Introduce CustomConfig method that applies set of transforms

It is a bit cleaner than making chains of calls like
{{{
value = os.path.expanduser(value)
value = os.path.abspath(value)
}}}
since we do see all transformations to be applied in a single
iterable and have no repeated code like in the above example.

Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

offlineimap/CustomConfig.py

@@ -94,14 +94,17 @@ class CustomConfigParser(SafeConfigParser):
             return default
 
     def getmetadatadir(self):
-        metadatadir = os.path.expanduser(self.getdefault("general", "metadata", "~/.offlineimap"))
+        xforms = [os.path.expanduser]
+        d = self.getdefault("general", "metadata", "~/.offlineimap")
+        metadatadir = self.apply_xforms(d, xforms)
         if not os.path.exists(metadatadir):
             os.mkdir(metadatadir, 0o700)
         return metadatadir
 
     def getlocaleval(self):
+        xforms = [os.path.expanduser]
         if self.has_option("general", "pythonfile"):
-            path = os.path.expanduser(self.get("general", "pythonfile"))
+            path = self.apply_xforms(self.get("general", "pythonfile"), xforms)
         else:
             path = None
         return LocalEval(path)
@@ -132,6 +135,26 @@ class CustomConfigParser(SafeConfigParser):
             self.set(section, option, value)
 
 
+    def apply_xforms(self, string, transforms):
+        """
+        Applies set of transformations to a string.
+
+        Arguments:
+         - string: source string; if None, then no processing will
+           take place.
+         - transforms: iterable that returns transformation function
+           on each turn.
+
+        Returns transformed string.
+
+        """
+        if string == None:
+            return None
+        for f in transforms:
+            string = f(string)
+        return string
+
+
 
 def CustomConfigDefault():
     """
@@ -161,9 +184,10 @@ class ConfigHelperMixin:
     
     """
 
+
     def _confighelper_runner(self, option, default, defaultfunc, mainfunc, *args):
         """
-        Return configuration or default value for option
+        Returns configuration or default value for option
         that contains in section identified by getsection().
 
         Arguments:
@@ -213,27 +237,96 @@ class ConfigHelperMixin:
 
 
     def getconf(self, option, default = CustomConfigDefault):
+        """
+        Retrieves string from the configuration.
+
+        Arguments:
+         - option: option name whose value is to be retrieved;
+         - default: default return value if no such option
+           exists.
+
+        """
         return self._confighelper_runner(option, default,
                                          self.getconfig().getdefault,
                                          self.getconfig().get)
 
+
+    def getconf_xform(self, option, xforms, default = CustomConfigDefault):
+        """
+        Retrieves string from the configuration transforming the result.
+
+        Arguments:
+         - option: option name whose value is to be retrieved;
+         - xforms: iterable that returns transform functions
+           to be applied to the value of the option,
+           both retrieved and default one;
+         - default: default value for string if no such option
+           exists.
+
+        """
+        value = self.getconf(option, default)
+        return self.getconfig().apply_xforms(value, xforms)
+
+
     def getconfboolean(self, option, default = CustomConfigDefault):
+        """
+        Retrieves boolean value from the configuration.
+
+        Arguments:
+         - option: option name whose value is to be retrieved;
+         - default: default return value if no such option
+           exists.
+
+        """
         return self._confighelper_runner(option, default,
                                          self.getconfig().getdefaultboolean,
                                          self.getconfig().getboolean)
 
+
     def getconfint(self, option, default = CustomConfigDefault):
+        """
+        Retrieves integer value from the configuration.
+
+        Arguments:
+         - option: option name whose value is to be retrieved;
+         - default: default return value if no such option
+           exists.
+
+        """
         return self._confighelper_runner(option, default,
                                          self.getconfig().getdefaultint,
                                          self.getconfig().getint)
 
+
     def getconffloat(self, option, default = CustomConfigDefault):
+        """
+        Retrieves floating-point value from the configuration.
+
+        Arguments:
+         - option: option name whose value is to be retrieved;
+         - default: default return value if no such option
+           exists.
+
+        """
         return self._confighelper_runner(option, default,
                                          self.getconfig().getdefaultfloat,
                                          self.getconfig().getfloat)
 
+
     def getconflist(self, option, separator_re,
                     default = CustomConfigDefault):
+        """
+        Retrieves strings from the configuration and splits it
+        into the list of strings.
+
+        Arguments:
+         - option: option name whose value is to be retrieved;
+         - separator_re: regular expression for separator
+           to be used for split operation;
+         - default: default return value if no such option
+           exists.
+
+        """
         return self._confighelper_runner(option, default,
                                          self.getconfig().getdefaultlist,
                                          self.getconfig().getlist, separator_re)

offlineimap/repository/IMAP.py

@@ -201,11 +201,11 @@ class IMAPRepository(BaseRepository):
 
     def getsslcacertfile(self):
         """Return the absolute path of the CA certfile to use, if any"""
-        cacertfile = self.getconf('sslcacertfile', get_os_sslcertfile())
+        xforms = [os.path.expanduser, os.path.abspath]
+        cacertfile = self.getconf_xform('sslcacertfile', xforms,
+          get_os_sslcertfile())
         if cacertfile is None:
             return None
-        cacertfile = os.path.expanduser(cacertfile)
-        cacertfile = os.path.abspath(cacertfile)
         if not os.path.isfile(cacertfile):
             raise SyntaxWarning("CA certfile for repository '%s' could "
                                 "not be found. No such file: '%s'" \

offlineimap/repository/Maildir.py

@@ -61,7 +61,8 @@ class MaildirRepository(BaseRepository):
             os.utime(cur_dir, (cur_atime, os.path.getmtime(cur_dir)))
 
     def getlocalroot(self):
-        return os.path.expanduser(self.getconf('localfolders'))
+        xforms = [os.path.expanduser]
+        return self.getconf_xform('localfolders', xforms)
 
     def debug(self, msg):
         self.ui.debug('maildir', msg)