loader.py

"""A simple configuration system.

Inheritance diagram:

.. inheritance-diagram:: IPython.config.loader
   :parts: 3

Authors
-------
* Brian Granger
* Fernando Perez
* Min RK
"""

#-----------------------------------------------------------------------------
#  Copyright (C) 2008-2011  The IPython Development Team
#
#  Distributed under the terms of the BSD License.  The full license is in
#  the file COPYING, distributed as part of this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

import argparse
import copy
import os
import re
import sys
import json

from IPython.utils.path import filefind, get_ipython_dir
from IPython.utils import py3compat, warn
from IPython.utils.encoding import DEFAULT_ENCODING
from IPython.utils.py3compat import unicode_type, iteritems
from IPython.utils.traitlets import HasTraits, List, Any, TraitError

#-----------------------------------------------------------------------------
# Exceptions
#-----------------------------------------------------------------------------


class ConfigError(Exception):
    pass

class ConfigLoaderError(ConfigError):
    pass

class ConfigFileNotFound(ConfigError):
    pass

class ArgumentError(ConfigLoaderError):
    pass

#-----------------------------------------------------------------------------
# Argparse fix
#-----------------------------------------------------------------------------

# Unfortunately argparse by default prints help messages to stderr instead of
# stdout.  This makes it annoying to capture long help screens at the command
# line, since one must know how to pipe stderr, which many users don't know how
# to do.  So we override the print_help method with one that defaults to
# stdout and use our class instead.

class ArgumentParser(argparse.ArgumentParser):
    """Simple argparse subclass that prints help to stdout by default."""

    def print_help(self, file=None):
        if file is None:
            file = sys.stdout
        return super(ArgumentParser, self).print_help(file)

    print_help.__doc__ = argparse.ArgumentParser.print_help.__doc__

#-----------------------------------------------------------------------------
# Config class for holding config information
#-----------------------------------------------------------------------------

class LazyConfigValue(HasTraits):
    """Proxy object for exposing methods on configurable containers
    
    Exposes:
    
    - append, extend, insert on lists
    - update on dicts
    - update, add on sets
    """
    
    _value = None
    
    # list methods
    _extend = List()
    _prepend = List()
    
    def append(self, obj):
        self._extend.append(obj)
    
    def extend(self, other):
        self._extend.extend(other)
    
    def prepend(self, other):
        """like list.extend, but for the front"""
        self._prepend[:0] = other
    
    _inserts = List()
    def insert(self, index, other):
        if not isinstance(index, int):
            raise TypeError("An integer is required")
        self._inserts.append((index, other))
    
    # dict methods
    # update is used for both dict and set
    _update = Any()
    def update(self, other):
        if self._update is None:
            if isinstance(other, dict):
                self._update = {}
            else:
                self._update = set()
        self._update.update(other)
    
    # set methods
    def add(self, obj):
        self.update({obj})
    
    def get_value(self, initial):
        """construct the value from the initial one
        
        after applying any insert / extend / update changes
        """
        if self._value is not None:
            return self._value
        value = copy.deepcopy(initial)
        if isinstance(value, list):
            for idx, obj in self._inserts:
                value.insert(idx, obj)
            value[:0] = self._prepend
            value.extend(self._extend)
        
        elif isinstance(value, dict):
            if self._update:
                value.update(self._update)
        elif isinstance(value, set):
            if self._update:
                value.update(self._update)
        self._value = value
        return value
    
    def to_dict(self):
        """return JSONable dict form of my data
        
        Currently update as dict or set, extend, prepend as lists, and inserts as list of tuples.
        """
        d = {}
        if self._update:
            d['update'] = self._update
        if self._extend:
            d['extend'] = self._extend
        if self._prepend:
            d['prepend'] = self._prepend
        elif self._inserts:
            d['inserts'] = self._inserts
        return d


def _is_section_key(key):
    """Is a Config key a section name (does it start with a capital)?"""
    if key and key[0].upper()==key[0] and not key.startswith('_'):
        return True
    else:
        return False


class Config(dict):
    """An attribute based dict that can do smart merges."""

    def __init__(self, *args, **kwds):
        dict.__init__(self, *args, **kwds)
        self._ensure_subconfig()
    
    def _ensure_subconfig(self):
        """ensure that sub-dicts that should be Config objects are
        
        casts dicts that are under section keys to Config objects,
        which is necessary for constructing Config objects from dict literals.
        """
        for key in self:
            obj = self[key]
            if _is_section_key(key) \
                    and isinstance(obj, dict) \
                    and not isinstance(obj, Config):
                setattr(self, key, Config(obj))
    
    def _merge(self, other):
        """deprecated alias, use Config.merge()"""
        self.merge(other)
    
    def merge(self, other):
        """merge another config object into this one"""
        to_update = {}
        for k, v in iteritems(other):
            if k not in self:
                to_update[k] = copy.deepcopy(v)
            else: # I have this key
                if isinstance(v, Config) and isinstance(self[k], Config):
                    # Recursively merge common sub Configs
                    self[k].merge(v)
                else:
                    # Plain updates for non-Configs
                    to_update[k] = copy.deepcopy(v)

        self.update(to_update)

    def __contains__(self, key):
        # allow nested contains of the form `"Section.key" in config`
        if '.' in key:
            first, remainder = key.split('.', 1)
            if first not in self:
                return False
            return remainder in self[first]
        
        return super(Config, self).__contains__(key)
    
    # .has_key is deprecated for dictionaries.
    has_key = __contains__
    
    def _has_section(self, key):
        return _is_section_key(key) and key in self
    
    def copy(self):
        return type(self)(dict.copy(self))

    def __copy__(self):
        return self.copy()

    def __deepcopy__(self, memo):
        import copy
        return type(self)(copy.deepcopy(list(self.items())))
    
    def __getitem__(self, key):
        try:
            return dict.__getitem__(self, key)
        except KeyError:
            if _is_section_key(key):
                c = Config()
                dict.__setitem__(self, key, c)
                return c
            else:
                # undefined, create lazy value, used for container methods
                v = LazyConfigValue()
                dict.__setitem__(self, key, v)
                return v

    def __setitem__(self, key, value):
        if _is_section_key(key):
            if not isinstance(value, Config):
                raise ValueError('values whose keys begin with an uppercase '
                                 'char must be Config instances: %r, %r' % (key, value))
        dict.__setitem__(self, key, value)

    def __getattr__(self, key):
        if key.startswith('__'):
            return dict.__getattr__(self, key)
        try:
            return self.__getitem__(key)
        except KeyError as e:
            raise AttributeError(e)

    def __setattr__(self, key, value):
        if key.startswith('__'):
            return dict.__setattr__(self, key, value)
        try:
            self.__setitem__(key, value)
        except KeyError as e:
            raise AttributeError(e)

    def __delattr__(self, key):
        if key.startswith('__'):
            return dict.__delattr__(self, key)
        try:
            dict.__delitem__(self, key)
        except KeyError as e:
            raise AttributeError(e)


#-----------------------------------------------------------------------------
# Config loading classes
#-----------------------------------------------------------------------------


class ConfigLoader(object):
    """A object for loading configurations from just about anywhere.

    The resulting configuration is packaged as a :class:`Struct`.

    Notes
    -----
    A :class:`ConfigLoader` does one thing: load a config from a source
    (file, command line arguments) and returns the data as a :class:`Struct`.
    There are lots of things that :class:`ConfigLoader` does not do.  It does
    not implement complex logic for finding config files.  It does not handle
    default values or merge multiple configs.  These things need to be
    handled elsewhere.
    """

    def __init__(self):
        """A base class for config loaders.

        Examples
        --------

        >>> cl = ConfigLoader()
        >>> config = cl.load_config()
        >>> config
        {}
        """
        self.clear()

    def clear(self):
        self.config = Config()

    def load_config(self):
        """Load a config from somewhere, return a :class:`Config` instance.

        Usually, this will cause self.config to be set and then returned.
        However, in most cases, :meth:`ConfigLoader.clear` should be called
        to erase any previous state.
        """
        self.clear()
        return self.config


class FileConfigLoader(ConfigLoader):
    """A base class for file based configurations.

    As we add more file based config loaders, the common logic should go
    here.
    """

    def __init__(self, filename, path=None):
        """Build a config loader for a filename and path.

        Parameters
        ----------
        filename : str
            The file name of the config file.
        path : str, list, tuple
            The path to search for the config file on, or a sequence of
            paths to try in order.
        """
        super(FileConfigLoader, self).__init__()
        self.filename = filename
        self.path = path
        self.full_filename = ''

    def _find_file(self):
        """Try to find the file by searching the paths."""
        self.full_filename = filefind(self.filename, self.path)

class JSONFileConfigLoader(FileConfigLoader):
    """A Json file loader for config"""

    def load_config(self):
        """Load the config from a file and return it as a Struct."""
        self.clear()
        try:
            self._find_file()
        except IOError as e:
            raise ConfigFileNotFound(str(e))
        dct = self._read_file_as_dict()
        self.config = self._convert_to_config(dct)
        return self.config

    def _read_file_as_dict(self):
        with open(self.full_filename) as f :
            return json.load(f)

    def _convert_to_config(self, dictionary):
        if 'version' not in dictionary:
            version = dictionary.pop('version')
        else :
            version = 1
            warn.warn("Unrecognized JSON config file version, assuming version : {}".format(version))

        if version == 1:
            return Config(dictionary)
        else :
            raise ValueError('Unknown version of JSON config file : version number {n}'.format(version))


class PyFileConfigLoader(FileConfigLoader):
    """A config loader for pure python files.

    This calls execfile on a plain python file and looks for attributes
    that are all caps.  These attribute are added to the config Struct.
    """

    def load_config(self):
        """Load the config from a file and return it as a Struct."""
        self.clear()
        try:
            self._find_file()
        except IOError as e:
            raise ConfigFileNotFound(str(e))
        self._read_file_as_dict()
        return self.config


    def _read_file_as_dict(self):
        """Load the config file into self.config, with recursive loading."""
        # This closure is made available in the namespace that is used
        # to exec the config file.  It allows users to call
        # load_subconfig('myconfig.py') to load config files recursively.
        # It needs to be a closure because it has references to self.path
        # and self.config.  The sub-config is loaded with the same path
        # as the parent, but it uses an empty config which is then merged
        # with the parents.

        # If a profile is specified, the config file will be loaded
        # from that profile

        def load_subconfig(fname, profile=None):
            # import here to prevent circular imports
            from IPython.core.profiledir import ProfileDir, ProfileDirError
            if profile is not None:
                try:
                    profile_dir = ProfileDir.find_profile_dir_by_name(
                            get_ipython_dir(),
                            profile,
                    )
                except ProfileDirError:
                    return
                path = profile_dir.location
            else:
                path = self.path
            loader = PyFileConfigLoader(fname, path)
            try:
                sub_config = loader.load_config()
            except ConfigFileNotFound:
                # Pass silently if the sub config is not there. This happens
                # when a user s using a profile, but not the default config.
                pass
            else:
                self.config.merge(sub_config)

        # Again, this needs to be a closure and should be used in config
        # files to get the config being loaded.
        def get_config():
            return self.config

        namespace = dict(
            load_subconfig=load_subconfig,
            get_config=get_config,
            __file__=self.full_filename,
        )
        fs_encoding = sys.getfilesystemencoding() or 'ascii'
        conf_filename = self.full_filename.encode(fs_encoding)
        py3compat.execfile(conf_filename, namespace)


class CommandLineConfigLoader(ConfigLoader):
    """A config loader for command line arguments.

    As we add more command line based loaders, the common logic should go
    here.
    """

    def _exec_config_str(self, lhs, rhs):
        """execute self.config.<lhs> = <rhs>
        
        * expands ~ with expanduser
        * tries to assign with raw eval, otherwise assigns with just the string,
          allowing `--C.a=foobar` and `--C.a="foobar"` to be equivalent.  *Not*
          equivalent are `--C.a=4` and `--C.a='4'`.
        """
        rhs = os.path.expanduser(rhs)
        try:
            # Try to see if regular Python syntax will work. This
            # won't handle strings as the quote marks are removed
            # by the system shell.
            value = eval(rhs)
        except (NameError, SyntaxError):
            # This case happens if the rhs is a string.
            value = rhs

        exec(u'self.config.%s = value' % lhs)

    def _load_flag(self, cfg):
        """update self.config from a flag, which can be a dict or Config"""
        if isinstance(cfg, (dict, Config)):
            # don't clobber whole config sections, update
            # each section from config:
            for sec,c in iteritems(cfg):
                self.config[sec].update(c)
        else:
            raise TypeError("Invalid flag: %r" % cfg)

# raw --identifier=value pattern
# but *also* accept '-' as wordsep, for aliases
# accepts:  --foo=a
#           --Class.trait=value
#           --alias-name=value
# rejects:  -foo=value
#           --foo
#           --Class.trait
kv_pattern = re.compile(r'\-\-[A-Za-z][\w\-]*(\.[\w\-]+)*\=.*')

# just flags, no assignments, with two *or one* leading '-'
# accepts:  --foo
#           -foo-bar-again
# rejects:  --anything=anything
#           --two.word

flag_pattern = re.compile(r'\-\-?\w+[\-\w]*$')

class KeyValueConfigLoader(CommandLineConfigLoader):
    """A config loader that loads key value pairs from the command line.

    This allows command line options to be gives in the following form::

        ipython --profile="foo" --InteractiveShell.autocall=False
    """

    def __init__(self, argv=None, aliases=None, flags=None):
        """Create a key value pair config loader.

        Parameters
        ----------
        argv : list
            A list that has the form of sys.argv[1:] which has unicode
            elements of the form u"key=value". If this is None (default),
            then sys.argv[1:] will be used.
        aliases : dict
            A dict of aliases for configurable traits.
            Keys are the short aliases, Values are the resolved trait.
            Of the form: `{'alias' : 'Configurable.trait'}`
        flags : dict
            A dict of flags, keyed by str name. Vaues can be Config objects,
            dicts, or "key=value" strings.  If Config or dict, when the flag
            is triggered, The flag is loaded as `self.config.update(m)`.

        Returns
        -------
        config : Config
            The resulting Config object.

        Examples
        --------

            >>> from IPython.config.loader import KeyValueConfigLoader
            >>> cl = KeyValueConfigLoader()
            >>> d = cl.load_config(["--A.name='brian'","--B.number=0"])
            >>> sorted(d.items())
            [('A', {'name': 'brian'}), ('B', {'number': 0})]
        """
        self.clear()
        if argv is None:
            argv = sys.argv[1:]
        self.argv = argv
        self.aliases = aliases or {}
        self.flags = flags or {}


    def clear(self):
        super(KeyValueConfigLoader, self).clear()
        self.extra_args = []


    def _decode_argv(self, argv, enc=None):
        """decode argv if bytes, using stin.encoding, falling back on default enc"""
        uargv = []
        if enc is None:
            enc = DEFAULT_ENCODING
        for arg in argv:
            if not isinstance(arg, unicode_type):
                # only decode if not already decoded
                arg = arg.decode(enc)
            uargv.append(arg)
        return uargv


    def load_config(self, argv=None, aliases=None, flags=None):
        """Parse the configuration and generate the Config object.

        After loading, any arguments that are not key-value or
        flags will be stored in self.extra_args - a list of
        unparsed command-line arguments.  This is used for
        arguments such as input files or subcommands.

        Parameters
        ----------
        argv : list, optional
            A list that has the form of sys.argv[1:] which has unicode
            elements of the form u"key=value". If this is None (default),
            then self.argv will be used.
        aliases : dict
            A dict of aliases for configurable traits.
            Keys are the short aliases, Values are the resolved trait.
            Of the form: `{'alias' : 'Configurable.trait'}`
        flags : dict
            A dict of flags, keyed by str name. Values can be Config objects
            or dicts.  When the flag is triggered, The config is loaded as
            `self.config.update(cfg)`.
        """
        self.clear()
        if argv is None:
            argv = self.argv
        if aliases is None:
            aliases = self.aliases
        if flags is None:
            flags = self.flags

        # ensure argv is a list of unicode strings:
        uargv = self._decode_argv(argv)
        for idx,raw in enumerate(uargv):
            # strip leading '-'
            item = raw.lstrip('-')

            if raw == '--':
                # don't parse arguments after '--'
                # this is useful for relaying arguments to scripts, e.g.
                # ipython -i foo.py --matplotlib=qt -- args after '--' go-to-foo.py
                self.extra_args.extend(uargv[idx+1:])
                break

            if kv_pattern.match(raw):
                lhs,rhs = item.split('=',1)
                # Substitute longnames for aliases.
                if lhs in aliases:
                    lhs = aliases[lhs]
                if '.' not in lhs:
                    # probably a mistyped alias, but not technically illegal
                    warn.warn("Unrecognized alias: '%s', it will probably have no effect."%lhs)
                try:
                    self._exec_config_str(lhs, rhs)
                except Exception:
                    raise ArgumentError("Invalid argument: '%s'" % raw)

            elif flag_pattern.match(raw):
                if item in flags:
                    cfg,help = flags[item]
                    self._load_flag(cfg)
                else:
                    raise ArgumentError("Unrecognized flag: '%s'"%raw)
            elif raw.startswith('-'):
                kv = '--'+item
                if kv_pattern.match(kv):
                    raise ArgumentError("Invalid argument: '%s', did you mean '%s'?"%(raw, kv))
                else:
                    raise ArgumentError("Invalid argument: '%s'"%raw)
            else:
                # keep all args that aren't valid in a list,
                # in case our parent knows what to do with them.
                self.extra_args.append(item)
        return self.config

class ArgParseConfigLoader(CommandLineConfigLoader):
    """A loader that uses the argparse module to load from the command line."""

    def __init__(self, argv=None, aliases=None, flags=None, *parser_args, **parser_kw):
        """Create a config loader for use with argparse.

        Parameters
        ----------

        argv : optional, list
          If given, used to read command-line arguments from, otherwise
          sys.argv[1:] is used.

        parser_args : tuple
          A tuple of positional arguments that will be passed to the
          constructor of :class:`argparse.ArgumentParser`.

        parser_kw : dict
          A tuple of keyword arguments that will be passed to the
          constructor of :class:`argparse.ArgumentParser`.

        Returns
        -------
        config : Config
            The resulting Config object.
        """
        super(CommandLineConfigLoader, self).__init__()
        self.clear()
        if argv is None:
            argv = sys.argv[1:]
        self.argv = argv
        self.aliases = aliases or {}
        self.flags = flags or {}

        self.parser_args = parser_args
        self.version = parser_kw.pop("version", None)
        kwargs = dict(argument_default=argparse.SUPPRESS)
        kwargs.update(parser_kw)
        self.parser_kw = kwargs

    def load_config(self, argv=None, aliases=None, flags=None):
        """Parse command line arguments and return as a Config object.

        Parameters
        ----------

        args : optional, list
          If given, a list with the structure of sys.argv[1:] to parse
          arguments from. If not given, the instance's self.argv attribute
          (given at construction time) is used."""
        self.clear()
        if argv is None:
            argv = self.argv
        if aliases is None:
            aliases = self.aliases
        if flags is None:
            flags = self.flags
        self._create_parser(aliases, flags)
        self._parse_args(argv)
        self._convert_to_config()
        return self.config

    def get_extra_args(self):
        if hasattr(self, 'extra_args'):
            return self.extra_args
        else:
            return []

    def _create_parser(self, aliases=None, flags=None):
        self.parser = ArgumentParser(*self.parser_args, **self.parser_kw)
        self._add_arguments(aliases, flags)

    def _add_arguments(self, aliases=None, flags=None):
        raise NotImplementedError("subclasses must implement _add_arguments")

    def _parse_args(self, args):
        """self.parser->self.parsed_data"""
        # decode sys.argv to support unicode command-line options
        enc = DEFAULT_ENCODING
        uargs = [py3compat.cast_unicode(a, enc) for a in args]
        self.parsed_data, self.extra_args = self.parser.parse_known_args(uargs)

    def _convert_to_config(self):
        """self.parsed_data->self.config"""
        for k, v in iteritems(vars(self.parsed_data)):
            exec("self.config.%s = v"%k, locals(), globals())

class KVArgParseConfigLoader(ArgParseConfigLoader):
    """A config loader that loads aliases and flags with argparse,
    but will use KVLoader for the rest.  This allows better parsing
    of common args, such as `ipython -c 'print 5'`, but still gets
    arbitrary config with `ipython --InteractiveShell.use_readline=False`"""

    def _add_arguments(self, aliases=None, flags=None):
        self.alias_flags = {}
        # print aliases, flags
        if aliases is None:
            aliases = self.aliases
        if flags is None:
            flags = self.flags
        paa = self.parser.add_argument
        for key,value in iteritems(aliases):
            if key in flags:
                # flags
                nargs = '?'
            else:
                nargs = None
            if len(key) is 1:
                paa('-'+key, '--'+key, type=unicode_type, dest=value, nargs=nargs)
            else:
                paa('--'+key, type=unicode_type, dest=value, nargs=nargs)
        for key, (value, help) in iteritems(flags):
            if key in self.aliases:
                #
                self.alias_flags[self.aliases[key]] = value
                continue
            if len(key) is 1:
                paa('-'+key, '--'+key, action='append_const', dest='_flags', const=value)
            else:
                paa('--'+key, action='append_const', dest='_flags', const=value)

    def _convert_to_config(self):
        """self.parsed_data->self.config, parse unrecognized extra args via KVLoader."""
        # remove subconfigs list from namespace before transforming the Namespace
        if '_flags' in self.parsed_data:
            subcs = self.parsed_data._flags
            del self.parsed_data._flags
        else:
            subcs = []

        for k, v in iteritems(vars(self.parsed_data)):
            if v is None:
                # it was a flag that shares the name of an alias
                subcs.append(self.alias_flags[k])
            else:
                # eval the KV assignment
                self._exec_config_str(k, v)

        for subc in subcs:
            self._load_flag(subc)

        if self.extra_args:
            sub_parser = KeyValueConfigLoader()
            sub_parser.load_config(self.extra_args)
            self.config.merge(sub_parser.config)
            self.extra_args = sub_parser.extra_args


def load_pyconfig_files(config_files, path):
    """Load multiple Python config files, merging each of them in turn.

    Parameters
    ==========
    config_files : list of str
        List of config files names to load and merge into the config.
    path : unicode
        The full path to the location of the config files.
    """
    config = Config()
    for cf in config_files:
        loader = PyFileConfigLoader(cf, path=path)
        try:
            next_config = loader.load_config()
        except ConfigFileNotFound:
            pass
        except:
            raise
        else:
            config.merge(next_config)
    return config