Flask源码剖析(12): 配置

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# -*- coding: utf-8 -*-

import os
import types
import errno

from werkzeug.utils import import_string
from ._compat import string_types, iteritems
from . import json


class ConfigAttribute(object):

    def __init__(self, name, get_converter=None):
        self.__name__ = name
        self.get_converter = get_converter

    def __get__(self, obj, type=None):
        if obj is None:
            return self
        rv = obj.config[self.__name__]
        if self.get_converter is not None:
            rv = self.get_converter(rv)
        return rv

    def __set__(self, obj, value):
        obj.config[self.__name__] = value


class Config(dict):

    def __init__(self, root_path, defaults=None):
        dict.__init__(self, defaults or {})
        self.root_path = root_path

    def from_envvar(self, variable_name, silent=False):
        rv = os.environ.get(variable_name)
        if not rv:
            if silent:
                return False
            raise RuntimeError('The environment variable %r is not set '
                               'and as such configuration could not be '
                               'loaded.  Set this variable and make it '
                               'point to a configuration file' %
                               variable_name)
        return self.from_pyfile(rv, silent=silent)

    def from_pyfile(self, filename, silent=False):
        filename = os.path.join(self.root_path, filename)
        d = types.ModuleType('config')
        d.__file__ = filename
        try:
            with open(filename) as config_file:
                exec(compile(config_file.read(), filename, 'exec'), d.__dict__)
        except IOError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
                return False
            e.strerror = 'Unable to load configuration file (%s)' % e.strerror
            raise
        self.from_object(d)
        return True

    def from_object(self, obj):
        if isinstance(obj, string_types):
            obj = import_string(obj)
        for key in dir(obj):
            if key.isupper():
                self[key] = getattr(obj, key)

    def from_json(self, filename, silent=False):
        filename = os.path.join(self.root_path, filename)

        try:
            with open(filename) as json_file:
                obj = json.loads(json_file.read())
        except IOError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
                return False
            e.strerror = 'Unable to load configuration file (%s)' % e.strerror
            raise
        return self.from_mapping(obj)

    def from_mapping(self, *mapping, **kwargs):
        mappings = []
        if len(mapping) == 1:
            if hasattr(mapping[0], 'items'):
                mappings.append(mapping[0].items())
            else:
                mappings.append(mapping[0])
        elif len(mapping) > 1:
            raise TypeError(
                'expected at most 1 positional argument, got %d' % len(mapping)
            )
        mappings.append(kwargs.items())
        for mapping in mappings:
            for (key, value) in mapping:
                if key.isupper():
                    self[key] = value
        return True

    def get_namespace(self, namespace, lowercase=True, trim_namespace=True):
        rv = {}
        for k, v in iteritems(self):
            if not k.startswith(namespace):
                continue
            if trim_namespace:
                key = k[len(namespace):]
            else:
                key = k
            if lowercase:
                key = key.lower()
            rv[key] = v
        return rv

    def __repr__(self):
        return '<%s %s>' % (self.__class__.__name__, dict.__repr__(self))