Dot indexing worked in the "regexps and strings" world of 0.6.x, but it
no longer works on the 0.7 series w/ proper List / Map types.
There is plenty of dot-indexed config out in the wild, so we need to do
what we can to point users to the new syntax.
Here is one place we can do it for user variables (`var.somemap`). We'll
also need to address Resource Variables and Module Variables in a
separate PR.
This fixes the panic in #7103 - a proper error message is now returned.
This allows ${data.TYPE.NAME.FIELD} interpolation syntax at the
configuration level, though since there is no special handling of them
in the core package this currently just acts as an alias for
${TYPE.NAME.FIELD}.
This commit adds support for native list variables and outputs, building
up on the previous change to state. Interpolation functions now return
native lists in preference to StringList.
List variables are defined like this:
variable "test" {
# This can also be inferred
type = "list"
default = ["Hello", "World"]
}
output "test_out" {
value = "${var.a_list}"
}
This results in the following state:
```
...
"outputs": {
"test_out": [
"hello",
"world"
]
},
...
```
And the result of terraform output is as follows:
```
$ terraform output
test_out = [
hello
world
]
```
Using the output name, an xargs-friendly representation is output:
```
$ terraform output test_out
hello
world
```
The output command also supports indexing into the list (with
appropriate range checking and no wrapping):
```
$ terraform output test_out 1
world
```
Along with maps, list outputs from one module may be passed as variables
into another, removing the need for the `join(",", var.list_as_string)`
and `split(",", var.list_as_string)` which was previously necessary in
Terraform configuration.
This commit also updates the tests and implementations of built-in
interpolation functions to take and return native lists where
appropriate.
A backwards compatibility note: previously the concat interpolation
function was capable of concatenating either strings or lists. The
strings use case was deprectated a long time ago but still remained.
Because we cannot return `ast.TypeAny` from an interpolation function,
this use case is no longer supported for strings - `concat` is only
capable of concatenating lists. This should not be a huge issue - the
type checker picks up incorrect parameters, and the native HIL string
concatenation - or the `join` function - can be used to replicate the
missing behaviour.
Building on the work of #3846, deprecate `filename` in favor of a
`template` attribute that accepts file contents instead of a path.
Required a bit of work in the interpolation code to prevent Terraform
from assuming that template interpolations were resource variables that
needed to be resolved. Leaving them as "Unknown Variables" prevents
interpolation from happening early and lets the `template_file` resource
do its thing.
Paul Hinze