Cleanup machine based on the state in configuration file for mini installer test.

chrome/test/mini_installer/visitor_runner.py

+# Copyright 2017 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.
+
+import re
+
+import file_visitor
+import process_visitor
+import registry_visitor
+
+class VisitorRunner(object):
+  """Run all visitor based on a state's property dictionary.
+
+     A property dictionary is a dictionary where each key is a verifier's name
+     and the associated value is the input to that verifier. For details about
+     the input format for each verifier, take a look at http://goo.gl/1P85WL
+
+     All visitor's name should match the name of property. For example, visitor
+     for property "RegistryEntries" will be "registry_entries_visitor".
+  """
+  def __init__(self):
+    self._property_name_match = {}
+
+  def Run(self, state):
+    """ Walk through all properties of the state.
+
+        Args:
+          state: A property dictionary belongs to a state.
+    """
+    for property_name, property_value in state.iteritems():
+      visitor_name = self._Convert(property_name) + '_visitor'

[grt (UTC plus 2), 2017/03/15 09:00:08]

i don't understand this part -- why is there a per-type visitor? in a typical
visitor pattern, the visitor interface has a virtual method for each "thing"
being visited. there's no magic in finding which visitor to invoke -- there's
just one visitor to which each "thing" is dispatched.

+      if not hasattr(self, visitor_name):
+        self._HandleInvalidProperty(property_name)
+      else:
+        getattr(self, visitor_name).Traverse(property_value)
+
+
+
+  def _HandleInvalidProperty(self, property_name):
+    """ Abstract class.
+
+        Handle the situation that the property in config file does not supported
+        by the runner.
+
+        Args:
+          property_name: A string represents the unsupported property's name.
+    """
+    pass
+
+  def _Convert(self, input_str):
+    """Convert CamelCase property name in config file into snake_case for
+      reflection
+    """
+    if input_str not in self._property_name_match:
+      output_str = re.sub('([A-Z][a-z]*)', r'_\1', input_str).lower()[1:]
+      self._property_name_match[input_str] = output_str
+    return self._property_name_match[input_str]
+
+
+class VerifierRunner(VisitorRunner):
+  """Run all verifing visitor to verify that the current machine states match
+     the property dictionary.
+  """
+
+  def __init__(self, variable_expander):
+    """Constructor."""
+    # TODO(sukolsak): Implement other verifiers
+    super(VerifierRunner, self).__init__()
+    self.files_visitor = file_visitor.FileVerifier(variable_expander)
+    self.registry_entries_visitor = registry_visitor.RegistryVerifier(
+        variable_expander)
+    self.processes_visitor = process_visitor.ProcessVerifier(variable_expander)
+
+  def _HandleInvalidProperty(self, property_name):
+    """ Overridden VisitorRunner._HandleInvalidProperty, unsupported
+        property raises KeyError.
+    """
+    raise KeyError('Unknown verifier %s' % property_name)
+
+
+class CleanupRunner(VisitorRunner):
+  """ Run all cleaning visitor based on the config state to reset the machine to
+      a clean state.
+
+      Only support:
+          1) Delete directory, always recursively. Delete file is NOT supported.
+          2) Delete registry key, always recursively.
+  """
+
+  _instance = None
+
+  def __init__(self, variable_expander):
+    """Constructor."""
+    # TODO(sukolsak): Implement other verifiers
+    super(CleanupRunner, self).__init__()
+    self.files_visitor = file_visitor.FileCleaner(variable_expander)
+    self.registry_entries_visitor = registry_visitor.RegistryCleaner(
+        variable_expander)
+
+
+  @classmethod
+  def Create(cls, variable_expander):
+    """Singleton constructor.
+    """
+    if not cls._instance:
+      cls._instance = CleanupRunner(variable_expander)
+    return cls._instance
+
+  def _HandleInvalidProperty(self, property_name):
+    """ Overridden VisitorRunner._HandleInvalidProperty, ignore unsupported
+        state's property.
+    """
+    return