform.
variable "list_groups" {
default = [
{
dev-api = {
envs = [
"dev-eu-1",
"dev-eu-2",
]
hosts = [
"dev-api-eu1",
"dev-api-eu2",
]
}
},
{
dev-api = {
envs = [
"dev-us-1",
"dev-us-2",
]
hosts = [
"dev-api-us1",
"dev-api-us2",
]
}
},
]
}
locals {
api_names = distinct([for api in var.list_groups: keys(api)[0]])
}
output "test" {
value = {
for key, val in {
for api_name in local.api_names:
api_name => {
envs = flatten([
for api in var.list_groups:
api[api_name].envs
])
hosts = flatten([
for api in var.list_groups:
api[api_name].hosts
])
}...
}:
key => val[0]
}
}
Output is:
test = {
"dev-api" = {
"envs" = [
"dev-eu-1",
"dev-eu-2",
"dev-us-1",
"dev-us-2",
]
"hosts" = [
"dev-api-eu1",
"dev-api-eu2",
"dev-api-us1",
"dev-api-us2",
]
}
}