Make Dispatcher have all plugins by default

This used to be the behavior, and then
b5499c7 changed this, breaking some
plugins (some of which subsequently implemented workarounds). This patch
restores the behavior, so that if a Dispatcher is constructed without
explicitly passing in plugins, it has access to all plugins.

This change seems safe, in that it's unlikely that any plugins were
relying on the behavior between b5499c7
and this patch, where a Dispatcher without an explicit plugin list
behaved as if there were no plugins---because such a Dispatcher is not
very useful!

dotbot/cli.py

@@ -7,7 +7,7 @@
 import dotbot
 
 from .config import ConfigReader, ReadingError
-from .dispatcher import Dispatcher, DispatchError
+from .dispatcher import Dispatcher, DispatchError, _all_plugins
 from .messenger import Level, Messenger
 from .plugins import Clean, Create, Link, Shell
 from .util import module
@@ -151,6 +151,7 @@ def main():
             # default to directory of config file
             base_directory = os.path.dirname(os.path.abspath(options.config_file))
         os.chdir(base_directory)
+        _all_plugins[:] = plugins  # for backwards compatibility, see dispatcher.py
         dispatcher = Dispatcher(
             base_directory,
             only=options.only,

dotbot/dispatcher.py

@@ -5,6 +5,14 @@
 from .messenger import Messenger
 from .plugin import Plugin
 
+# Before b5499c7dc5b300462f3ce1c2a3d9b7a76233b39b, Dispatcher auto-loaded all
+# plugins, but after that change, plugins are passed in explicitly (and loaded
+# in cli.py). There are some plugins that rely on the old Dispatcher behavior,
+# so this is a workaround for implementing similar functionality: when
+# Dispatcher is constructed without an explicit list of plugins, _all_plugins is
+# used instead.
+_all_plugins = []  # filled in by cli.py
+
 
 class Dispatcher:
     def __init__(
@@ -16,9 +24,12 @@ def __init__(
         options=Namespace(),
         plugins=None,
     ):
+        # if the caller wants no plugins, the caller needs to explicitly pass in
+        # plugins=[]
         self._log = Messenger()
         self._setup_context(base_directory, options, plugins)
-        plugins = plugins or []
+        if plugins is None:
+            plugins = _all_plugins
         self._plugins = [plugin(self._context) for plugin in plugins]
         self._only = only
         self._skip = skip

tests/dotbot_plugin_dispatcher_no_plugins.py

@@ -0,0 +1,18 @@
+# https://github.com/anishathalye/dotbot/issues/339, https://github.com/anishathalye/dotbot/pull/332
+# if plugins instantiate a Dispatcher without explicitly passing in plugins,
+# the Dispatcher should have access to all plugins (matching context.plugins())
+
+import dotbot
+from dotbot.dispatcher import Dispatcher
+
+
+class Dispatch(dotbot.Plugin):
+    def can_handle(self, directive):
+        return directive == "dispatch"
+
+    def handle(self, directive, data):
+        dispatcher = Dispatcher(
+            base_directory=self._context.base_directory(),
+            options=self._context.options(),
+        )
+        return dispatcher.dispatch(data)

tests/test_cli.py

@@ -199,3 +199,17 @@ def test_plugin_context_plugin(capfd, home, dotfiles, run_dotbot):
 
     stdout = capfd.readouterr().out.splitlines()
     assert any(line.startswith("apple") for line in stdout)
+
+
+def test_plugin_dispatcher_no_plugins(capfd, home, dotfiles, run_dotbot):
+    """Verify that plugins instantiating Dispatcher without plugins work."""
+
+    plugin_file = os.path.join(
+        os.path.dirname(os.path.abspath(__file__)), "dotbot_plugin_dispatcher_no_plugins.py"
+    )
+    shutil.copy(plugin_file, os.path.join(dotfiles.directory, "plugin.py"))
+    dotfiles.write_config([{"dispatch": [{"shell": [{"command": "echo apple", "stdout": True}]}]}])
+    run_dotbot("--plugin", os.path.join(dotfiles.directory, "plugin.py"))
+
+    stdout = capfd.readouterr().out.splitlines()
+    assert any(line.startswith("apple") for line in stdout)