avocado/core/settings.py: allow any settings to use the home dir notation

It's common to use the tilde notation (`~/foo`) to refer to locations
inside the user directory.  Let's introduce a new settings key type,
called `path`, that will automatically expand the tilde notation
if one is found.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/core/settings.py

@@ -107,6 +107,8 @@ def convert_value_type(value, value_type):
             value_type = float
         elif value_type == 'list':
             value_type = list
+        elif value_type == 'path':
+            value_type = os.path.expanduser
 
     if value_type is None:
         value_type = str
@@ -115,6 +117,8 @@ def convert_value_type(value, value_type):
     if len(sval) == 0:
         if value_type == str:
             return ""
+        elif value_type == os.path.expanduser:
+            return ""
         elif value_type == bool:
             return False
         elif value_type == int:
@@ -225,16 +229,24 @@ class Settings(object):
         Get value from key in a given config file section.
 
         :param section: Config file section.
+        :type section: str
         :param key: Config file key, relative to section.
+        :type key: str
         :param key_type: Type of key.
-                It can be either of: str, int, float, bool, list
+        :type key_type: either string based names representing types,
+                        including `str`, `int`, `float`, `bool`,
+                        `list` and `path`, or the types themselves
+                        limited to :class:`str`, :class:`int`,
+                        :class:`float`, :class:`bool` and
+                        :class:`list`.
         :param default: Default value for the key, if none found.
         :param allow_blank: Whether an empty value for the key is allowed.
 
         :returns: value, if one available in the config.
                 default value, if one provided.
 
-        :raises: SettingsError, in case no default was provided.
+        :raises: SettingsError, in case key is not set and no default
+                 was provided.
         """
         try:
             val = self.config.get(section, key)

selftests/unit/test_settings.py

@@ -16,6 +16,8 @@ float_key = 1.25
 bool_key = True
 list_key = ['I', 'love', 'settings']
 empty_key =
+path = ~/path/at/home
+home_path = ~
 """
 
 
@@ -41,6 +43,21 @@ class SettingsTest(unittest.TestCase):
     def testBoolConversion(self):
         self.assertTrue(self.settings.get_value('foo', 'bool_key', bool))
 
+    def testPathHomeDir(self):
+        raw_from_settings = '~/path/at/home'
+        path_from_settings = self.settings.get_value('foo', 'path', 'path')
+        home_str_from_settings = self.settings.get_value('foo', 'home_path', str)
+        self.assertEqual(path_from_settings[-13:],
+                         raw_from_settings[-13:])
+        self.assertGreaterEqual(len(path_from_settings),
+                                len(raw_from_settings))
+        self.assertEqual(os.path.expanduser(home_str_from_settings),
+                         self.settings.get_value('foo', 'home_path', 'path'))
+
+    def testPathOnStrKey(self):
+        self.assertEqual(self.settings.get_value('foo', 'path', str),
+                         '~/path/at/home')
+
     def testListConversion(self):
         self.assertEqual(self.settings.get_value('foo', 'list_key', list),
                          ['I', 'love', 'settings'])