apparentlymart
commented
1 year ago Hi @mforeman19! Thanks for reporting this.
Looking at this part of your example:
concat(local.list_object_a, local.list_object_b) These two lists seem to have different element types, so they cannot be concatenated together into a single list with a single element type. Looking at today's implementation of concat I see that it does try to return a list, but it can do so only if all of the given lists have compatible element types.
Your example with list_of_objects_ternary_with_tolist seems to confirm that's what's going on, because tolist uses the same logic to try to determine a common element type as concat does. The difference is just that concat falls back on creating a tuple if it cannot create a list, whereas tolist has no option but to fail because it would be invalid for it to return a non-list type.
I expect this would work if you made the two lists have unifyable object types, so that Terraform can find a suitable single object type to use as the type of the resulting list:
locals {
list_object_a_enabled = true
list_object_a = tolist([
{
id = "a"
enabled = true
expiration = null
nested = {
nested_id = 0
nested_class = "test"
}
}
])
list_object_b = tolist([
{
id = "b"
enabled = true
expiration = { days = 31 }
nested = null
}
])
list_of_objects_ternary = local.list_object_a_enabled == true ? concat(local.list_object_a, local.list_object_b) : local.list_object_b
list_of_objects_ternary_with_tolist = local.list_object_a_enabled == true ? tolist(concat(local.list_object_a, local.list_object_b)) : local.list_object_b
list_of_objects_ternary_false = local.list_object_a_enabled == false ? concat(local.list_object_a, local.list_object_b) : local.list_object_b
}The extra null attributes I added above should allow Terraform to determine that the result type of concat would be the following list type, after noticing that null is a valid value of any type:
list(object({
id = string
enabled = bool
expiration = object({
days = number
})
nested = object({
nested_id = number
nested_class = test
})
}))Can you give that variant a try and see if you get the behavior you wanted?
mforeman19
jay-laitmatus
crw
adamretter
kbcz1989
haskovec
inshaffff
ChristofferWin
Terraform Version
Terraform Configuration Files
Debug Output
Expected Behavior
If I concat lists, I expect a list to be returned, not a tuple. This seems to result from complex objects (like nested maps) being involved in the concatenation. I haven't noticed this if the lists contained string or bool or int. Perhaps this has already been found or the behavior is expected.
Actual Behavior
See errors
Steps to Reproduce
Attempt to concat two lists that contain complex objects (like a map)
Additional Context
It'd be useful to concat these types of objects together, particularly in use for modules. I have lists containing complex object variables I'm trying to pass into modules and then perform some modifications on top of those variables if certain conditions are met. Sometimes these variables have a certain nested map in them, sometimes they don't. Sometimes it might just be string fields instead of string fields + map objects within an object in the list.
References
No response