CLI: Make loading of config lazy

The `VerdiContext` class, which provides the custom context of the
`verdi` commands, loads the configuration. This has a non-negligible
cost and so slows down the responsiveness of the CLI. This is especially
noticeable during tab-completion.

The `obj` custom object of the `VerdiContext` is replaced with a
subclass of `AttributeDict` that lazily populates the `config` key when
it is called with the loaded `Config` class. In addition, the defaults
of some options of the `verdi setup` command, which load a value from
the config and so require the config, are turned into partials such that
they also are lazily evaluated. These changes should give a reduction in
load time of `verdi` of the order of ~50 ms.

A test of `verdi setup` had to be updated to explicitly provide a value
for the email. This is because now the default is evaluated lazily, i.e.
when the command is actually called in the test. At this point, there is
no value for this config option and so the default is empty. Before, the
default would be evaluated as soon as `aiida.cmdline.commands.cmd_setup`
was imported, at which point an existing config would still contain
these values, binding them to the default, even if the config would be
reset afterwards before the test.

Author: danielhollas

aiida/cmdline/groups/verdi.py

@@ -34,19 +34,40 @@
 )
 
 
+class LazyConfigAttributeDict(AttributeDict):
+    """We want to avoid needlesly loading user config on every verdi invocation"""
+
+    _LAZY_KEY = 'config'
+
+    def __init__(self, ctx, dictionary=None):
+        super().__init__(dictionary)
+        # We need click context so we can stop in case we fail to parse the config
+        self.ctx = ctx
+
+    def __getattr__(self, attr):
+        """Override of AttributeDict.__getattr__ for lazy loading the config key.
+
+        Stops if config file cannot be parsed.
+        :raises AttributeError: if the attribute does not correspond to an existing key.
+        """
+        if attr != self._LAZY_KEY:
+            return super().__getattr__(attr)
+
+        if self._LAZY_KEY not in self:
+            try:
+                self[self._LAZY_KEY] = get_config(create=True)
+            except ConfigurationError as exception:
+                self.ctx.fail(str(exception))
+        return self[self._LAZY_KEY]
+
+
 class VerdiContext(click.Context):
     """Custom context implementation that defines the ``obj`` user object and adds the ``Config`` instance."""
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
-
         if self.obj is None:
-            self.obj = AttributeDict()
-
-        try:
-            self.obj.config = get_config(create=True)
-        except ConfigurationError as exception:
-            self.fail(str(exception))
+            self.obj = LazyConfigAttributeDict(self)
 
 
 class VerdiCommandGroup(click.Group):

aiida/cmdline/params/options/commands/setup.py

@@ -176,28 +176,28 @@ def get_quicksetup_password(ctx, param, value):  # pylint: disable=unused-argume
 
 SETUP_USER_EMAIL = options.USER_EMAIL.clone(
     prompt='Email Address (for sharing data)',
-    default=get_config_option('autofill.user.email'),
+    default=functools.partial(get_config_option, 'autofill.user.email'),
     required=True,
     cls=options.interactive.InteractiveOption
 )
 
 SETUP_USER_FIRST_NAME = options.USER_FIRST_NAME.clone(
     prompt='First name',
-    default=get_config_option('autofill.user.first_name'),
+    default=functools.partial(get_config_option, 'autofill.user.first_name'),
     required=True,
     cls=options.interactive.InteractiveOption
 )
 
 SETUP_USER_LAST_NAME = options.USER_LAST_NAME.clone(
     prompt='Last name',
-    default=get_config_option('autofill.user.last_name'),
+    default=functools.partial(get_config_option, 'autofill.user.last_name'),
     required=True,
     cls=options.interactive.InteractiveOption
 )
 
 SETUP_USER_INSTITUTION = options.USER_INSTITUTION.clone(
     prompt='Institution',
-    default=get_config_option('autofill.user.institution'),
+    default=functools.partial(get_config_option, 'autofill.user.institution'),
     required=True,
     cls=options.interactive.InteractiveOption
 )

tests/cmdline/commands/test_setup.py

@@ -205,11 +205,12 @@ def test_setup_profile_uuid(self):
         postgres.create_db(db_user, db_name)
 
         profile_name = 'profile-copy'
+        user_email = 'some@email.com'
         profile_uuid = str(uuid.uuid4)
         options = [
             '--non-interactive', '--profile', profile_name, '--profile-uuid', profile_uuid, '--db-backend',
             self.storage_backend_name, '--db-name', db_name, '--db-username', db_user, '--db-password', db_pass,
-            '--db-port', self.pg_test.dsn['port']
+            '--db-port', self.pg_test.dsn['port'], '--email', user_email
         ]
 
         self.cli_runner(cmd_setup.setup, options, use_subprocess=False)