New run shell implementation for DeviceUtils

build/android/pylib/device/device_utils.py

Index: build/android/pylib/device/device_utils.py
diff --git a/build/android/pylib/device/device_utils.py b/build/android/pylib/device/device_utils.py
index 75b2ae06ced358d9863cdda2c5a383cdf6e5298b..5d04a22135221d0eac8ad38f734774e595402520 100644
--- a/build/android/pylib/device/device_utils.py
+++ b/build/android/pylib/device/device_utils.py
@@ -11,6 +11,7 @@ Eventually, this will be based on adb_wrapper.
 import multiprocessing
 import os
 import pipes
+import re
 import sys
 import tempfile
 import time
@@ -86,6 +87,7 @@ class DeviceUtils(object):
     self._commands_installed = False
     self._default_timeout = default_timeout
     self._default_retries = default_retries
+    self._cache = {}
     assert(hasattr(self, decorators.DEFAULT_TIMEOUT_ATTR))
     assert(hasattr(self, decorators.DEFAULT_RETRIES_ATTR))
 
@@ -144,8 +146,8 @@ class DeviceUtils(object):
       raise device_errors.CommandFailedError(
           'Could not enable root.', device=str(self))
 
-  @decorators.WithTimeoutAndRetriesFromInstance()
-  def GetExternalStoragePath(self, timeout=None, retries=None):
+  def GetExternalStoragePath(self, timeout=_DEFAULT_TIMEOUT,

[jbudorick, 2014/10/14 16:55:19]

I'm not crazy about moving the timeout/retry boundary way down to the
implementation of AdbWrapper.Shell, which is what this appears to do. I'd like
to stick with handling them on the DeviceUtils boundary.

+                             retries=_DEFAULT_RETRIES):
     """Get the device's path to its SD card.
 
     Args:
@@ -160,14 +162,16 @@ class DeviceUtils(object):
       CommandTimeoutError on timeout.
       DeviceUnreachableError on missing device.
     """
-    return self._GetExternalStoragePathImpl()
+    if 'external_storage' in self._cache:
+      return self._cache['external_storage']
 
-  def _GetExternalStoragePathImpl(self):
-    try:
-      return self.old_interface.GetExternalStorage()
-    except AssertionError as e:
-      raise device_errors.CommandFailedError(
-          str(e), device=str(self)), None, sys.exc_info()[2]
+    value = self._NewRunShellImpl('echo $EXTERNAL_STORAGE', timeout=timeout,
+                                  retries=retries).rstrip()
+    if not value:

[jbudorick, 2014/10/14 16:55:19]

I'm not sure that this _has_ to be an error (although there may be enough
clients depending on it existing that it should be).

[perezju, 2014/10/15 09:22:54]

This is what the current implementation does, so not sure if clients are
depending on it.

+      raise device_errors.CommandFailedError('$EXTERNAL_STORAGE is not set',
+                                             str(self))
+    self._cache['external_storage'] = value

[jbudorick, 2014/10/14 16:55:19]

I like the idea of caching things like this and certain system properties -- we
do both of these already in AndroidCommands -- but let's talk about the
implementation.

[perezju, 2014/10/15 09:22:54]

Acknowledged.

+    return value
 
   @decorators.WithTimeoutAndRetriesFromInstance()
   def WaitUntilFullyBooted(self, wifi=False, timeout=None, retries=None):
@@ -326,6 +330,51 @@ class DeviceUtils(object):
       output = self.old_interface.RunShellCommand(cmd, timeout_time=timeout)
     return output
 
+  def _NewRunShellImpl(self, cmd, cwd=None, env=None, as_root=False,

[jbudorick, 2014/10/14 16:55:19]

I'm not sure about eliminating check_return here. I think the goal is to
eventually switch to default True, but I don't think we want to get rid of it.

[perezju, 2014/10/15 09:22:54]

I would argue that we shouldn't make it easy for clients to ignore errors. If a
non-zero exit code is to be expected, they should just catch the exception and
read the exit code from it. (And we should  make sure that the exception allows
to easily recover the exit code.) Thoughts?

+                       timeout=_DEFAULT_TIMEOUT, retries=_DEFAULT_RETRIES):
+    """Proposed new interface to run ADB shell commands.
+
+    When the command to run |cmd| is given as a string, it will be interpreted
+    and run by the shell on the device.
+
+    Alternatively, one can supply |cmd| as a sequence containing the name of
+    the command to run followed by its arguments. In this case, arguments are
+    passed to the command exactly as given, without any further processing by
+    the shell. This allows to easily pass arguments containing spaces or
+    special characters without having to worry about getting quoting right.
+
+    Args:
+      cmd: A string with the full command to run on the device, or a sequence
+        containing the command and its arguments.
+      cwd: The device directory in which the command should be run.
+      env: The environment variables with which the command should be run.
+      as_root: A boolean indicating whether the shell command should be run
+        with root privileges.
+      timeout: timeout in seconds
+      retries: number of retries
+
+    Returns:
+      The output of the command as a single string.
+
+    Raises:
+      CommandFailedError if the exit status of the command run is non-zero.
+      CommandTimeoutError on timeout.
+    """
+    def env_quote(key, value):
+      if not re.match('^[a-zA-Z_][a-zA-Z0-9_]*$', key):

[jbudorick, 2014/10/14 16:55:19]

Compile the regex as a constant and then use that to do the matching.

[perezju, 2014/10/15 09:22:54]

Acknowledged.

+        raise KeyError('Invalid shell variable name %r' % key)
+      return '%s=%s' % (key, pipes.quote(value))
+
+    if not isinstance(cmd, basestring):
+      cmd = ' '.join(pipes.quote(s) for s in cmd)
+    if as_root and not self._HasRootImpl():
+      cmd = 'su -c %s' % cmd
+    if env is not None:
+      cmd = '%s %s' % (' '.join(env_quote(*kv) for kv in env.iteritems()), cmd)

[jbudorick, 2014/10/14 16:55:19]

This seems a little more readable to me:

  env_quote(k, v) for k, v in env.iteritems()

[perezju, 2014/10/15 09:22:54]

Acknowledged.

+    if cwd is not None:
+      cmd = 'cd %s && %s' % (pipes.quote(cwd), cmd)
+    return self.adb.Shell(cmd, expect_rc=0, timeout=timeout, retries=retries)
+
   @decorators.WithTimeoutAndRetriesFromInstance()
   def KillAll(self, process_name, signum=9, as_root=False, blocking=False,
               timeout=None, retries=None):
@@ -622,7 +671,7 @@ class DeviceUtils(object):
       zip_proc.start()
       zip_proc.join()
 
-      zip_on_device = '%s/tmp.zip' % self._GetExternalStoragePathImpl()
+      zip_on_device = '%s/tmp.zip' % self.GetExternalStoragePath()
       try:
         self.adb.Push(zip_file.name, zip_on_device)
         self._RunShellCommandImpl(