[Stacktrace] - Call to function "compact" failed: panic in function implementation: value is null #21548
Comments
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Hi @karl-tpio ! Thank you for opening this issue. The panic you've reported is now fixed, terraform instead provides an error message: Here's a very silly example that illustrates using variable "list" {
default = null
type = list(string)
}
output example {
value = var.list != null ? compact(var.list) : ["it's null"]
}terraform apply
Apply complete! Resources: 0 added, 0 changed, 0 destroyed.
Outputs:
example = [
"it's null",
]I doubt that example is enough to fully answer your secondary question about conditionally creating a resource. For that, I recommend you visit the community forum where there are far more people ready to help, whereas the GitHub issues here are generally monitored only by our few core maintainers. |
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I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues. If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further. |
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Hi. I know why this specific exception is happening. I am creating this ticket to:
Document a case that currently generates a fatal stack trace but should probably be something that can be handled more gracefully... like how TF .12 currently handles lots of other errors
to ask for a "smarter" way to conditionally create a resource.
Terraform Version
Terraform Configuration Files
There are a few things at play here. The crash is coming from this resource:
The crash is coming from this line:
The
aws_security_group_rule.filebeat_ingress_cidr_6resource is inside a module that can be configured with this variable:The
filebeat_ingress_ipv6_cidrsvariable is set like this in the module caller/consumer:Critically, here's what the
data.aws_vpc.some_vpcresource hasNote there is no defined
ipv6_cidr_blockattribute on the data resource. This is because the VPC ID that the data block is "resolving" does not have IPv6 enabled.Debug Output
I will happily provide this if it's deemed necessary.
Crash Output
Expected Behavior
I was expecting a "safe" error with a terraform provided message about one the function arguments being
null.Actual Behavior
I received a stack trace.
Steps to Reproduce
Please see the above code snippets.
A variable is set to
nulland being passed into a module. That module is attempting to set up an AWS SG rule, but there is no immeidately apparent way to "massage" a null value into an empty list that thecompact/concatfunctions will accept.Additional Context
There does not appear to be anything else that's relevant.
References
None that immediately come to mind.
TL:DR: A
nullvalue is being passed into theconcat()function. This results in a stack trace. I believe that this is something that can be caught/handled in a more elegant way.The null value is being passed in because i can't figure out the expression needed for checking if a variable is null and using that check to conditionally not create a resource.
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