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:
[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 SettingsProvider()
decorator in an existing mach command module. E.g:
from mach.decorators import SettingsProvider
from mozbuild.base import MachCommandBase
@SettingsProvider
class ArbitraryClassName(MachCommandBase):
config_settings = [
('foo.bar', 'string', "A helpful description"),
('foo.baz', 'int', "Another description", 0, {'choices': 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:
('<section>.<option>', '<type>', '<description>', default, extra)
type
is a string and can be one of:
string, boolean, int, pos_int, path
description
is a string explaining how to define the settings and
where they get used. Descriptions should ideally be multi-line paragraphs
where the first line acts as a short description.
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:
('foo.*', 'string', 'desc')
This allows configuration files like this:
[foo]
arbitrary1 = some string
arbitrary2 = some other string
Finding Settings¶
You can see which settings are available as well as their description and expected values by running:
./mach settings # or
./mach settings --list
Accessing Settings¶
Now that the settings are defined and documented, they’re accessible from individual mach commands from the mach command context. For example:
from mach.decorators import (
Command,
SettingsProvider,
)
from mozbuild.base import MachCommandBase
@SettingsProvider
class ExampleSettings(object):
config_settings = [
('a.b', 'string', 'desc', 'default'),
('foo.bar', 'string', 'desc',),
('foo.baz', 'int', 'desc', 0, {'choices': set([0,1,2])}),
]
@Command('command', category='misc',
description='Prints a setting')
def command(command_context):
settings = command_context._mach_context.settings
print(settings.a.b)
for option in settings.foo:
print(settings.foo[option])