Devtools: refactor shell configuration logic.

mojo/devtools/common/devtoolslib/paths.py

 # Copyright 2015 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.
 
 """Supports inferring locations of files in default checkout layouts.
 
 These functions allow devtools scripts to work out-of-the-box with regular Mojo
 checkouts.
 """
 
+import collections
 import os.path
 import sys
 
 
 def find_ancestor_with(relpath):
   """Returns the lowest ancestor of this file that contains |relpath|."""
   cur_dir_path = os.path.abspath(os.path.dirname(__file__))
   while True:
     if os.path.exists(os.path.join(cur_dir_path, relpath)):
       return cur_dir_path
 
     next_dir_path = os.path.dirname(cur_dir_path)
     if next_dir_path != cur_dir_path:
       cur_dir_path = next_dir_path
     else:
       return None
 
 
-def infer_mojo_paths(is_android, is_debug, target_cpu):
-  """Infers the locations of select build output artifacts in a regular Mojo
-  checkout.
+def infer_paths(is_android, is_debug, target_cpu):
+  """Infers the locations of select build output artifacts in a regular
+  Chromium-like checkout. This should grow thinner or disappear as we introduce
+  per-repo config files, see https://github.com/domokit/devtools/issues/28.
 
   Returns:
-    Tuple of path dictionary, error message. Only one of the two will be
-    not-None.
+    Defaultdict with the inferred paths.
   """
   build_dir = (('android_' if is_android else '') +
                (target_cpu + '_' if target_cpu else '') +
                ('Debug' if is_debug else 'Release'))
   out_build_dir = os.path.join('out', build_dir)
 
   root_path = find_ancestor_with(out_build_dir)
+  paths = collections.defaultdict(lambda: None)
   if not root_path:
-    return None, ('Failed to find build directory: ' + out_build_dir)
+    return paths
 
-  paths = {}
-  paths['root'] = root_path
   build_dir_path = os.path.join(root_path, out_build_dir)
-  paths['build'] = build_dir_path
+  paths['build_dir_path'] = build_dir_path
   if is_android:
-    paths['shell'] = os.path.join(build_dir_path, 'apks', 'MojoShell.apk')
-    paths['adb'] = os.path.join(root_path, 'third_party', 'android_tools',
+    paths['shell_path'] = os.path.join(build_dir_path, 'apks', 'MojoShell.apk')
+    paths['adb_path'] = os.path.join(root_path, 'third_party', 'android_tools',
                                 'sdk', 'platform-tools', 'adb')
   else:
-    paths['shell'] = os.path.join(build_dir_path, 'mojo_shell')
-  return paths, None
+    paths['shell_path'] = os.path.join(build_dir_path, 'mojo_shell')
+  return paths
 
 
 # Based on Chromium //tools/find_depot_tools.py.
 def find_depot_tools():
   """Searches for depot_tools.
 
   Returns:
     Path to the depot_tools checkout present on the machine, None if not found.
   """
   def _is_real_depot_tools(path):
@@ skipping 10 matching lines @@
   # Rare case, it's not even in PATH, look upward up to root.
   root_dir = os.path.dirname(os.path.abspath(__file__))
   previous_dir = os.path.abspath(__file__)
   while root_dir and root_dir != previous_dir:
     i = os.path.join(root_dir, 'depot_tools')
     if _is_real_depot_tools(i):
       return i
     previous_dir = root_dir
     root_dir = os.path.dirname(root_dir)
   return None