Bad output value silently ignored

[brainsik]

Naïvely one might expect to be able to use a list as an output (instead of the required string). Doing this produces no error:

output "subnets" {
    value = "${aws_subnet.example.*}"
}

Nor this:

output "subnets" {
    value = "${join(",", aws_subnet.example.*)}"
}

Nor this:

output "subnets" {
    value = "${aws_vpc.example.this-no-exist}"
}

Basically, you end up stumbling around confused why your output isn't showing up. It would be great to get some sort of error message instead of silently dropping the output.

Appears related to #4369.

[eedwardsdisco]

I also got bit by this one.

Out of curiosity, why does your second example fail?

I've successfully used the following, the variable is a list:

output "name_servers" {
    value = "${join(",", aws_route53_zone.domain.name_servers)}"
}

[brainsik]

The second one fails because it's not specifying a field to return. Should be something like aws_subnet.example.*.id to return a list of IDs (that are then converted into a comma separated string).

[eedwardsdisco]

Ah, that's clear now, thanks!

[jen20]

Thanks for reporting this - I agree this should give an error rather than silently dropping the output.

[wr0ngway]

This also happens for bad interpolation function calls, e.g. passing the wrong type or number of args to a interpolation function, e.g. compact("x", "y")

[mitchellh]

This is actually tracked as "core+bug" issue #4975. I'm centralizing there!

[rhettg]

@mitchellh you centralized #4975 to this issue, forming a frustrating cycle.

Is there a more canonical issue that could be linked?

[mitchellh]

Oh Hah. I made a mistake, #9080 is the open one.

[ghost]

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