104 lines
4 KiB
Text
104 lines
4 KiB
Text
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.. default-role:: literal
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Config API Details
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==================
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:module: :api:`config.py`
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:test cases: - :api:`test_config_api.py`
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- :api:`test_config_big_example.py`
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The handling of options is split into two parts: the description of
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which options are available, what their possible values and defaults are
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and how they are organized into a tree. A specific choice of options is
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bundled into a configuration object which has a reference to its option
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description (and therefore makes sure that the configuration values
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adhere to the option description).
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The configuration object
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-------------------------
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:api:`config.Config()` object that lives in :api:`config.py` hold the
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choosen values for the options (or the default value for the
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:api:`option.Option()` object, if no choice was made).
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A `Config` object is informed by an :api:`option.OptionDescription`
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instance. The attributes of the ``Config`` objects are the names of the
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children of the ``OptionDescription``.
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Here are the (useful) methods on ``Config``:
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:api:`config.Config.__init__(self, descr, **overrides)`:
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``descr`` is an instance of :api:`option.OptionDescription` that
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describes the configuration object. ``override`` can be used to
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set different default values (see method ``override``).
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:api:`config.Config.override(self, overrides)`:
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override default values. This marks the overridden values as defaults.
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``overrides`` is a dictionary of path strings to values.
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:api:`config.Config.set(self, **kwargs)`:
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"do what I mean"-interface to option setting. Searches all paths
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starting from that config for matches of the optional arguments
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and sets the found option if the match is not ambiguous.
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:api:`config.Config.get(self, name)`:
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the behavior is much like the attribute access way, except that
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the search for the option is performed recursively in the whole
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configuration tree.
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:api:`config.Config.cfgimpl_read_write()`:
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configuration level `read_write` status, see :doc:`status`
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:api:`config.Config.cfgimpl_read_only()`:
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configuration level `read_only` status, see :doc:`status`
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Here are some private attributes of a `Config()` object, for a
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comprehension of the internal merchanism:
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- `_cfgimpl_descr =` :api:`option.OptionDescription()`,
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e.g. the :ref:`optionapi#schema`
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- `_cfgimpl_values` contains the :api:`option.Option()`'s values.
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Yes, the values of the options: remember that the values are stored **inside**
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the :api:`config.Config()` and not in the `Option()`
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`_cfgimpl_values` contains something like that
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::
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{'int': 0, 'wantframework': False, 'objspace': 'std', 'bool': False,
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'str': 'abc', 'gc': <config.Config object at 0xa33f8ec>, 'wantref': False}
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We can see that values can also be config objects, it's the
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sub-namespaces that are stored in the values as `Config()` objects.
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convenience utilities (iteration, exports...)
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-----------------------------------------------
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With this :api:`config.Config()` configuration management entry point,
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it is possible to
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- `iter` on config, notice that there is an iteration order wich is
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the order of the :ref:`optionapi#schema` specification entries,
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- compare two configs (equality),
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- export the whole config into a `dict` with :api:`config.make_dict()`,
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- `validate()` an option value into a config, see :doc:`consistency`.
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:api:`option.Option()` objects in a config are iterable in the pythonic
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way, that is something like `[(name, value) for name, value in config]`.
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To iter on groups in the same manner, use the
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:api:`config.Config.iter_groups()` method wich yields generators too.
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**iteration utilities**
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:api:`config.Config.__iter__()`
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Pythonesque way of parsing group's ordered options.
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:api:`config.Config.iter_groups(group_type=None)`:
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To iter on groups objects only.
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All groups are returned if `group_type` is `None`, otherwise the groups
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can be filtered by categories (families, or whatever).
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