implementation

require.py

"""
require replacement in decorator form

Will raise a NameError exception if a Required fabric enviroment variable is
not set, before calling the decorated task.

Use:
    from fabric.api import env
    from fabric.contrib.require import Require
    
    ...
    
    env['important_variable'] = important_value
    @Require('important_variable')
    def fabric_task():
        ...
"""

from fabric.api import env

class Require(object):
    def __init__(self, *args):
        self.required = set(args)
    
    def __call__(self, function):
        def wrapper(*args, **kwargs):
            available = set(env.keys())
            missing = self.required.difference(available)

            if (missing):
                missing_text = ", ".join(missing)
                raise NameError(
                    "Missing Env Variables: \"%s\" before calling: %s" %
                    (missing_text, function))

            return function(*args, **kwargs)

        wrapper.__name__ = "Require(%s)" % (function.__name__)
        return wrapper