Lazily load storages

CHANGELOG.rst

@@ -15,6 +15,8 @@ Version 0.5.0
 *yet to be released*
 
 - Raise version of required requests-toolbelt to ``0.4.0``.
+- Command line should be a lot faster when no work is done, e.g. for help
+  output.
 
 Version 0.4.4
 =============

tests/cli/test_config.py

@@ -61,7 +61,8 @@ def test_storage_instance_from_config(monkeypatch):
         return 'OK'
 
     import vdirsyncer.storage
-    monkeypatch.setitem(vdirsyncer.cli.utils.storage_names, 'lol', lol)
+    monkeypatch.setitem(vdirsyncer.cli.utils.storage_names._storages,
+                        'lol', lol)
     config = {'type': 'lol', 'foo': 'bar', 'baz': 1}
     assert cli.utils.storage_instance_from_config(config) == 'OK'
 

tests/utils/test_main.py

@@ -11,10 +11,14 @@ import pytest
 
 import requests
 
-import vdirsyncer.doubleclick as doubleclick
+from vdirsyncer import doubleclick, utils
-import vdirsyncer.utils.http
+
-import vdirsyncer.utils.password
+# These modules might be uninitialized and unavailable if not explicitly
-import vdirsyncer.utils as utils
+# imported
+import vdirsyncer.utils.compat  # noqa
+import vdirsyncer.utils.http  # noqa
+import vdirsyncer.utils.password  # noqa
+
 
 from .. import blow_up
 

vdirsyncer/cli/utils.py

@@ -2,6 +2,7 @@
 
 import errno
 import hashlib
+import importlib
 import json
 import os
 import string
@@ -31,31 +32,30 @@ except ImportError:
     import queue
 
 
-def _generate_storage_dict():
+class _StorageIndex(object):
-    from ..storage.dav import CaldavStorage, CarddavStorage
+    def __init__(self):
-    from ..storage.filesystem import FilesystemStorage
+        self._storages = dict(
-    from ..storage.http import HttpStorage
+            caldav='vdirsyncer.storage.dav.CaldavStorage',
-    from ..storage.singlefile import SingleFileStorage
+            carddav='vdirsyncer.storage.dav.CarddavStorage',
-
+            filesystem='vdirsyncer.storage.filesystem.FilesystemStorage',
-    classes = (
+            http='vdirsyncer.storage.http.HttpStorage',
-        CaldavStorage,
+            singlefile='vdirsyncer.storage.singlefile.SingleFileStorage',
-        CarddavStorage,
-        FilesystemStorage,
-        HttpStorage,
-        SingleFileStorage
         )
 
-    rv = {}
+    def __getitem__(self, name):
-    for cls in classes:
+        item = self._storages[name]
-        key = cls.storage_name
+        if not isinstance(item, str):
-        assert key
+            return item
-        assert isinstance(key, str)
+
-        assert key not in rv
+        modname, clsname = item.rsplit('.', 1)
-        rv[key] = cls
+        mod = importlib.import_module(modname)
+        self._storages[name] = rv = getattr(mod, clsname)
+        assert rv.storage_name == name
         return rv
 
-storage_names = _generate_storage_dict()
+
-del _generate_storage_dict
+storage_names = _StorageIndex()
+del _StorageIndex
 
 
 cli_logger = log.get(__name__)
@@ -444,8 +444,9 @@ def save_status(base_path, pair, collection=None, data_type=None, data=None):
 def storage_class_from_config(config):
     config = dict(config)
     storage_name = config.pop('type')
-    cls = storage_names.get(storage_name, None)
+    try:
-    if cls is None:
+        cls = storage_names[storage_name]
+    except KeyError:
         raise CliError('Unknown storage type: {}'.format(storage_name))
     return cls, config
 

vdirsyncer/utils/__init__.py

@@ -4,7 +4,7 @@ import os
 import sys
 
 from .compat import iteritems
-from .. import exceptions, log
+from .. import exceptions
 
 
 _missing = object()