Packer: Shell Provisioner: only override some environment variables?

[chris-leach]

I have a shell provisioner a bit like the following:

{
  "type": "shell",
  "environment_vars": [
    "LIST={{user `var_1`}}",
    "OF={{user `var_2`}}",
    "ENV={{user `var_3`}}",
    "VARS={{user `var_4`}}",
    "NAME={{user `prod_name`}}",
    "ALLOW_SSH=false"
  ],
  "scripts": ["scripts/install.sh"]
}

I want to keep most of these variables the same for all builders (though they may change between runs), but vary e.g. the NAME and ALLOW_SSH variables between builders. As far as I can tell, if I override environment_vars then I have to duplicate the whole list. This is especially inconvenient when there are more variables and I need to override multiple builders:

"override": {
    "ami-dev": {
      "environment_vars": [
        "REALLY={{user `var_1`}}",
        "QUITE={{user `var_2`}}",
        "LONG={{user `var_3`}}",
        "LIST={{user `var_4`}}",
        "OF={{user `var_5`}}",
        "ENV={{user `var_6`}}",
        "VARS={{user `var_7`}}",
        "NAME={{user `ami_name`}}",
        "ALLOW_SSH=true"
      ]
    },
    "ovf-dev": {
      "environment_vars": [
        "REALLY={{user `var_1`}}",
        "QUITE={{user `var_2`}}",
        "LONG={{user `var_3`}}",
        "LIST={{user `var_4`}}",
        "OF={{user `var_5`}}",
        "ENV={{user `var_6`}}",
        "VARS={{user `var_7`}}",
        "NAME={{user `ovf_name`}}",
        "ALLOW_SSH=true"
      ]
    }
},

I can work around this by overriding execute_command: "{{.Vars}} NAME={{user `ami_name`}} ALLOW_SSH=true {{.Path}}" instead, but I think this confuses the intent. It would be really great if overriding environment_vars only overrode those variables that are specified, so that I could simply write:

"override": {
  "ami-dev": {
    "environment_vars": [
      "NAME={{user `ami_name`}}",
      "ALLOW_SSH=true"
    ]
  },
  "ovf-dev": {
    "environment_vars": [
      "NAME={{user `ovf_name`}}",
      "ALLOW_SSH=true"
    ]
  }
},

Variables that actually need to be unset could be overridden with e.g. "REALLY=".

[SwampDragons]

Hi, thanks for reaching out. We're gonna be working on revamping our config as part of the initiative to move it to HCL2 later this year, and I'm going to link this ticket so that we can keep it in mind as we do that work.

[SwampDragons]

See #1768