vars.py

# (c) 2012-2014, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

# Make coding more python3-ish
from splitter import parse_kv
from unicode import to_unicode

__metaclass__ = type

import ast
from json import dumps
from collections import MutableMapping

DEFAULT_HASH_BEHAVIOUR = "merge"


def _validate_mutable_mappings(a, b):
    """
    Internal convenience function to ensure arguments are MutableMappings

    This checks that all arguments are MutableMappings or raises an error

    :raises AnsibleError: if one of the arguments is not a MutableMapping
    """

    # If this becomes generally needed, change the signature to operate on
    # a variable number of arguments instead.

    if not (isinstance(a, MutableMapping) and isinstance(b, MutableMapping)):
        myvars = []
        for x in [a, b]:
            try:
                myvars.append(dumps(x))
            except:
                myvars.append(to_unicode(x))
        raise ValueError("failed to combine variables, expected dicts but got a '{0}' and a '{1}': \n{2}\n{3}".format(
            a.__class__.__name__, b.__class__.__name__, myvars[0], myvars[1])
        )

def combine_vars(a, b):
    """
    Return a copy of dictionaries of variables based on configured hash behavior
    """

    if DEFAULT_HASH_BEHAVIOUR == "merge":
        return merge_hash(a, b)
    else:
        # HASH_BEHAVIOUR == 'replace'
        _validate_mutable_mappings(a, b)
        result = a.copy()
        result.update(b)
        return result

def merge_hash(a, b):
    """
    Recursively merges hash b into a so that keys from b take precedence over keys from a
    """

    _validate_mutable_mappings(a, b)

    # if a is empty or equal to b, return b
    if a == {} or a == b:
        return b.copy()

    # if b is empty the below unfolds quickly
    result = a.copy()

    # next, iterate over b keys and values
    for k, v in b.items():
        # if there's already such key in a
        # and that key contains a MutableMapping
        if k in result and isinstance(result[k], MutableMapping) and isinstance(v, MutableMapping):
            # merge those dicts recursively
            result[k] = merge_hash(result[k], v)
        else:
            # otherwise, just copy the value from b to a
            result[k] = v

    return result

def load_extra_vars(loader, options):
    extra_vars = {}
    for extra_vars_opt in options.extra_vars:
        extra_vars_opt = to_unicode(extra_vars_opt, errors='strict')
        if extra_vars_opt.startswith(u"@"):
            # Argument is a YAML file (JSON is a subset of YAML)
            data = loader.load_from_file(extra_vars_opt[1:])
        elif extra_vars_opt and extra_vars_opt[0] in u'[{':
            # Arguments as YAML
            data = loader.load(extra_vars_opt)
        else:
            # Arguments as Key-value
            data = parse_kv(extra_vars_opt)
        extra_vars = combine_vars(extra_vars, data)
    return extra_vars

def load_options_vars(options):
    options_vars = {}
    # For now only return check mode, but we can easily return more
    # options if we need variables for them
    options_vars['ansible_check_mode'] = options.check
    return options_vars

def isidentifier(ident):
    """
    Determines, if string is valid Python identifier using the ast module.
    Orignally posted at: http://stackoverflow.com/a/29586366
    """

    if not isinstance(ident, str):
        return False

    try:
        root = ast.parse(ident)
    except SyntaxError:
        return False

    if not isinstance(root, ast.Module):
        return False

    if len(root.body) != 1:
        return False

    if not isinstance(root.body[0], ast.Expr):
        return False

    if not isinstance(root.body[0].value, ast.Name):
        return False

    if root.body[0].value.id != ident:
        return False

    return True