Mypal/python/mach/docs/settings.rst

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.. _mach_settings:
========
Settings
========
Mach can read settings in from a set of configuration files. These
configuration files are either named ``machrc`` or ``.machrc`` and
are specified by the bootstrap script. In mozilla-central, these files
can live in ``~/.mozbuild`` and/or ``topsrcdir``.
Settings can be specified anywhere, and used both by mach core or
individual commands.
Core Settings
=============
These settings are implemented by mach core.
* alias - Create a command alias. This is useful if you want to alias a command to something else, optionally including some defaults. It can either be used to create an entire new command, or provide defaults for an existing one. For example:
.. parsed-literal::
[alias]
mochitest = mochitest -f browser
browser-test = mochitest -f browser
Defining Settings
=================
Settings need to be explicitly defined, along with their type,
otherwise mach will throw when trying to access them.
To define settings, use the :func:`~decorators.SettingsProvider`
decorator in an existing mach command module. E.g:
.. code-block:: python
from mach.decorators import SettingsProvider
@SettingsProvider
class ArbitraryClassName(object):
config_settings = [
('foo.bar', 'string'),
('foo.baz', 'int', 0, set([0,1,2])),
]
``@SettingsProvider``'s must specify a variable called ``config_settings``
that returns a list of tuples. Alternatively, it can specify a function
called ``config_settings`` that returns a list of tuples.
Each tuple is of the form:
.. code-block:: python
('<section>.<option>', '<type>', default, extra)
``type`` is a string and can be one of:
string, boolean, int, pos_int, path
``default`` is optional, and provides a default value in case none was
specified by any of the configuration files.
``extra`` is also optional and is a dict containing additional key/value
pairs to add to the setting's metadata. The following keys may be specified
in the ``extra`` dict:
* ``choices`` - A set of allowed values for the setting.
Wildcards
---------
Sometimes a section should allow arbitrarily defined options from the user, such
as the ``alias`` section mentioned above. To define a section like this, use ``*``
as the option name. For example:
.. parsed-literal::
('foo.*', 'string')
This allows configuration files like this:
.. parsed-literal::
[foo]
arbitrary1 = some string
arbitrary2 = some other string
Documenting Settings
====================
All settings must at least be documented in the en_US locale. Otherwise,
running ``mach settings`` will raise. Mach uses gettext to perform localization.
A handy command exists to generate the localization files:
.. parsed-literal::
mach settings locale-gen <section>
You'll be prompted to add documentation for all options in section with the
en_US locale. To add documentation in another locale, pass in ``--locale``.
Accessing Settings
==================
Now that the settings are defined and documented, they're accessible from
individual mach commands if the command receives a context in its constructor.
For example:
.. code-block:: python
from mach.decorators import (
Command,
CommandProvider,
SettingsProvider,
)
@SettingsProvider
class ExampleSettings(object):
config_settings = [
('a.b', 'string', 'default'),
('foo.bar', 'string'),
('foo.baz', 'int', 0, {'choices': set([0,1,2])}),
]
@CommandProvider
class Commands(object):
def __init__(self, context):
self.settings = context.settings
@Command('command', category='misc',
description='Prints a setting')
def command(self):
print(self.settings.a.b)
for option in self.settings.foo:
print(self.settings.foo[option])