[Android] Upstreaming flag_changer.py

build/android/flag_changer.py

 # Copyright (c) 2012 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 traceback
+import warnings
+
 
 # Location where chrome reads command line flags from
-CHROME_COMMAND_FILE = '/data/local/tmp/chrome-command-line'
-
+CHROME_COMMAND_FILE = '/data/local/chrome-command-line'

[John Grabowski, 2012/06/26 07:26:30]

You changed the command line file from the default location without changing
code that finds this file.  Was that your intention?  Will things still work
with this change?

 
 class FlagChanger(object):
-  """Temporarily changes the flags Chrome runs with."""
+  """Changes the flags Chrome runs with.
+
+  There are two different use cases for this file:
+  * Flags are permanently set by calling Set().
+  * Flags can be temporarily set for a particular set of unit tests.  These
+    tests should call Restore() to revert the flags to their original state
+    once the tests have completed.
+  """
 
   def __init__(self, android_cmd):
     self._android_cmd = android_cmd
-    self._old_flags = None
 
-  def Set(self, flags, append=False):
-    """Sets the command line flags used when chrome is started.
+    # Save the original flags.
+    self._orig_line = self._android_cmd.GetFileContents(CHROME_COMMAND_FILE)
+    if self._orig_line:
+      self._orig_line = self._orig_line[0].strip()
+
+    # Parse out the flags into a list to facilitate adding and removing flags.
+    self._current_flags = self._TokenizeFlags(self._orig_line)
+
+  def Get(self):
+    """Returns list of current flags."""
+    return self._current_flags
+
+  def Set(self, flags):
+    """Replaces all flags on the current command line with the flags given.
 
     Args:
       flags: A list of flags to set, eg. ['--single-process'].
-      append: Whether to append to existing flags or overwrite them.
     """
     if flags:
       assert flags[0] != 'chrome'
 
-    if not self._old_flags:
-      self._old_flags = self._android_cmd.GetFileContents(CHROME_COMMAND_FILE)
-      if self._old_flags:
-        self._old_flags = self._old_flags[0].strip()
+    self._current_flags = flags
+    self._UpdateCommandLineFile()
 
-    if append and self._old_flags:
-      # Avoid appending flags that are already present.
-      new_flags = filter(lambda flag: self._old_flags.find(flag) == -1, flags)
-      self._android_cmd.SetFileContents(CHROME_COMMAND_FILE,
-                                        self._old_flags + ' ' +
-                                        ' '.join(new_flags))
-    else:
-      self._android_cmd.SetFileContents(CHROME_COMMAND_FILE,
-                                        'chrome ' + ' '.join(flags))
+  def AddFlags(self, flags):
+    """Appends flags to the command line if they aren't already there.
+
+    Args:
+      flags: A list of flags to add on, eg. ['--single-process'].
+    """
+    if flags:
+      assert flags[0] != 'chrome'
+
+    # Avoid appending flags that are already present.
+    for flag in flags:
+      if flag not in self._current_flags:
+        self._current_flags.append(flag)
+    self._UpdateCommandLineFile()
+
+  def RemoveFlags(self, flags):
+    """Removes flags from the command line, if they exist.
+
+    Args:
+      flags: A list of flags to remove, eg. ['--single-process'].  Note that we
+             expect a complete match when removing flags; if you want to remove
+             a switch with a value, you must use the exact string used to add
+             it in the first place.
+    """
+    if flags:
+      assert flags[0] != 'chrome'
+
+    for flag in flags:
+      if flag in self._current_flags:
+        self._current_flags.remove(flag)
+    self._UpdateCommandLineFile()
 
   def Restore(self):
     """Restores the flags to their original state."""
-    if self._old_flags == None:
-      return  # Set() was never called.
-    elif self._old_flags:
-      self._android_cmd.SetFileContents(CHROME_COMMAND_FILE, self._old_flags)
+    self._current_flags = self._TokenizeFlags(self._orig_line)
+    self._UpdateCommandLineFile()
+
+  def _UpdateCommandLineFile(self):
+    """Writes out the command line to the file, or removes it if empty."""
+    print "Current flags: ", self._current_flags
+
+    if self._current_flags:
+      self._android_cmd.SetFileContents(CHROME_COMMAND_FILE,
+                                        'chrome ' +
+                                        ' '.join(self._current_flags))
     else:
       self._android_cmd.RunShellCommand('rm ' + CHROME_COMMAND_FILE)
+
+  def _TokenizeFlags(self, line):
+    """Changes the string containing the command line into a list of flags.
+
+    Follows similar logic to CommandLine.java::tokenizeQuotedArguments:
+    * Flags are split using whitespace, unless the whitespace is within a
+      pair of quotation marks.
+    * Unlike the Java version, we keep the quotation marks around switch
+      values since we need them to re-create the file when new flags are
+      appended.
+
+    Args:
+      line: A string containing the entire command line.  The first token is
+            assumed to be the program name.
+    """
+    if not line:
+      return []
+
+    tokenized_flags = []
+    current_flag = ""
+    within_quotations = False
+
+    # Move through the string character by character and build up each flag
+    # along the way.
+    for c in line.strip():
+      if c is '"':
+        if len(current_flag) > 0 and current_flag[-1] == '\\':
+          # Last char was a backslash; pop it, and treat this " as a literal.
+          current_flag = current_flag[0:-1] + '"'
+        else:
+          within_quotations = not within_quotations
+          current_flag += c
+      elif not within_quotations and (c is ' ' or c is '\t'):
+        if current_flag is not "":
+          tokenized_flags.append(current_flag)
+          current_flag = ""
+      else:
+        current_flag += c
+
+    # Tack on the last flag.
+    if not current_flag:
+      if within_quotations:
+        warnings.warn("Unterminated quoted string: " + current_flag)
+    else:
+      tokenized_flags.append(current_flag)
+
+    # Return everything but the program name.
+    return tokenized_flags[1:]