Bug 808336 - Part 2: Discover mach settings providers via decorators; r=jhammel

With this patch, mach is now decoupled from the build system and is
truly a generic command dispatching framework.

mach

@@ -39,6 +39,7 @@ SEARCH_PATHS = [
 MACH_MODULES = [
     'layout/tools/reftest/mach_commands.py',
     'python/mozboot/mozboot/mach_commands.py',
+    'python/mozbuild/mozbuild/config.py',
     'testing/mochitest/mach_commands.py',
     'testing/xpcshell/mach_commands.py',
 ]

python/mach/mach/decorators.py

@@ -8,6 +8,7 @@ import inspect
 import types
 
 from .base import MethodHandler
+from .config import ConfigProvider
 from .registrar import Registrar
 
 
@@ -111,3 +112,21 @@ class CommandArgument(object):
         func._mach_command_args = command_args
 
         return func
+
+def SettingsProvider(cls):
+    """Class decorator to denote that this class provides Mach settings.
+
+    When this decorator is encountered, the underlying class will automatically
+    be registered with the Mach registrar and will (likely) be hooked up to the
+    mach driver.
+
+    This decorator is only allowed on mach.config.ConfigProvider classes.
+    """
+    if not issubclass(cls, ConfigProvider):
+        raise Exception('@SettingsProvider encountered on class that does ' +
+                        'not derived from mach.config.ConfigProvider.')
+
+    Registrar.register_settings_provider(cls)
+
+    return cls
+

python/mach/mach/main.py

@@ -17,8 +17,6 @@ import traceback
 import uuid
 import sys
 
-from mozbuild.base import BuildConfig
-
 from .base import CommandContext
 
 from .decorators import (
@@ -33,12 +31,6 @@ from .logging import LoggingManager
 from .registrar import Registrar
 
 
-# Classes inheriting from ConfigProvider that provide settings.
-# TODO this should come from auto-discovery somehow.
-SETTINGS_PROVIDERS = [
-    BuildConfig,
-]
-
 # Settings for argument parser that don't get proxied to sub-module. i.e. these
 # are things consumed by the driver itself.
 CONSUMED_ARGUMENTS = [
@@ -412,7 +404,7 @@ To see more help for a specific command, run:
         self.settings = None
         return False
 
-        for provider in SETTINGS_PROVIDERS:
+        for provider in Registrar.settings_providers:
             provider.register_settings()
             self.settings.register_provider(provider)
 

python/mach/mach/registrar.py

@@ -12,12 +12,16 @@ class MachRegistrar(object):
 
     def __init__(self):
         self.command_handlers = {}
+        self.settings_providers = set()
 
     def register_command_handler(self, handler):
         name = handler.parser_args[0][0]
 
         self.command_handlers[name] = handler
 
+    def register_settings_provider(self, cls):
+        self.settings_providers.add(cls)
+
     def populate_argument_parser(self, parser):
         for command in sorted(self.command_handlers.keys()):
             handler = self.command_handlers[command]

python/mozbuild/mozbuild/base.py

@@ -5,7 +5,6 @@
 from __future__ import unicode_literals
 
 import logging
-import multiprocessing
 import os
 import pymake.parser
 import subprocess
@@ -14,14 +13,11 @@ import which
 
 from pymake.data import Makefile
 
-from mach.config import (
-    ConfigProvider,
-    PositiveIntegerType,
-)
-
 from mach.mixin.logging import LoggingMixin
 from mach.mixin.process import ProcessExecutionMixin
 
+from .config import BuildConfig
+
 
 class MozbuildObject(ProcessExecutionMixin):
     """Base class providing basic functionality useful to many modules.
@@ -282,22 +278,6 @@ class MozbuildObject(ProcessExecutionMixin):
             topobjdir=self.topobjdir)
 
 
-class BuildConfig(ConfigProvider):
-    """The configuration for mozbuild."""
-
-    def __init__(self, settings):
-        self.settings = settings
-
-    @classmethod
-    def _register_settings(cls):
-        def register(section, option, type_cls, **kwargs):
-            cls.register_setting(section, option, type_cls, domain='mozbuild',
-                **kwargs)
-
-        register('build', 'threads', PositiveIntegerType,
-            default=multiprocessing.cpu_count())
-
-
 class MachCommandBase(MozbuildObject):
     """Base class for mach command providers that wish to be MozbuildObjects.
 

python/mozbuild/mozbuild/config.py

@@ -0,0 +1,33 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import unicode_literals
+
+import multiprocessing
+
+from mach.config import (
+    ConfigProvider,
+    PositiveIntegerType,
+)
+
+from mach.decorators import SettingsProvider
+
+
+@SettingsProvider
+class BuildConfig(ConfigProvider):
+    """The configuration for mozbuild."""
+
+    def __init__(self, settings):
+        self.settings = settings
+
+    @classmethod
+    def _register_settings(cls):
+        def register(section, option, type_cls, **kwargs):
+            cls.register_setting(section, option, type_cls, domain='mozbuild',
+                **kwargs)
+
+        register('build', 'threads', PositiveIntegerType,
+            default=multiprocessing.cpu_count())
+
+