jinja-cli.py

# Script to run Jinja2 reading from template and parameter files
# - Note: Undefined Jinja variables will cause errors
# - Note: 'trim_blocks' and 'lstrip_block are forced to True


def render_template(template_filename, parameters_filename, whitespace, unset_variables, verbose=0):
 import os
 import json
 import yaml
 import sys
 from jinja2 import Template, StrictUndefined

 if os.path.exists(parameters_filename):
 filepath = parameters_filename
 else:
 workdir = os.getcwd()
 filepath = os.path.join(workdir, parameters_filename)

 try:
 file = open(filepath)
 except OSError as os_error:
 print(f"{os_error}", file=sys.stderr)
 sys.exit(1)

 params = None
 try:
 if verbose > 0:
 print(f"trying to JSON load, {file.name}")
 params = json.load(file)
 except json.decoder.JSONDecodeError as json_decode_error:
 file.seek(0) # return to beginning of file
 if verbose > 0:
 print(f"trying to YAML load, {file.name}")
 try:
 params = yaml.safe_load(file)
 except yaml.YAMLError as yaml_error:
 print(f"Parameters file not valid JSON or YAML, {yaml_error}", file=sys.stderr)
 finally:
 file.close()

 # Read the template file
 if os.path.exists(template_filename):
 filepath = template_filename
 else:
 workdir = os.getcwd()
 filepath = os.path.join(workdir, template_filename)

 template = None
 try:
 file = open(filepath)
 template = file.read()
 except OSError as os_error:
 print(f"{os_error}", file=sys.stderr)
 sys.exit(1)

 if whitespace and unset_variables:
 j2_template = Template(template)
 elif whitespace:
 j2_template = Template(template, undefined=StrictUndefined)
 elif unset_variables:
 j2_template = Template(template, trim_blocks=True, lstrip_blocks=True)
 else:
 j2_template = Template(template, undefined=StrictUndefined, trim_blocks=True, lstrip_blocks=True)

 print(j2_template.render(params))


if __name__ == '__main__':
 import argparse

 arguments = None
 parser = argparse.ArgumentParser(description='Simple Jinja2 CLI tool')
 parser.add_argument('-t', '--template', type=str, default=None, help='template file', required=True)
 parser.add_argument('-p', '--parameters', type=str, default=None, help='parameters file', required=True)
 parser.add_argument('-w', '--whitespace', help='enable white-space controls', default=False, action='store_true')
 parser.add_argument('-u', '--unset', help='allow unset variables', default=False, action='store_true')
 parser.add_argument('-v', '--verbose', action='count', default=0)
 args = parser.parse_args()

 render_template(
 template_filename=args.template,
 parameters_filename=args.parameters,
 whitespace=args.whitespace,
 unset_variables=args.unset,
 verbose=args.verbose
 )

 exit(0)