Added support for migrating an old connections file.

Details:

* In _load_connections_file(), added support for migrating an old default
  connections file to the new name: If pywbemcli is invoked with the default
  connections file and it does not exist, but the old default connections
  file exists, it is renamed to the new default name and a message is
  issued about this.

* This required also performing this migration in the file_exists()
  method, which now calls _load_connections_file().

* Improved the message reporting connections file not found.

Signed-off-by: Andreas Maier <andreas.r.maier@gmx.de>

docs/changes.rst

@@ -87,6 +87,7 @@ Released: not yet
 * Renamed the default connections file in the user's home directory from
   `pywbemcli_connection_definitions.yaml` to `.pywbemcli_connections.yaml`,
   because it is really an internal file not meant for being edited.
+  An existing file with the old name is migrated automatically.
   (See issue #716)
 
 **Known issues:**

pywbemtools/pywbemcli/_connection_repository.py

@@ -39,18 +39,30 @@
 # with the use of the base file name in several other .rst and .py files.
 
 # Base file name of the connections file
+# The B08_* file name was used before pywbemcli 0.8.
 CONNECTIONS_FILENAME = '.pywbemcli_connections.yaml'
+B08_CONNECTIONS_FILENAME = 'pywbemcli_connection_definitions.yaml'
 
 # Path name of default connections file directory.
 DEFAULT_CONNECTIONS_DIR = os.path.expanduser("~")
 
 # Path name of default connections file
+# The B08_* path name was used before pywbemcli 0.8.
 DEFAULT_CONNECTIONS_FILE = os.path.join(DEFAULT_CONNECTIONS_DIR,
                                         CONNECTIONS_FILENAME)
+B08_DEFAULT_CONNECTIONS_FILE = os.path.join(DEFAULT_CONNECTIONS_DIR,
+                                            B08_CONNECTIONS_FILENAME)
 
 BAK_FILE_SUFFIX = 'bak'
 
 
+class ConnectionsFileNotFoundError(Exception):
+    """
+    Exception indicating that the connections file was not found.
+    """
+    pass
+
+
 class ConnectionRepository(object):
     # pylint: disable=useless-object-inheritance
     """
@@ -125,22 +137,29 @@ def default_connection_name(self):
 
     def file_exists(self):
         """
-        Test if the connection file exists
+        Test if the connection file exists.
+
+        An old connections file is migrated, if needed.
+        The connections file is loaded as part of the test.
 
         Returns:
             (:class:`py:bool`) True if the connections_file exists and False if
             it does not exist
         """
-        return os.path.isfile(self.connections_file)
+        try:
+            self._load_connections_file()
+            return True
+        except ConnectionsFileNotFoundError:
+            return False
 
     def __str__(self):
         """
         Return  a string containing connections file name and count of items in
         connections file
         """
         if self.file_exists():
+            # Has loaded the file
             status = 'exists'
-            self._load_connections_file()
             length = len(self)
         else:
             status = "does not exist"
@@ -210,17 +229,32 @@ def iterkeys(self):
 
     def _load_connections_file(self):
         """
-        If there is a file, read it in and install into the dictionary.
-        This file is read only once.
+        If the connections file exists, read it in and install into the
+        dictionary.
 
-        Raises:
-          IOError: repository does not exist
+        An old connections file is migrated, if needed.
+        Repeated calls to this method will load the file only once.
 
-          ValueError: Error in reading repository
+        Raises:
+          ConnectionsFileNotFoundError: Connections file not found
+          IOError: Cannot rename old connections file
+          ValueError,KeyError,TypeError: Error in connections file
         """
         if self._loaded:
             return
 
+        # Migrate an old connections file
+        if self._connections_file == DEFAULT_CONNECTIONS_FILE and \
+                not os.path.isfile(self._connections_file) and \
+                os.path.isfile(B08_DEFAULT_CONNECTIONS_FILE):
+
+            # May raise IOError:
+            os.rename(B08_DEFAULT_CONNECTIONS_FILE, DEFAULT_CONNECTIONS_FILE)
+
+            click.echo("Migrated old connections file {!r} to {!r}".
+                       format(B08_DEFAULT_CONNECTIONS_FILE,
+                              DEFAULT_CONNECTIONS_FILE))
+
         if os.path.isfile(self._connections_file):
             with self._open_file(self._connections_file, 'r') as _fp:
                 try:
@@ -252,11 +286,10 @@ def _load_connections_file(self):
                     raise ValueError("Invalid YAML in connections file {0}. "
                                      "Exception {1}".format
                                      (self._connections_file, ve))
-        # Apply IO error for non-existent file
-        # TODO. IOError can also mean disk full in general
         else:
-            raise IOError("Connections file {} does not exist.".
-                          format(self.connections_file))
+            raise ConnectionsFileNotFoundError(
+                "Connections file does not exist: {0}".
+                format(self.connections_file))
 
     def add(self, name, svr_definition):
         """
@@ -440,6 +473,6 @@ def get_default_connection_name(self):
 
         """
         if self.file_exists():
-            self._load_connections_file()
+            # Has loaded the file
             return self.default_connection_name
         return None

pywbemtools/pywbemcli/pywbemcli.py

@@ -78,7 +78,7 @@ def validate_connections_file(connections_repo):
     Abort click if file does not exist
     """
     if not connections_repo.file_exists():
-        click.echo('Connections file: "{}" does not exist.'.format(
+        click.echo('Connections file does not exist: {}'.format(
             connections_repo.connections_file), err=True)
         raise click.Abort()
 

tests/unit/test_general_options.py

@@ -474,7 +474,7 @@ class       Command group for CIM classes.
                   './filenotfound.yaml'],
       'cmdgrp': 'connection',
       'args': ['show']},
-     {'stderr': ['Connections file: "./filenotfound.yaml" does not exist.',
+     {'stderr': ['Connections file does not exist: ./filenotfound.yaml',
                  'Aborted!'],
       'rc': 1,
       'test': 'innows'},
@@ -485,7 +485,7 @@ class       Command group for CIM classes.
                   './filenotfound.yaml'],
       'cmdgrp': 'connection',
       'args': ['show']},
-     {'stderr': ['Connections file: "./filenotfound.yaml" does not exist.',
+     {'stderr': ['Connections file does not exist: ./filenotfound.yaml',
                  'Aborted!'],
       'rc': 1,
       'test': 'innows'},