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Make Dispatcher a singleton after first instantiation

This allows plugins to re-instantiate the Dispatcher
(or, now, use the instance cached in `current_dispatcher`)
without knowing what plugins have been loaded by dotbot.

This fixes plugins that want to dispatch to other plugins.

Fixes #339
This commit is contained in:
Kurt McKee 2023-09-10 10:07:49 -05:00
parent 840cd164d2
commit 25497721a3
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GPG Key ID: 64713C0B5BA8E1C2
3 changed files with 47 additions and 0 deletions

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@ -5,8 +5,23 @@ from .context import Context
from .messenger import Messenger
from .plugin import Plugin
current_dispatcher = None
class Dispatcher:
def __new__(cls, *args, **kwargs):
# After dotbot instantiates this class, the instance will be cached.
# Subsequent instantiations (say, by plugins) will return the same instance.
# This is needed because plugins don't have access to the entire configuration
# (for example, they won't know which plugins have been loaded).
# This ensures a consistent configuration is used.
global current_dispatcher
if current_dispatcher is None:
instance = object.__new__(cls)
instance.is_initialized = False
current_dispatcher = instance
return current_dispatcher
def __init__(
@ -16,6 +31,9 @@ class Dispatcher:
if self.is_initialized:
self.is_initialized = True
self._log = Messenger()
self._setup_context(base_directory, options)
plugins = plugins or []

View File

@ -12,6 +12,7 @@ import pytest
import yaml
import dotbot.cli
import dotbot.dispatcher
def get_long_path(path):
@ -312,3 +313,9 @@ def run_dotbot(dotfiles):
yield runner
def reset_current_dispatcher():
dotbot.dispatcher.current_dispatcher = None

tests/test_dispatcher.py Normal file
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@ -0,0 +1,22 @@
import dotbot.dispatcher
def test_dispatcher_instantiation(home, dotfiles, run_dotbot):
"""Verify that the dispatcher caches itself as a singleton."""
assert dotbot.dispatcher.current_dispatcher is None
# Verify the dispatcher has been cached.
assert dotbot.dispatcher.current_dispatcher is not None
existing_id = id(dotbot.dispatcher.current_dispatcher)
new_instance = dotbot.dispatcher.Dispatcher("bogus")
# Verify the new and existing instances are the same.
assert existing_id == id(new_instance)
# Verify the singleton was not overridden.
assert existing_id == id(dotbot.dispatcher.current_dispatcher)