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Process YAML and write Packer JSON to STDOUT
#!/usr/bin/python
#
# Usage: packer-config my-template.yaml | packer build -
#
# Constructs a Packer JSON configuration file from the specified YAML
# template file and writes it to STDOUT.
#
# The YAML template format adds some flexibility and readability by
# adding comments and an !include directive, allowing for the
# following template syntax:
#
# variables:
# - ssh_user: ubuntu
# - ssh_pass: ubuntu
# - hostname: host
# builders:
# - !include build/ubuntu-12.04.kvm.yaml
# - !include build/ubuntu-12.04.ami.yaml
# provisioners:
# - !include provision/ubuntu-12.04-base.yaml
# - !include provision/ops-deploy.yaml
# - !include provision/java7.yaml
# - type: shell
# environment_vars: [ 'HOST_NAME={{user `hostname`}}' ]
# script: host/setup.sh
#
# In addition to the !include directive, the resulting YAML is
# post-processed to flatten lists-of-lists in the top level sections,
# allowing includes to contain multiple entries (i.e. running two shell
# scripts in a common provisioner.)
#
# Author: jeremy@jongsma.org
# License: MPLv2
import sys
import os
import yaml
import json
class IncludeLoader(yaml.Loader):
"""
Custom YAML loader that adds an !include constructor for including
other YAML files relative to the current file being parsed.
Example:
section: !include other/file.yaml
"""
def __init__(self, stream):
self._root = os.path.abspath(os.path.split(stream.name)[0])
super(IncludeLoader, self).__init__(stream)
def include(self, node):
path = self.construct_scalar(node)
filename = path if path[0] == '/' else os.path.join(self._root, path)
with open(filename, 'r') as f:
return yaml.load(f, IncludeLoader)
IncludeLoader.add_constructor('!include', IncludeLoader.include)
def parse_yaml(template):
"""
Constructs a Packer JSON configuration file from the specified YAML
template and returns it as a string.
The YAML template format adds some flexibility and readability by
adding comments and an !include directive, allowing for the
following template syntax:
builders:
- !include build/ubuntu-12.04.kvm.yaml
- !include build/ubuntu-12.04.ami.yaml
provisioners:
- !include provision/ubuntu-12.04-base.yaml
- !include provision/ops-deploy.yaml
- !include provision/java7.yaml
- type: shell
script: app/setup.sh
In addition to the !include directive, the resulting YAML is
post-processed to flatten lists-of-lists in the top level sections,
allowing includes to contain lists of multiple entries (i.e. running
two shell scripts in a common provisioner.)
"""
with open(template, 'r') as infile:
parsed = yaml.load(infile, IncludeLoader)
# Flatten sections to allow including lists of steps in each include
for section in ('builders', 'provisioners', 'post-processors'):
if section in parsed:
parsed[section] = [f for l in [e if isinstance(e, list) else [e]
for e in parsed[section]] for f in l]
return json.dumps(parsed)
if __name__ == "__main__":
if len(sys.argv) < 2:
sys.stderr.write("ERROR: No template specified")
sys.exit(1)
if not os.path.exists(sys.argv[1]):
std.stderr.write("ERROR: Template not found: %s" % sys.argv[1])
sys.exit(2)
sys.stdout.write(parse_yaml(sys.argv[1]))
tamsky commented Mar 14, 2016

Thanks for creating this!

What @tamsky said, plus...
Line 107 should be sys.stderr.write not std.stderr.write.

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