Value Interpolation

[jbasko]

• We don't want globally enabled value interpolation.

• [ ] When sending an interpolation-enabled value to a persistence adapter, we must send "raw" value, not the interpolated value. Perhaps raw_str_value can be used for this.

• [ ] Allow user to enable ConfigParser-like value interpolation if they are using ConfigParser to load a file, but it is up to ConfigParser what actually happens there. If user relies on that, let it be.

config = Config('defaults.ini')
config.configparser.load('config.ini', interpolation_enabled=True)

• [ ] Our own value interpolation which is enabled per item or section with some special attribute. Ideally it would be limited to the item's siblings. And use basic python string formatting?
• References to other sections should not be supported because that would complicate format strings and also increase the number of names passed to format(), and put unnecessary pressure on loading order of sections.

config = Config({
    'uploads': {
        'base_dir': '/opt/uploads-service',
        'tmp_dir': '{base_dir}/tmp',
    }
}, interpolation_enabled=True)

assert config.uploads.tmp_dir.value == '/opt/uploads-service/tmp'

[jbasko]

Value interpolation won't be supported for the time being. It complicates everything.