[web] Fix duplicate dep, strengthen provisioning.

web/web.py

 #!/usr/bin/env python
 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Manages web/ resource checkout and building.
 
 This script can be run in one of three modes:
   - As "initialize.py", it will perform resource dependency checkout for
     "luci_deploy" and quit.
   - As "build.py", it will build web apps to a "luci_deploy" directory.
   - As "web.py", it is a user-facing tool to manually build web components.
 """
 
 import argparse
+import itertools
 import logging
 import os
 import pipes
+import shutil
 import subprocess
 import sys
 
 from distutils.spawn import find_executable
 
 LOGGER = logging.getLogger('web.py')
 
 # The root of the "luci-go" checkout, relative to the current "build.py" file.
 _LUCI_GO_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
@@ skipping 27 matching lines @@
       raise Exception('Unable to locate Node.js installation.')
     tc = cls(web_dir, *node_js)
 
     # Install NPM deps from "package.json".
     def install_npm_deps():
       tc.npm('install', cwd=web_dir)
     cls._call_if_outdated(
         install_npm_deps,
         os.path.join(web_dir, '.npm.installed'),
         os.path.join(web_dir, 'package.json'),
+        [os.path.join(web_dir, 'node_modules')],
         force)
 
     # Install Bower deps from "bower.json".
     def install_bower_deps():
       tc.bower('install', cwd=web_dir)
     cls._call_if_outdated(
         install_bower_deps,
         os.path.join(web_dir, '.bower.installed'),
         os.path.join(web_dir, 'bower.json'),
+        [os.path.join(web_dir, 'inc', 'bower_components')],
         force)
 
     return tc
 
   @staticmethod
-  def _call_if_outdated(fn, manifest_path, defs_path, force):
+  def _call_if_outdated(fn, manifest_path, defs_path, clean_paths, force):
     """Will call "fn" if the file at "install_path" doesn't match "spec".
 
     If "fn" completes without raising an exception, the "spec" file will be
     copied to the "installed" path, making subsequent runs of this function a
     no-op until the spec file changes..
 
     Args:
       fn (callable): The function to call if they don't match.
       manifest_path (str): The path to the installed state file.
       defs_path (str): The path to the source spec file.
+      clean_paths (list): Path of destination files and directories to clean on
+          reprovision.
       force (bool): If true, call the function regardless.
     """
     with open(defs_path, 'r') as fd:
       spec_data = fd.read()
 
     if not force and os.path.isfile(manifest_path):
       with open(manifest_path, 'r') as fd:
         current = fd.read()
       if spec_data == current:
         return
 
+    # Clean all paths.
+    for path in itertools.chain(clean_paths, (manifest_path,)):
+      if os.path.isdir(path):
+        LOGGER.info('Purging directory on reprovision: %r', path)
+        shutil.rmtree(path)
+      elif os.path.isfile(path):
+        LOGGER.info('Purging file on reprovision: %r', path)
+        os.remove(path)
+
     # Either forcing or out of date.
     fn()
 
     # Update our installed file to match our spec data.
     with open(manifest_path, 'w') as fd:
       fd.write(spec_data)
 
   @property
   def web_dir(self):
     return self._web_dir
@@ skipping 161 matching lines @@
     return _main_initialize(args)
   elif script_name == 'build.py':
     return _main_deploy(args)
   else:
     return _main(args)
 
 
 if __name__ == '__main__':
   logging.basicConfig(level=logging.INFO)
   sys.exit(main(sys.argv))