Add more diagnostic tracing when a JSON call doesn't return.

chrome/test/pyautolib/pyauto.py

Index: chrome/test/pyautolib/pyauto.py
===================================================================
--- chrome/test/pyautolib/pyauto.py	(revision 131795)
+++ chrome/test/pyautolib/pyauto.py	(working copy)
@@ -935,7 +935,28 @@
       return self._ui_test.ExecuteJavascriptInRenderView(script,
                                                          self.view,
                                                          self.frame_xpath)
+  def _GetResultFromJSONRequestDiagnostics(self, cmd_dict, windex=0,
+                                           timeout=-1):
+    """Same as _GetResultFromJSONRequest without throwing a timeout exception.
 
+    This method is used to diagnose if a command returns without causing a
+    timout exception to be thrown.  This should be used for debugging purposes
+    only.
+
+    Returns:
+      True if the request returned; False if it timed out.
+    """
+    if timeout == -1:  # Default
+      timeout = self.action_max_timeout_ms()
+    if windex is None:  # Do not target any window
+      windex = -1
+    result = self._SendJSONRequest(windex, json.dumps(cmd_dict), timeout)
+    if not result:
+      # The diagnostic command did not complete, Chrome is probably in a bad
+      # state
+      return False
+    return True
+
   def _GetResultFromJSONRequest(self, cmd_dict, windex=0, timeout=-1):
     """Issue call over the JSON automation channel and fetch output.
 
@@ -971,14 +992,29 @@
       additional_info = 'No information available.'
       # Windows does not support os.kill until Python 2.7.
       if not self.IsWin() and _BROWSER_PID:
-        additional_info = ('The browser process ID %d still exists. '
-                           'It is possible that it is hung.' % _BROWSER_PID)
+        browser_pid_exists = True
+        # Does the browser PID exist?
         try:
           # Does not actually kill the process
           os.kill(int(_BROWSER_PID), 0)
         except OSError:
-          additional_info = ('The browser process ID %d no longer exists.' %
-                             _BROWSER_PID)
+          browser_pid_exists = False
+        if browser_pid_exists:
+          info = GetBrowserInfo(self, performing_diagnostics=True)
+          if info:
+            # Browser info, worked, that means this hook had a problem
+            additional_info = ('The browser process ID %d still exists. '
+                               'PyAuto was able to get obtain browser info. It '
+                               'is possible this hook is broken.'

[Nirnimesh, 2012/04/12 23:04:07]

add a name to the hook: cmd_dict.get('command')

+                               % _BROWSER_PID)
+          else:
+            additional_info = ('The browser process ID %d still exists. '
+                               'PyAuto was not able to obtain browser info. '
+                               'It is possible the browser is hung.'
+                               % _BROWSER_PID)
+        else:
+          additional_info = ('The browser process ID %d no longer exists. '
+                             'Perhaps the browser crashed.' % _BROWSER_PID)
       elif not _BROWSER_PID:
         additional_info = ('The browser PID was not obtained. Does this test '
                            'have a unique startup configuration?')
@@ -1594,7 +1630,7 @@
       raise JSONInterfaceError('Invalid action %s' % action)
     self._GetResultFromJSONRequest(cmd_dict, windex=windex)
 
-  def GetBrowserInfo(self):
+  def GetBrowserInfo(self, performing_diagnostics=False):

[Nirnimesh, 2012/04/12 23:04:07]

I don't like that you're picking between the 2 methods, based on this flag. I
think you should leave this as-is, and..
1. Make your new diagnostic function be a wrapper around
_GetResultFromJSONRequest() and force it to call with cmd_dict {'command':
'GetBrowserInfo', 'windex': 0}

     """Return info about the browser.
 
     This includes things like the version number, the executable name,
@@ -1603,6 +1639,10 @@
 
     For notification pid info, see 'GetActiveNotifications'.
 
+    Args:
+      performing_diagnostics: This is only used when we are trying to debug why
+                              the previous hook failed to return.
+
     Returns:
       a dictionary
 
@@ -1681,6 +1721,10 @@
     cmd_dict = {  # Prepare command for the json interface
       'command': 'GetBrowserInfo',
     }
+    if performing_diagnostics:
+      self._GetResultFromJSONRequestDiagnostics(cmd_dict, windex=None)

[Nirnimesh, 2012/04/12 23:04:07]

return the output of this call

+      return
+
     return self._GetResultFromJSONRequest(cmd_dict, windex=None)
 
   def IsAura(self):