Adding base class for cr actions

BUG=316397

Review URL: https://codereview.chromium.org/79523002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236517 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 59 insertions, 0 deletions

diff --git a/tools/cr/cr/actions/__init__.py b/tools/cr/cr/actions/__init__.py
new file mode 100644
index 0000000..5f818b3
--- /dev/null
+++ b/tools/cr/cr/actions/__init__.py
@@ -0,0 +1,10 @@
+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""A package to hold all the actions for the cr tool.
+
+This package holds the standard actions used by the commands in the cr tool.
+These actions are the things that actually perform the work, they are generally
+run in sequences by commands.
+"""
diff --git a/tools/cr/cr/actions/action.py b/tools/cr/cr/actions/action.py
new file mode 100644
index 0000000..b812aae
--- /dev/null
+++ b/tools/cr/cr/actions/action.py
@@ -0,0 +1,49 @@
+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""A module for the Action plugin base class."""
+
+import cr
+
+
+class Action(cr.Plugin):
+  """Base class for cr actions.
+
+  This provides the standard interface used to add actions to commands,
+  including support for selecting the right implementation of an action and
+  handling command line arguments for the action.
+  """
+
+  @classmethod
+  def AddArguments(cls, command, parser):
+    cls.AddSelectorArg(command, parser)
+
+  @classmethod
+  def AddSelectorArg(cls, command, parser):
+    parser.add_argument(
+        cls.SELECTOR_ARG, dest=cls.SELECTOR,
+        choices=cls.Choices(),
+        default=None,
+        help=cls.SELECTOR_HELP + 'Overrides ' + cls.SELECTOR
+    )
+
+  @cr.Plugin.activemethod
+  def Skipping(self, context):
+    """A method that is used to detect void or skip implementations.
+
+    Most actions have a skip version that you can select to indicate that you
+    want to not perform the action at all.
+    It is important that commands can detect this so they can modify the action
+    sequence if there are other changes that depend on it (for instance not
+    performing actions that were only there to produce the inputs of an action
+    that is being skipped).
+
+    Args:
+      context: the cr context to test within.
+    Returns:
+      True if this implementation is a skip action.
+    """
+    return self.name == 'skip'
+
+