Source code for confuse.core

# -*- coding: utf-8 -*-
# This file is part of Confuse.
# Copyright 2016, Adrian Sampson.
#
# 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.

"""Worry-free YAML configuration files.
"""
from __future__ import division, absolute_import, print_function

import errno
import os
import yaml
from collections import OrderedDict

from . import util
from . import templates
from . import yaml_util
from .sources import ConfigSource, EnvSource, YamlSource
from .exceptions import ConfigTypeError, NotFoundError, ConfigError

CONFIG_FILENAME = 'config.yaml'
DEFAULT_FILENAME = 'config_default.yaml'
ROOT_NAME = 'root'

REDACTED_TOMBSTONE = 'REDACTED'


# Views and sources.


[docs]class ConfigView(object): """A configuration "view" is a query into a program's configuration data. A view represents a hypothetical location in the configuration tree; to extract the data from the location, a client typically calls the ``view.get()`` method. The client can access children in the tree (subviews) by subscripting the parent view (i.e., ``view[key]``). """ name = None """The name of the view, depicting the path taken through the configuration in Python-like syntax (e.g., ``foo['bar'][42]``). """
[docs] def resolve(self): """The core (internal) data retrieval method. Generates (value, source) pairs for each source that contains a value for this view. May raise `ConfigTypeError` if a type error occurs while traversing a source. """ raise NotImplementedError
[docs] def first(self): """Return a (value, source) pair for the first object found for this view. This amounts to the first element returned by `resolve`. If no values are available, a `NotFoundError` is raised. """ pairs = self.resolve() try: return util.iter_first(pairs) except ValueError: raise NotFoundError(u"{0} not found".format(self.name))
[docs] def exists(self): """Determine whether the view has a setting in any source. """ try: self.first() except NotFoundError: return False return True
[docs] def add(self, value): """Set the *default* value for this configuration view. The specified value is added as the lowest-priority configuration data source. """ raise NotImplementedError
[docs] def set(self, value): """*Override* the value for this configuration view. The specified value is added as the highest-priority configuration data source. """ raise NotImplementedError
[docs] def root(self): """The RootView object from which this view is descended. """ raise NotImplementedError
def __repr__(self): return '<{}: {}>'.format(self.__class__.__name__, self.name) def __iter__(self): """Iterate over the keys of a dictionary view or the *subviews* of a list view. """ # Try iterating over the keys, if this is a dictionary view. try: for key in self.keys(): yield key except ConfigTypeError: # Otherwise, try iterating over a list view. try: for subview in self.sequence(): yield subview except ConfigTypeError: item, _ = self.first() raise ConfigTypeError( u'{0} must be a dictionary or a list, not {1}'.format( self.name, type(item).__name__ ) ) def __getitem__(self, key): """Get a subview of this view.""" return Subview(self, key) def __setitem__(self, key, value): """Create an overlay source to assign a given key under this view. """ self.set({key: value}) def __contains__(self, key): return self[key].exists()
[docs] def set_args(self, namespace, dots=False): """Overlay parsed command-line arguments, generated by a library like argparse or optparse, onto this view's value. :param namespace: Dictionary or Namespace to overlay this config with. Supports nested Dictionaries and Namespaces. :type namespace: dict or Namespace :param dots: If True, any properties on namespace that contain dots (.) will be broken down into child dictionaries. :Example: {'foo.bar': 'car'} # Will be turned into {'foo': {'bar': 'car'}} :type dots: bool """ self.set(util.build_dict(namespace, sep='.' if dots else ''))
# Magical conversions. These special methods make it possible to use # View objects somewhat transparently in certain circumstances. For # example, rather than using ``view.get(bool)``, it's possible to # just say ``bool(view)`` or use ``view`` in a conditional. def __str__(self): """Get the value for this view as a bytestring. """ if util.PY3: return self.__unicode__() else: return bytes(self.get()) def __unicode__(self): """Get the value for this view as a Unicode string. """ return util.STRING(self.get()) def __nonzero__(self): """Gets the value for this view as a boolean. (Python 2 only.) """ return self.__bool__() def __bool__(self): """Gets the value for this view as a boolean. (Python 3 only.) """ return bool(self.get()) # Dictionary emulation methods.
[docs] def keys(self): """Returns a list containing all the keys available as subviews of the current views. This enumerates all the keys in *all* dictionaries matching the current view, in contrast to ``view.get(dict).keys()``, which gets all the keys for the *first* dict matching the view. If the object for this view in any source is not a dict, then a `ConfigTypeError` is raised. The keys are ordered according to how they appear in each source. """ keys = [] for dic, _ in self.resolve(): try: cur_keys = dic.keys() except AttributeError: raise ConfigTypeError( u'{0} must be a dict, not {1}'.format( self.name, type(dic).__name__ ) ) for key in cur_keys: if key not in keys: keys.append(key) return keys
[docs] def items(self): """Iterates over (key, subview) pairs contained in dictionaries from *all* sources at this view. If the object for this view in any source is not a dict, then a `ConfigTypeError` is raised. """ for key in self.keys(): yield key, self[key]
[docs] def values(self): """Iterates over all the subviews contained in dictionaries from *all* sources at this view. If the object for this view in any source is not a dict, then a `ConfigTypeError` is raised. """ for key in self.keys(): yield self[key]
# List/sequence emulation.
[docs] def sequence(self): """Iterates over the subviews contained in lists from the *first* source at this view. If the object for this view in the first source is not a list or tuple, then a `ConfigTypeError` is raised. """ try: collection, _ = self.first() except NotFoundError: return if not isinstance(collection, (list, tuple)): raise ConfigTypeError( u'{0} must be a list, not {1}'.format( self.name, type(collection).__name__ ) ) # Yield all the indices in the sequence. for index in range(len(collection)): yield self[index]
[docs] def all_contents(self): """Iterates over all subviews from collections at this view from *all* sources. If the object for this view in any source is not iterable, then a `ConfigTypeError` is raised. This method is intended to be used when the view indicates a list; this method will concatenate the contents of the list from all sources. """ for collection, _ in self.resolve(): try: it = iter(collection) except TypeError: raise ConfigTypeError( u'{0} must be an iterable, not {1}'.format( self.name, type(collection).__name__ ) ) for value in it: yield value
# Validation and conversion.
[docs] def flatten(self, redact=False): """Create a hierarchy of OrderedDicts containing the data from this view, recursively reifying all views to get their represented values. If `redact` is set, then sensitive values are replaced with the string "REDACTED". """ od = OrderedDict() for key, view in self.items(): if redact and view.redact: od[key] = REDACTED_TOMBSTONE else: try: od[key] = view.flatten(redact=redact) except ConfigTypeError: od[key] = view.get() return od
[docs] def get(self, template=templates.REQUIRED): """Retrieve the value for this view according to the template. The `template` against which the values are checked can be anything convertible to a `Template` using `as_template`. This means you can pass in a default integer or string value, for example, or a type to just check that something matches the type you expect. May raise a `ConfigValueError` (or its subclass, `ConfigTypeError`) or a `NotFoundError` when the configuration doesn't satisfy the template. """ return templates.as_template(template).value(self, template)
# Shortcuts for common templates.
[docs] def as_filename(self): """Get the value as a path. Equivalent to `get(Filename())`. """ return self.get(templates.Filename())
[docs] def as_path(self): """Get the value as a `pathlib.Path` object. Equivalent to `get(Path())`. """ return self.get(templates.Path())
[docs] def as_choice(self, choices): """Get the value from a list of choices. Equivalent to `get(Choice(choices))`. """ return self.get(templates.Choice(choices))
[docs] def as_number(self): """Get the value as any number type: int or float. Equivalent to `get(Number())`. """ return self.get(templates.Number())
[docs] def as_str_seq(self, split=True): """Get the value as a sequence of strings. Equivalent to `get(StrSeq(split=split))`. """ return self.get(templates.StrSeq(split=split))
[docs] def as_pairs(self, default_value=None): """Get the value as a sequence of pairs of two strings. Equivalent to `get(Pairs(default_value=default_value))`. """ return self.get(templates.Pairs(default_value=default_value))
[docs] def as_str(self): """Get the value as a (Unicode) string. Equivalent to `get(unicode)` on Python 2 and `get(str)` on Python 3. """ return self.get(templates.String())
[docs] def as_str_expanded(self): """Get the value as a (Unicode) string, with env vars expanded by `os.path.expandvars()`. """ return self.get(templates.String(expand_vars=True))
# Redaction. @property def redact(self): """Whether the view contains sensitive information and should be redacted from output. """ return () in self.get_redactions() @redact.setter def redact(self, flag): self.set_redaction((), flag)
[docs] def set_redaction(self, path, flag): """Add or remove a redaction for a key path, which should be an iterable of keys. """ raise NotImplementedError()
[docs] def get_redactions(self): """Get the set of currently-redacted sub-key-paths at this view. """ raise NotImplementedError()
[docs]class RootView(ConfigView): """The base of a view hierarchy. This view keeps track of the sources that may be accessed by subviews. """ def __init__(self, sources): """Create a configuration hierarchy for a list of sources. At least one source must be provided. The first source in the list has the highest priority. """ self.sources = list(sources) self.name = ROOT_NAME self.redactions = set()
[docs] def add(self, obj): self.sources.append(ConfigSource.of(obj))
[docs] def set(self, value): self.sources.insert(0, ConfigSource.of(value))
[docs] def resolve(self): return ((dict(s), s) for s in self.sources)
[docs] def clear(self): """Remove all sources (and redactions) from this configuration. """ del self.sources[:] self.redactions.clear()
[docs] def root(self): return self
[docs] def set_redaction(self, path, flag): if flag: self.redactions.add(path) elif path in self.redactions: self.redactions.remove(path)
[docs] def get_redactions(self): return self.redactions
[docs]class Subview(ConfigView): """A subview accessed via a subscript of a parent view.""" def __init__(self, parent, key): """Make a subview of a parent view for a given subscript key. """ self.parent = parent self.key = key # Choose a human-readable name for this view. if isinstance(self.parent, RootView): self.name = '' else: self.name = self.parent.name if not isinstance(self.key, int): self.name += '.' if isinstance(self.key, int): self.name += u'#{0}'.format(self.key) elif isinstance(self.key, bytes): self.name += self.key.decode('utf-8') elif isinstance(self.key, util.STRING): self.name += self.key else: self.name += repr(self.key)
[docs] def resolve(self): for collection, source in self.parent.resolve(): try: value = collection[self.key] except IndexError: # List index out of bounds. continue except KeyError: # Dict key does not exist. continue except TypeError: # Not subscriptable. raise ConfigTypeError( u"{0} must be a collection, not {1}".format( self.parent.name, type(collection).__name__ ) ) yield value, source
[docs] def set(self, value): self.parent.set({self.key: value})
[docs] def add(self, value): self.parent.add({self.key: value})
[docs] def root(self): return self.parent.root()
[docs] def set_redaction(self, path, flag): self.parent.set_redaction((self.key,) + path, flag)
[docs] def get_redactions(self): return (kp[1:] for kp in self.parent.get_redactions() if kp and kp[0] == self.key)
# Main interface.
[docs]class Configuration(RootView): def __init__(self, appname, modname=None, read=True, loader=yaml_util.Loader): """Create a configuration object by reading the automatically-discovered config files for the application for a given name. If `modname` is specified, it should be the import name of a module whose package will be searched for a default config file. (Otherwise, no defaults are used.) Pass `False` for `read` to disable automatic reading of all discovered configuration files. Use this when creating a configuration object at module load time and then call the `read` method later. Specify the Loader class as `loader`. """ super(Configuration, self).__init__([]) self.appname = appname self.modname = modname self.loader = loader # Resolve default source location. We do this ahead of time to # avoid unexpected problems if the working directory changes. if self.modname: self._package_path = util.find_package_path(self.modname) else: self._package_path = None self._env_var = '{0}DIR'.format(self.appname.upper()) if read: self.read()
[docs] def user_config_path(self): """Points to the location of the user configuration. The file may not exist. """ return os.path.join(self.config_dir(), CONFIG_FILENAME)
[docs] def _add_user_source(self): """Add the configuration options from the YAML file in the user's configuration directory (given by `config_dir`) if it exists. """ filename = self.user_config_path() self.add(YamlSource(filename, loader=self.loader, optional=True))
[docs] def _add_default_source(self): """Add the package's default configuration settings. This looks for a YAML file located inside the package for the module `modname` if it was given. """ if self.modname: if self._package_path: filename = os.path.join(self._package_path, DEFAULT_FILENAME) self.add(YamlSource(filename, loader=self.loader, optional=True, default=True))
[docs] def read(self, user=True, defaults=True): """Find and read the files for this configuration and set them as the sources for this configuration. To disable either discovered user configuration files or the in-package defaults, set `user` or `defaults` to `False`. """ if user: self._add_user_source() if defaults: self._add_default_source()
[docs] def config_dir(self): """Get the path to the user configuration directory. The directory is guaranteed to exist as a postcondition (one may be created if none exist). If the application's ``...DIR`` environment variable is set, it is used as the configuration directory. Otherwise, platform-specific standard configuration locations are searched for a ``config.yaml`` file. If no configuration file is found, a fallback path is used. """ # If environment variable is set, use it. if self._env_var in os.environ: appdir = os.environ[self._env_var] appdir = os.path.abspath(os.path.expanduser(appdir)) if os.path.isfile(appdir): raise ConfigError(u'{0} must be a directory'.format( self._env_var )) else: # Search platform-specific locations. If no config file is # found, fall back to the first directory in the list. configdirs = util.config_dirs() for confdir in configdirs: appdir = os.path.join(confdir, self.appname) if os.path.isfile(os.path.join(appdir, CONFIG_FILENAME)): break else: appdir = os.path.join(configdirs[0], self.appname) # Ensure that the directory exists. try: os.makedirs(appdir) except OSError as e: if e.errno != errno.EEXIST: raise return appdir
[docs] def set_file(self, filename, base_for_paths=False): """Parses the file as YAML and inserts it into the configuration sources with highest priority. :param filename: Filename of the YAML file to load. :param base_for_paths: Indicates whether the directory containing the YAML file will be used as the base directory for resolving relative path values stored in the YAML file. Otherwise, by default, the directory returned by `config_dir()` will be used as the base. """ self.set(YamlSource(filename, base_for_paths=base_for_paths, loader=self.loader))
[docs] def set_env(self, prefix=None, sep='__'): """Create a configuration overlay at the highest priority from environment variables. After prefix matching and removal, environment variable names will be converted to lowercase for use as keys within the configuration. If there are nested keys, list-like dicts (ie, `{0: 'a', 1: 'b'}`) will be converted into corresponding lists (ie, `['a', 'b']`). The values of all environment variables will be parsed as YAML scalars using the `self.loader` Loader class to ensure type conversion is consistent with YAML file sources. Use the `EnvSource` class directly to load environment variables using non-default behavior and to enable full YAML parsing of values. :param prefix: The prefix to identify the environment variables to use. Defaults to uppercased `self.appname` followed by an underscore. :param sep: Separator within variable names to define nested keys. """ if prefix is None: prefix = '{0}_'.format(self.appname.upper()) self.set(EnvSource(prefix, sep=sep, loader=self.loader))
[docs] def dump(self, full=True, redact=False): """Dump the Configuration object to a YAML file. The order of the keys is determined from the default configuration file. All keys not in the default configuration will be appended to the end of the file. :param full: Dump settings that don't differ from the defaults as well :param redact: Remove sensitive information (views with the `redact` flag set) from the output """ if full: out_dict = self.flatten(redact=redact) else: # Exclude defaults when flattening. sources = [s for s in self.sources if not s.default] temp_root = RootView(sources) temp_root.redactions = self.redactions out_dict = temp_root.flatten(redact=redact) yaml_out = yaml.dump(out_dict, Dumper=yaml_util.Dumper, default_flow_style=None, indent=4, width=1000) # Restore comments to the YAML text. default_source = None for source in self.sources: if source.default: default_source = source break if default_source and default_source.filename: with open(default_source.filename, 'rb') as fp: default_data = fp.read() yaml_out = yaml_util.restore_yaml_comments( yaml_out, default_data.decode('utf-8')) return yaml_out
[docs] def reload(self): """Reload all sources from the file system. This only affects sources that come from files (i.e., `YamlSource` objects); other sources, such as dictionaries inserted with `add` or `set`, will remain unchanged. """ for source in self.sources: if isinstance(source, YamlSource): source.load()
[docs]class LazyConfig(Configuration): """A Configuration at reads files on demand when it is first accessed. This is appropriate for using as a global config object at the module level. """ def __init__(self, appname, modname=None): super(LazyConfig, self).__init__(appname, modname, False) self._materialized = False # Have we read the files yet? self._lazy_prefix = [] # Pre-materialization calls to set(). self._lazy_suffix = [] # Calls to add().
[docs] def read(self, user=True, defaults=True): self._materialized = True super(LazyConfig, self).read(user, defaults)
[docs] def resolve(self): if not self._materialized: # Read files and unspool buffers. self.read() self.sources += self._lazy_suffix self.sources[:0] = self._lazy_prefix return super(LazyConfig, self).resolve()
[docs] def add(self, value): super(LazyConfig, self).add(value) if not self._materialized: # Buffer additions to end. self._lazy_suffix += self.sources del self.sources[:]
[docs] def set(self, value): super(LazyConfig, self).set(value) if not self._materialized: # Buffer additions to beginning. self._lazy_prefix[:0] = self.sources del self.sources[:]
[docs] def clear(self): """Remove all sources from this configuration.""" super(LazyConfig, self).clear() self._lazy_suffix = [] self._lazy_prefix = []
# "Validated" configuration views: experimental!