This follows #8232 which added the code to generate the code required to parse
HCL files for each packer component.
All old config files of packer will keep on working the same. Packer takes one
argument. When a directory is passed, all files in the folder with a name
ending with “.pkr.hcl” or “.pkr.json” will be parsed using the HCL2 format.
When a file ending with “.pkr.hcl” or “.pkr.json” is passed it will be parsed
using the HCL2 format. For every other case; the old packer style will be used.
## 1. the hcl2template pkg can create a packer.Build from a set of HCL (v2) files
I had to make the packer.coreBuild (which is our one and only packer.Build ) a public struct with public fields
## 2. Components interfaces get a new ConfigSpec Method to read a file from an HCL file.
This is a breaking change for packer plugins.
a packer component can be a: builder/provisioner/post-processor
each component interface now gets a `ConfigSpec() hcldec.ObjectSpec`
which allows packer to tell what is the layout of the hcl2 config meant
to configure that specific component.
This ObjectSpec is sent through the wire (RPC) and a cty.Value is now
sent through the already existing configuration entrypoints:
Provisioner.Prepare(raws ...interface{}) error
Builder.Prepare(raws ...interface{}) ([]string, error)
PostProcessor.Configure(raws ...interface{}) error
close#1768
Example hcl files:
```hcl
// file amazon-ebs-kms-key/run.pkr.hcl
build {
sources = [
"source.amazon-ebs.first",
]
provisioner "shell" {
inline = [
"sleep 5"
]
}
post-processor "shell-local" {
inline = [
"sleep 5"
]
}
}
// amazon-ebs-kms-key/source.pkr.hcl
source "amazon-ebs" "first" {
ami_name = "hcl2-test"
region = "us-east-1"
instance_type = "t2.micro"
kms_key_id = "c729958f-c6ba-44cd-ab39-35ab68ce0a6c"
encrypt_boot = true
source_ami_filter {
filters {
virtualization-type = "hvm"
name = "amzn-ami-hvm-????.??.?.????????-x86_64-gp2"
root-device-type = "ebs"
}
most_recent = true
owners = ["amazon"]
}
launch_block_device_mappings {
device_name = "/dev/xvda"
volume_size = 20
volume_type = "gp2"
delete_on_termination = "true"
}
launch_block_device_mappings {
device_name = "/dev/xvdf"
volume_size = 500
volume_type = "gp2"
delete_on_termination = true
encrypted = true
}
ami_regions = ["eu-central-1"]
run_tags {
Name = "packer-solr-something"
stack-name = "DevOps Tools"
}
communicator = "ssh"
ssh_pty = true
ssh_username = "ec2-user"
associate_public_ip_address = true
}
```
It is simply the best/simplest solution and trying to prevent users from passing and integer here would be like opening a can of worms. Because:
* we cannot make mapstructure validate our duration string ( with an UnmarshalJSON func etc.)
* we cannot make mapstructure spit a string instead of a duration and packer will decode-encode-decode config.
* the hcl2 generated code asks for a string, so this will be enforced by default.
