Merge pull request #9829 from hashicorp/fix_9789

add variable gotcha to the variables docs not just the from-json hcl …
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Wilken Rivera 2020-08-26 14:07:36 -04:00 committed by GitHub
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@ -168,6 +168,72 @@ $ packer build -var='image_id_map={"us-east-1":"ami-abc123","us-east-2":"ami-def
The `-var` option can be used any number of times in a single command.
If you plan to assign variables via the command line, we strongly recommend that
you at least set a default type instead of using empty blocks; this helps the
HCL parser understand what is being set.
For example:
```hcl
variable "pizza" {
type = string
}
source "null" "example" {
communicator = "none"
}
build {
sources = [
"source.null.example"
]
provisioner "shell-local" {
inline = ["echo $PIZZA"]
environment_vars = ["PIZZA=${var.pizza}"]
}
}
```
If you call the above template using the command
```sh
packer build -var pizza=pineapple shell_local_variables.pkr.hcl
```
then the Packer build will run successfully. However, if you define the variable
using an empty block, the parser will not know what type the variable is, and it
cannot infer the type from the command line, as shown in this example:
```hcl
variable "pizza" {}
source "null" "example" {
communicator = "none"
}
build {
sources = [
"source.null.example"
]
provisioner "shell-local" {
inline = ["echo $PIZZA"]
environment_vars = ["PIZZA=${var.pizza}"]
}
}
```
The above template will result in the error:
```
Error: Variables not allowed
on <value for var.pizza from arguments> line 1:
(source code not available)
Variables may not be used here.
```
You can work around this either by quoting the variable on the command line, or
by adding the type to the variable block as shown in the previous example.
Setting the expected type is the more resilient option.
```sh
packer build -var 'pizza="pineapple"' shell_local_variables.pkr.hcl
```
### Variable Definitions (`.pkrvars.hcl`) Files
To set lots of variables, it is more convenient to specify their values in a