[cr tool] Make context implicit

tools/cr/main.py

 # 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.
 
 """Chromium cr tool main module.
 
 Holds the main function and all it's support code.
 """
 
 import os
 import sys
 import cr
 import cr.auto.user
 import cr.autocomplete
 import cr.loader
+import cr.base.context
 
 _CONTACT = 'iancottrell@chromium.org'
 
 
 def Main():
   """Chromium cr tool main function.
 
   This is the main entry point of the cr tool, it finds and loads all the
   plugins, creates the context and then activates and runs the specified
   command.
   """
 
   # Add the users plugin dir to the cr.auto.user package scan
   user_path = os.path.expanduser(os.path.join('~', '.config', 'cr'))
   cr.auto.user.__path__.append(user_path)
 
   cr.loader.Scan()
 
   # Build the command context
-  context = cr.Context(
+  with cr.base.context.Create(
       description='The chrome dev build tool.',
       epilog='Contact ' + _CONTACT + ' if you have issues with this tool.',
-  )
-  # Install the sub-commands
-  for command in cr.Command.Plugins():
-    context.AddSubParser(command)
+      ) as context:
 
-  # test for the special autocomplete command
-  if context.autocompleting:
-    # After plugins are loaded so pylint: disable=g-import-not-at-top
-    cr.autocomplete.Complete(context)
-    return
-  # Speculative argument processing to add config specific args
-  context.ParseArgs(True)
-  cr.plugin.Activate(context)
-  # At this point we should know what command we are going to use
-  command = cr.Command.GetActivePlugin(context)
-  # Do some early processing, in case it changes the build dir
-  if command:
-    command.EarlyArgProcessing(context)
-  # Update the activated set again, in case the early processing changed it
-  cr.plugin.Activate(context)
-  # Load the build specific configuration
-  found_build_dir = cr.base.client.LoadConfig(context)
-  # Final processing or arguments
-  context.ParseArgs()
-  cr.plugin.Activate(context)
-  # If we did not get a command before, it might have been fixed.
-  if command is None:
-    command = cr.Command.GetActivePlugin(context)
-  # If the verbosity level is 3 or greater, then print the environment here
-  if context.verbose >= 3:
-    context.DumpValues(context.verbose > 3)
-  if command is None:
-    print context.Substitute('No command specified.')
-    exit(1)
-  if command.requires_build_dir:
-    if not found_build_dir:
-      if not context.Find('CR_OUT_FULL'):
-        print context.Substitute(
-            'No build directory specified. Please use cr init to make one.')
-      else:
-        print context.Substitute(
-            'Build {CR_BUILD_DIR} not a valid build directory')
+    # Try to detect the current client information
+    cr.base.client.DetectClient()
+
+    # Install the sub-commands
+    for command in cr.Command.Plugins():
+      cr.context.AddSubParser(command)
+
+    # test for the special autocomplete command
+    if cr.context.autocompleting:
+      # After plugins are loaded so pylint: disable=g-import-not-at-top
+      cr.autocomplete.Complete()
+      return
+    # Speculative argument processing to add config specific args
+    cr.context.ParseArgs(True)
+    cr.plugin.Activate()
+    # At this point we should know what command we are going to use
+    command = cr.Command.GetActivePlugin()
+    # Do some early processing, in case it changes the build dir
+    if command:
+      command.EarlyArgProcessing()
+    # Update the activated set again, in case the early processing changed it
+    cr.plugin.Activate()
+    # Load the build specific configuration
+    found_build_dir = cr.base.client.LoadConfig()
+    # Final processing or arguments
+    cr.context.ParseArgs()
+    cr.plugin.Activate()
+    # If we did not get a command before, it might have been fixed.
+    if command is None:
+      command = cr.Command.GetActivePlugin()
+    # If the verbosity level is 3 or greater, then print the environment here
+    if cr.context.verbose >= 3:
+      cr.context.DumpValues(cr.context.verbose > 3)
+    if command is None:
+      print cr.context.Substitute('No command specified.')
       exit(1)
-    if context.Find('CR_VERSION') != cr.base.client.VERSION:
-      print context.Substitute(
-          'Build {CR_BUILD_DIR} is for the wrong version of cr')
-      print 'Please run cr init to reset it'
-      exit(1)
-    cr.Platform.Prepare(context)
-  if context.verbose >= 1:
-    print context.Substitute(
-        'Running cr ' + command.name + ' for {CR_BUILD_DIR}')
-  # Invoke the given command
-  command.Run(context)
+    if command.requires_build_dir:
+      if not found_build_dir:
+        if not cr.context.Find('CR_OUT_FULL'):
+          print cr.context.Substitute(
+              'No build directory specified. Please use cr init to make one.')
+        else:
+          print cr.context.Substitute(
+              'Build {CR_BUILD_DIR} not a valid build directory')
+        exit(1)
+      if cr.context.Find('CR_VERSION') != cr.base.client.VERSION:
+        print cr.context.Substitute(
+            'Build {CR_BUILD_DIR} is for the wrong version of cr')
+        print 'Please run cr init to reset it'
+        exit(1)
+      cr.Platform.Prepare()
+    if cr.context.verbose >= 1:
+      print cr.context.Substitute(
+          'Running cr ' + command.name + ' for {CR_BUILD_DIR}')
+    # Invoke the given command
+    command.Run()
 
 if __name__ == '__main__':
   sys.exit(Main())