Multiconf, defining host dependent Sublime Text plugin configuration values

multiconf.py

import socket
import sublime
import re

""" Copyright (C) 2012 Isaac Muse

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Licensed under MIT.

Thanks to: biermeester and matthjes for their ideas and contributions

Multiconf is a module that allows you to read platforma and/or host
specific configuration values to be used by Sublime Text 2 plugins.

Using this module's `get` function, allows the user to replace any settings
value in a '.settings' file with a dictionary containing multiple values.

Mulitconf does this by using a dictionary with a special identifier
"#multiconf#"  and a list of dictionaries identified by a qualifier of the form

    "<qualifier name>:<qualifier value>[;<qualifier name>:<qualifier value>]..."

For example, the following setting

    "user_home": "/home"

would result in `get("user_home")` returning the value "/home" but it could also
be replaced with

    "user_home":  {
                    "#multiconf#": [
                        {"os:windows": "C:\\Users"},
                        {"os:linux;host:his_pc": "/home"},
                        {"os:linux;host:her_pc": "/home/her/special"}
                    ]
    }

Now the same configuration file will provide different values depending on the
machine it's on. On an MS Windows machine the value returned by `get` will be
"C:\Users", and on a Linux machine with the host name 'his_pc' the value will be
"/home".
"""

__version__ = "1.0"

__CURRENT_HOSTNAME = socket.gethostname().lower()
__CURRENT_PLATFORM = sublime.platform()

QUALIFIERS = r"""([A-Za-z\d_]*):([^;]*)(?:;|$)"""


def get(settings_obj, key, default=None, callback=None):
    """
    Return a Sublime Text plugin setting value

    Parameters:
      settings_obj - a sublime.Settings object or a dictionary containing
                     settings
      key          - the name of the setting
      default      - the default value to return if the key value is not found.
      callback     - a callback function that, if provided, will be called with
                     the found and default values as parameters.

    """
    # Parameter validation
    if not isinstance(settings_obj, (dict, sublime.Settings)):
        raise AttributeError("Invalid settings object")
    if not isinstance(key, basestring):
        raise AttributeError("Invalid callback function")
    if callback != None and not hasattr(callback, '__call__'):
        raise AttributeError("Invalid callback function")

    setting = settings_obj.get(key, default)
    final_val = None

    if isinstance(setting, dict) and "#multiconf#" in setting:
        reject_item = False
        for entry in setting["#multiconf#"]:
            reject_item = False if isinstance(entry, dict) and len(entry) else True

            k, v = entry.popitem()

            if reject_item:
                continue

            for qual in re.compile(QUALIFIERS).finditer(k):
                if Qualifications.exists(qual.group(1)):
                    reject_item = not Qualifications.eval_qual(qual.group(1), qual.group(2))
                else:
                    reject_item = True
                if reject_item:
                    break

            if not reject_item:
                final_val = v
                break

        if reject_item:
            final_val = default
    else:
        final_val = setting

    return callback(final_val, default) if callback else final_val


class QualException(Exception):
    pass


class Qualifications(object):
    __qualifiers = {}

    @classmethod
    def add_qual(cls, key, callback):
        if isinstance(key, basestring) and re.match(r"^[a-zA-Z][a-zA-Z\d_]*$", key) == None:
            raise QualException("'%s' is not a valid function name." % key)
        if not hasattr(callback, '__call__'):
            raise QualException("Bad function callback.")
        if key in cls.__qualifiers:
            raise QualException("'%s' qualifier already exists." % key)

        cls.__qualifiers[key] = callback

    @classmethod
    def exists(cls, key):
        return (key in cls.__qualifiers)

    @classmethod
    def eval_qual(cls, key, value):
        try:
            return cls.__qualifiers[key](value)
        except:
            raise QualException("Failed to execute %s qualifier" % key)


def __host_match(h):
    return (h.lower() == __CURRENT_HOSTNAME)


def __os_match(os):
    return (os == __CURRENT_PLATFORM)


Qualifications.add_qual("host", __host_match)
Qualifications.add_qual("os", __os_match)

test.py

import multiconf

test = {
    "option": {
        "#multiconf#": [
            {"os:linux": "some/path/here"},
            {"os:windows": "some/other/path/here"}
        ]
    },

    "option2": {
        "#multiconf#": [
            {"os:windows;host:mypc-linux": "some/path/here"},
            {"os:windows;host:mypc": "some/other/path/here"}
        ]
    },

    "option3": {
        "#multiconf#": [
            {"host:mypc;os:linux": {"some_key": True, "some_other_key": "some/path1/here"}},
            {"host:mypc;os:windows": {"some_key": False, "some_other_key": "some/path2/here"}}
        ]
    },

    "option4": "just/a/path"
}


def test_value(val, default=None):
    return val["some_other_key"] if "some_key" in val and val["some_key"] else default


print multiconf.get(test, "option", "None found!")
print multiconf.get(test, "option2", "None found!")
print multiconf.get(test, "option3", "None found!", test_value)
print multiconf.get(test, "option4", "None found!")

@nfarrar I think an absolute path will do the job