feat: Edit object type

[ryanmills]

I have the following HCL file:

locals {
  workload_1 = {
    vpc0 = {
      cidr_block     = "192.168.1.0/24"
      extended_cidrs = {}
      name_prefix    = "workload"
    }
  }
}

And receive the following outputs:

$ cat test.hcl | hcledit block get locals
locals {
  workload_1 = {
    vpc0 = {
      cidr_block     = "192.168.1.0/24"
      extended_cidrs = {}
      name_prefix    = "workload"
    }
  }
}
$ cat test.hcl | hcledit block get locals.workload_1
$ cat test.hcl | hcledit block get locals.workload_1.vpc0
$ 

No results are returned for locals.workload_1. Not sure why. Thanks!

[minamijoyo]

The locals.workload_1 is an attribute, not a block. We can get it with hcledit attribute get locals.workload_1

$ cat test.hcl | hcledit attribute get locals.workload_1
{
    vpc0 = {
      cidr_block     = "192.168.1.0/24"
      extended_cidrs = {}
      name_prefix    = "workload"
    }
  }

However, The type of workload_1 is an object and the vpc0 is a key of the object, so it would be great if we can get it with hcledit attribute get 'locals.workload_1["vpc0"]', but it's not supported yet.

[ryanmills]

Thanks. For completeness, my use case is:

locals {
  prod_1 = {
    vpc0 = {
      cidr_block     = "1.2.3.4/19"
      extended_cidrs = {}
      name_prefix    = "workload"
      tgw_subnets = {
        a0 = {
          cidr_block        = "1.2.3.4/28"
          name_prefix       = "tgw"
        }
        b0 = {
          cidr_block        = "1.2.3.4/28"
          name_prefix       = "tgw"
        }
        c0 = {
          cidr_block        = "1.2.3.4/28"
          name_prefix       = "tgw"
        }
      }
      ram_subnets = {
        a0 = {
          cidr_block        = "1.2.3.4/28"
          name_prefix       = "ram"
        }
      }
      private_subnets = {
        endpoints_a0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "endpoints"
        }
        endpoints_b0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "endpoints"
        }
        endpoints_c0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "endpoints"
        }
      }
      shared_subnets = {
        data_a0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "shared"
          app_name          = "shared"
        }
        data_b0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "shared"
          app_name          = "shared"
        }
        data_c0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "shared"
          app_name          = "shared"
        }
        compute_a0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "shared"
          app_name          = "shared"
        }
        compute_b0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "shared"
          app_name          = "shared"
        }
        compute_c0 = {
          cidr_block        = "1.2.3.4/26"
          name_prefix       = "shared"
          app_name          = "shared"
        }
      }
    }
  }
}

Trying to extract (and set) the value of locals.prod_1.vpc0.ram_subnets.a0.cidr_block

[minamijoyo]

The hcledit depends on the hclwrite parser in the hcl library which is used by the terraform fmt command and is specialized for the token-based edit to preserve comments. However, at time of this writing, it has very limited capabilities and doesn't have enough AST representations for such a complex object type. So I think it's not possible to support it without extending the hclwrite.

If your concern is only query (not edit), the best way to do this for now is convert it to json with hcl2json and query the json string with jq.

https://github.com/tmccombs/hcl2json

$ cat test.hcl | hcl2json | jq '.locals[0].workload_1.vpc0'
{
  "cidr_block": "192.168.1.0/24",
  "extended_cidrs": {},
  "name_prefix": "workload"
}

[buggtb]

So if I read this correctly, we couldn't add, for example, a tags block into an AWS resource:

  tags = {
    hello = "world"
  }

although actually:

➜  ~ cat ./elastic.tf | ./hcledit attribute get resource.aws_elasticsearch_domain.sample.tags
{
    hello = "world"
    someothertag = "yes"
  }

seems to return the string. And I can set it with

➜  ~ cat ./elastic.tf | ./hcledit attribute set resource.aws_elasticsearch_domain.sample.tags '{ hello="world", somenewtag = "no"}'

so as long as you don't mind replacing the whole block you can do so?

[minamijoyo]

Thank you for pointing out it.

The hcledit uses a token based parser and actually doesn't know what type is correct in application schema, so you can set an object literal as a string.

[wondersd]

One way to work around this for now is to recursively feed attribute blocks back into hcledit as intermediate locals blocks

main.tf

locals {
  map = {
     key = "foo"
  }
}

Normally locals.map is returned as

$ hcledit -f main.tf attribute get locals.map
{
     key = "foo"
  }

Can get the above output to look like a locals block of a new intermediate tf file and to then select the next nested key

$ hcledit -f <(echo "locals $(hcledit -f main.tf attribute get locals.map)") attribute get locals.key
"foo"

This can be implemented recursively to get (and even set) deeply nested attributes of locals, resources, modules, etc