126 lines
4.4 KiB
Python
126 lines
4.4 KiB
Python
from collections import OrderedDict, namedtuple
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try:
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# Python 2
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from ConfigParser import RawConfigParser
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except ImportError:
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# Python 3
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from configparser import RawConfigParser
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Section_format = namedtuple('Section_format', ('name', 'options'))
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Config_option = namedtuple('Config_option', ('name', 'value_type', 'required'))
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def option(name, value_type=str, required=True):
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'''
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Given a config file option name, an expected type for its value, and whether it's required,
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return a Config_option capturing that information.
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'''
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return Config_option(name, value_type, required)
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def validate_configuration_format(parser, config_format):
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'''
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Given an open RawConfigParser and an expected config file format, validate that the parsed
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configuration file has the expected sections, that any required options are present in those
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sections, and that there aren't any unexpected options.
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A section is required if any of its contained options are required.
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Raise ValueError if anything is awry.
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'''
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section_names = set(parser.sections())
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required_section_names = tuple(
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section.name for section in config_format
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if any(option.required for option in section.options)
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)
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unknown_section_names = section_names - set(
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section_format.name for section_format in config_format
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)
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if unknown_section_names:
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raise ValueError(
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'Unknown config sections found: {}'.format(', '.join(unknown_section_names))
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)
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missing_section_names = set(required_section_names) - section_names
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if missing_section_names:
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raise ValueError(
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'Missing config sections: {}'.format(', '.join(missing_section_names))
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)
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for section_format in config_format:
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if section_format.name not in section_names:
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continue
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option_names = parser.options(section_format.name)
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expected_options = section_format.options
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unexpected_option_names = set(option_names) - set(option.name for option in expected_options)
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if unexpected_option_names:
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raise ValueError(
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'Unexpected options found in config section {}: {}'.format(
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section_format.name,
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', '.join(sorted(unexpected_option_names)),
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)
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)
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missing_option_names = tuple(
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option.name for option in expected_options if option.required
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if option.name not in option_names
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)
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if missing_option_names:
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raise ValueError(
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'Required options missing from config section {}: {}'.format(
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section_format.name,
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', '.join(missing_option_names)
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)
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)
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def parse_section_options(parser, section_format):
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'''
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Given an open RawConfigParser and an expected section format, return the option values from that
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section as a dict mapping from option name to value. Omit those options that are not present in
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the parsed options.
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Raise ValueError if any option values cannot be coerced to the expected Python data type.
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'''
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type_getter = {
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str: parser.get,
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int: parser.getint,
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}
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return OrderedDict(
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(option.name, type_getter[option.value_type](section_format.name, option.name))
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for option in section_format.options
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if parser.has_option(section_format.name, option.name)
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)
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def parse_configuration(config_filename, config_format):
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'''
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Given a config filename and an expected config file format, return the parsed configuration
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as a namedtuple with one attribute for each parsed section.
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Raise IOError if the file cannot be read, or ValueError if the format is not as expected.
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'''
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parser = RawConfigParser()
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if not parser.read(config_filename):
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raise ValueError('Configuration file cannot be opened: {}'.format(config_filename))
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validate_configuration_format(parser, config_format)
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# Describes a parsed configuration, where each attribute is the name of a configuration file
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# section and each value is a dict of that section's parsed options.
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Parsed_config = namedtuple('Parsed_config', (section_format.name for section_format in config_format))
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return Parsed_config(
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*(
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parse_section_options(parser, section_format)
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for section_format in config_format
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)
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)
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