target: resolve default paths eariler during the connection

Default paths for working_directory and exectuables_directory used to be
resolved at the end of the connect (because for Linux targets, the
default changes depending on the connection). This is now offloaded to a
separate internal method that is invoked earlier during connect() (after
the connection is established but before other connection actions are
resolved, as some of those actions rely on the directories being set).

devlib/target.py

@@ -176,6 +176,7 @@ class Target(object):
         self.platform.init_target_connection(self)
         tid = id(threading.current_thread())
         self._connections[tid] = self.get_connection(timeout=timeout)
+        self._resolve_paths()
         self.busybox = self.get_installed('busybox')
         self.platform.update_from_target(self)
         self._update_modules('connected')
@@ -437,6 +438,9 @@ class Target(object):
         else:
             self.logger.debug('Module {} is already installed.'.format(mod.name))
 
+    def _resolve_paths(self):
+        raise NotImplementedError()
+
 
 class LinuxTarget(Target):
 
@@ -473,13 +477,6 @@ class LinuxTarget(Target):
 
     def connect(self, timeout=None):
         super(LinuxTarget, self).connect(timeout=timeout)
-        if self.working_directory is None:
-            if self.connected_as_root:
-                self.working_directory = '/root/devlib-target'
-            else:
-                self.working_directory = '/home/{}/devlib-target'.format(self.user)
-        if self.executables_directory is None:
-            self.executables_directory = self.path.join(self.working_directory, 'bin')
 
     def kick_off(self, command, as_root=False):
         command = 'sh -c "{}" 1>/dev/null 2>/dev/null &'.format(escape_double_quotes(command))
@@ -547,6 +544,15 @@ class LinuxTarget(Target):
             message = e.message.split('OUTPUT:', 1)[1].strip()  # pylint: disable=no-member
             self.logger.debug('Could not take screenshot: {}'.format(message))
 
+    def _resolve_paths(self):
+        if self.working_directory is None:
+            if self.connected_as_root:
+                self.working_directory = '/root/devlib-target'
+            else:
+                self.working_directory = '/home/{}/devlib-target'.format(self.user)
+        if self.executables_directory is None:
+            self.executables_directory = self.path.join(self.working_directory, 'bin')
+
 
 class AndroidTarget(Target):
 
@@ -585,10 +591,6 @@ class AndroidTarget(Target):
             return (0, 0)
 
 
-    def __init__(self, *args, **kwargs):
-        super(AndroidTarget, self).__init__(*args, **kwargs)
-        self._file_transfer_cache = None
-
     def reset(self, fastboot=False):  # pylint: disable=arguments-differ
         try:
             self.execute('reboot {}'.format(fastboot and 'fastboot' or ''),
@@ -608,11 +610,6 @@ class AndroidTarget(Target):
             # always disconnect first.
             adb_disconnect(device)
         super(AndroidTarget, self).connect(timeout=timeout)
-        if self.working_directory is None:
-            self.working_directory = '/data/local/tmp/devlib-target'
-        self._file_transfer_cache = self.path.join(self.working_directory, '.file-cache')
-        if self.executables_directory is None:
-            self.executables_directory = self.path.join(self.working_directory, 'bin')
 
         if check_boot_completed:
             boot_completed = boolean(self.getprop('sys.boot_completed'))
@@ -793,6 +790,13 @@ class AndroidTarget(Target):
         if not self.is_screen_on():
             self.execute('input keyevent 26')
 
+    def _resolve_paths(self):
+        if self.working_directory is None:
+            self.working_directory = '/data/local/tmp/devlib-target'
+        self._file_transfer_cache = self.path.join(self.working_directory, '.file-cache')
+        if self.executables_directory is None:
+            self.executables_directory = self.path.join(self.working_directory, 'bin')
+
     def _ensure_executables_directory_is_writable(self):
         matched = []
         for entry in self.list_file_systems():
@@ -954,12 +958,11 @@ class LocalLinuxTarget(LinuxTarget):
 
     conn_cls = LocalConnection
 
-    def connect(self, timeout=None):
+    def _resolve_paths(self):
         if self.working_directory is None:
             self.working_directory = '/tmp'
         if self.executables_directory is None:
             self.executables_directory = '/tmp'
-        super(LocalLinuxTarget, self).connect(timeout)
 
 
 def _get_model_name(section):