Better error handling

diff --git a/shbackup b/shbackup
index db2c66125b3f09514f21f809dbaf842e86270ddb..cbd5396cc897636c93a272c4df36caae195c4818 100755 (executable)
--- a/shbackup
+++ b/shbackup
@@ -52,9 +52,11 @@ class Backup:
 class Config:
     """Encapsules the configuration for the backup program."""
 
-    class ReadException(Exception):
+    class ReadError(RuntimeError):
         """An exception raised when reading configurations."""
-        pass
+        def __init__(self, value):
+            self.value = value
+            self.message = value
 
     class FileSet:
         """A fileset has a name and a list of directories."""
@@ -92,20 +94,22 @@ class Config:
         """Read configuration from file"""
 
         if not os.path.isfile(filename):
-            raise Config.ReadException("No file '" + filename + "'.")
+            raise Config.ReadError("Cannot read config file '" + filename + "'.")
 
         config = configparser.RawConfigParser()
         config.read(filename)
 
         for reqsec in ["destination"]:
             if not config.has_section(reqsec):
-                raise Config.ReadException("Section '" + reqsec + "' is missing.")
+                raise Config.ReadError("Section '" + reqsec + "' is missing.")
 
         self.directory = config.get("destination", "directory")
+        if not os.path.isdir(self.directory):
+            raise Config.ReadError("Directory '{0}' does not exist.".format(self.directory))
 
         self.format = config.get("destination", "format")
         if not self.format in Config.formats:
-            raise Config.ReadException("Invalid 'format' given.")
+            raise Config.ReadError("Invalid 'format' given.")
 
 
         if config.has_section("history"):
@@ -113,24 +117,27 @@ class Config:
                 if opt.startswith("keep"):
                     epoch = opt[4:]
                     if not epoch in RealEpoch.keys():
-                        raise Config.ReadException("Invalid option 'keep" + epoch + "'.")
-                    self.epochkeeps[epoch] = int(config.getint("history", opt))
+                        raise Config.ReadError("Invalid option 'keep" + epoch + "'.")
+                    try:
+                        self.epochkeeps[epoch] = int(config.getint("history", opt))
+                    except ValueError:
+                        raise Config.ReadError("Invalid integer given for '" + opt + "'.")
                 elif opt.startswith("mode"):
                     epoch = opt[4:]
                     if not epoch in RealEpoch.keys():
-                        raise Config.ReadException("Invalid option 'mode" + epoch + "'.")
+                        raise Config.ReadError("Invalid option 'mode" + epoch + "'.")
                     self.epochmodes[epoch] = config.get("history", opt)
                     if not self.epochmodes[epoch] in Mode:
-                        raise Config.ReadException("Invalid mode given.")
+                        raise Config.ReadError("Invalid mode given.")
                 else:
-                    raise Config.ReadException("Invalid option '" + opt + "'.")
+                    raise Config.ReadError("Invalid option '" + opt + "'.")
 
         if config.has_section("input"):
             for opt in config.options("input"):
                 if opt.startswith("exclude"):
                     self.exclpatterns += [ config.get("input", opt) ]
                 else:
-                    raise Config.ReadException("Invalid option '" + opt + "'.")
+                    raise Config.ReadError("Invalid option '" + opt + "'.")
 
         for sec in config.sections():
             if sec in ["destination", "history", "input"]:
@@ -141,12 +148,12 @@ class Config:
 
                 for opt in config.options(sec):
                     if not opt.startswith("dir"):
-                        raise Config.ReadException("Unknown option '" + opt + "'.")
+                        raise Config.ReadError("Unknown option '" + opt + "'.")
                     else:
                         dirs += [config.get(sec, opt)]
                 self.sets += [Config.FileSet(name, dirs)]
             else:
-                raise Config.ReadException("Unknown section '" + sec + "'.")
+                raise Config.ReadError("Unknown section '" + sec + "'.")
 
         # Compute checksum of config file
         m = hashlib.sha1()
@@ -428,11 +435,8 @@ if __name__ == "__main__":
         if cmd == "prune":
             man.prune()
 
-    except Config.ReadException as e:
-        print("Error reading config file: ", end="")
-        for a in e.args:
-            print(a, end=" ")
-        print()
+    except (Config.ReadError, configparser.DuplicateOptionError) as e:
+        print("Error reading config file: " + e.message)