Synnefo

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class Example(object):

    """Example settings are mandatory to be configured with real values.

    There are no defaults, and not giving a value is a fatal error.

    """

    def __init__(self, example_value, description=None):

        self.example_value = example_value

        self.default_value = None

        self.description = description

class Default(object):

    """Default settings are not mandatory in nature.

    There are default values that are meant to work well,

    and also serve as an example.

    """

    def __init__(self, default_value, example=None, description=None):

        self.default_value = default_value

        if example is None:

            example = default_value

        self.example_value = example

        self.description = description

class Deprecated(object):

    """Deprecated settings must be removed, renamed, or otherwise fixed."""

    def __init__(self, rename_to=None, description=None):

        self.rename_to = rename_to

        self.description = description

def get_all_settings(settings):

    var_list = []

    for name in dir(settings):

        if not name.isupper() or name.startswith('_'):

            continue

        var_list.append((name, getattr(settings, name)))

    return var_list

def preproc_settings(settings):

    other = {}

    defaults = {}

    mandatory = {}

    deprecated = {}

    for name, value in get_all_settings(settings):

        if isinstance(value, Example):

            mandatory[name] = value

        elif isinstance(value, Default):

            defaults[name] = value

            setattr(settings, name, value.default_value)

        elif isinstance(value, Deprecated):

            deprecated[name] = value

        else:

            other[name] = value

    settings._OTHER = other

    settings._DEFAULTS = defaults

    settings._MANDATORY = mandatory

    settings._DEPRECATED = deprecated

def postproc_settings(settings):

    configured = {}

    defaults = settings._DEFAULTS

    failed = []

    import os

    relax_mandatory = bool(os.environ.get('SYNNEFO_RELAX_MANDATORY_SETTINGS'))

    for name, value in get_all_settings(settings):

        if isinstance(value, Example):

            if relax_mandatory:

                setattr(settings, name, value.example_value)

            else:

                m = ("Setting '{name}' is mandatory. "

                     "Please provide a real value. "

                     "Example value: '{example}'")

                m = m.format(name=name, example=value.example_value)

                failed.append(m)

        elif isinstance(value, Default):

            m = "unprocessed default setting in post processing"

            raise AssertionError(m)

            defaults[name] = value

            setattr(settings, name, value.default_value)

        elif isinstance(value, Deprecated):

            m = "Setting '{name}' has been deprecated.".format(name=name)

            if value.rename_to:

                m += " Please rename it to '{rename}'.".format(

                    rename=value.rename_to)

            if value.description:

                m += "details: {desc}".format(desc=value.description)

            failed.append(m)

        elif name in defaults:

            if defaults[name].default_value is not value:

                configured[name] = value

    settings._CONFIGURED = configured

    if failed:

        import sys

        sys.stderr.write('\n')

        sys.stderr.write('\n'.join(failed))

        sys.stderr.write('\n\n')

        raise AssertionError("Failed to read settings.")