✨ Add low-setup usage

This adds the ability to use moban in an ad-hoc manner
without a config file, like `moban foo.jj2`. This also
adds environment variables as a fallback data source if
the default/specified data files do not exist.

Closes moremoban#133

moban/constants.py

@@ -20,6 +20,7 @@
 LABEL_CONFIG = "configuration"
 LABEL_CONFIG_DIR = "configuration_dir"
 LABEL_PLUGIN_DIRS = "plugin_dir"
+LABEL_SIMPLE_TEMPLATE = "simple_template"
 LABEL_TEMPLATE = "template"
 LABEL_TMPL_DIRS = "template_dir"
 LABEL_OUTPUT = "output"

moban/main.py

@@ -60,6 +60,10 @@ def create_parser():
     parser = argparse.ArgumentParser(
         prog=constants.PROGRAM_NAME, description=constants.PROGRAM_DESCRIPTION
     )
+    parser.add_argument(
+        constants.LABEL_SIMPLE_TEMPLATE, metavar=constants.LABEL_TEMPLATE,
+        type=str, nargs='?', help='the template file (low-setup mode)'
+    )
     parser.add_argument(
         "-cd",
         "--%s" % constants.LABEL_CONFIG_DIR,
@@ -153,6 +157,8 @@ def handle_command_line(options):
     act upon command options
     """
     options = merge(options, constants.DEFAULT_OPTIONS)
+    if options[constants.LABEL_SIMPLE_TEMPLATE]:
+        options[constants.LABEL_TEMPLATE] = options[constants.LABEL_SIMPLE_TEMPLATE]
     if options[constants.LABEL_TEMPLATE] is None:
         raise exceptions.NoTemplate(constants.ERROR_NO_TEMPLATE)
     engine = plugins.ENGINES.get_engine(

moban/plugins.py

@@ -46,7 +46,15 @@ def number_of_templated_files(self):
         return self.templated_count
 
     def render_to_file(self, template_file, data_file, output_file):
-        data = self.context.get_data(data_file)
+        try:
+            data = self.context.get_data(data_file)
+        except OSError as exception:
+            # If data file doesn't exist:
+            # 1. Alert the user of their (potential) mistake
+            # 2. Attempt to use environment vars as data
+            reporter.report_error_message(exception)
+            reporter.report_using_env_vars()
+            data = os.environ
         template = self.engine.get_template(template_file)
         template_abs_path = utils.get_template_path(
             self.template_dirs, template_file

moban/reporter.py

@@ -12,6 +12,7 @@
 MESSAGE_COPIED_ALL = "Copied {0} files."
 MESSAGE_PULLING_REPO = "Updating {0}..."
 MESSAGE_CLONING_REPO = "Cloning {0}..."
+MESSAGE_USING_ENV_VARS = "Attempting to use environment vars as data..."
 
 
 def report_templating(source_file, destination_file):
@@ -89,6 +90,10 @@ def report_git_clone(repo):
     print(MESSAGE_CLONING_REPO.format(colored_repo))
 
 
+def report_using_env_vars():
+    print(crayons.yellow(MESSAGE_USING_ENV_VARS, bold=True))
+
+
 def _format_single(message, count):
     if count == 1:
         return message.replace("files", "file")