Make set of plugins available in context

This is useful for plugins like dotbot-if [1] that want to instantiate
their own Dispatcher. Previously, the Dispatcher found the set of
available plugins on its own, but as of
b5499c7dc5, this was changed so that
plugins are passed in.

Given that it has been over two years since this behavior has been
broken/changed, reverting to the previous behavior of having the
Dispatcher auto-load plugins might not be ideal, which is why this patch
instead makes the set of plugins available via the Context for plugins
to use.

This was reported in the Dotbot repository [2], and earlier in dotbot-if
[3]. dotbot-if is currently using a workaround [4] that was originally
implemented in dotbot-ifplatform [5].

[1]: https://github.com/wonderbeyond/dotbot-if
[2]: https://github.com/anishathalye/dotbot/issues/339
[3]: https://github.com/wonderbeyond/dotbot-if/issues/1
[4]: https://github.com/wonderbeyond/dotbot-if/pull/2
[5]: e35b5c0d71

dotbot/context.py

@@ -8,11 +8,11 @@ class Context:
     Contextual data and information for plugins.
     """
 
-    def __init__(self, base_directory, options=Namespace()):
+    def __init__(self, base_directory, options=Namespace(), plugins=None):
         self._base_directory = base_directory
         self._defaults = {}
         self._options = options
-        pass
+        self._plugins = plugins
 
     def set_base_directory(self, base_directory):
         self._base_directory = base_directory
@@ -31,3 +31,7 @@ class Context:
 
     def options(self):
         return copy.deepcopy(self._options)
+
+    def plugins(self):
+        # shallow copy is ok here
+        return copy.copy(self._plugins)

dotbot/dispatcher.py

@@ -17,18 +17,18 @@ class Dispatcher:
         plugins=None,
     ):
         self._log = Messenger()
-        self._setup_context(base_directory, options)
+        self._setup_context(base_directory, options, plugins)
         plugins = plugins or []
         self._plugins = [plugin(self._context) for plugin in plugins]
         self._only = only
         self._skip = skip
         self._exit = exit_on_failure
 
-    def _setup_context(self, base_directory, options):
+    def _setup_context(self, base_directory, options, plugins):
         path = os.path.abspath(os.path.expanduser(base_directory))
         if not os.path.exists(path):
             raise DispatchError("Nonexistent base directory")
-        self._context = Context(path, options)
+        self._context = Context(path, options, plugins)
 
     def dispatch(self, tasks):
         success = True

tests/dotbot_plugin_context_plugin.py

@@ -0,0 +1,18 @@
+# https://github.com/anishathalye/dotbot/issues/339
+# plugins should be able to instantiate a Dispatcher with all the 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(),
+            plugins=self._context.plugins(),
+        )
+        return dispatcher.dispatch(data)

tests/test_cli.py

@@ -170,3 +170,17 @@ def test_disable_builtin_plugins(home, dotfiles, run_dotbot):
         run_dotbot("--disable-built-in-plugins")
 
     assert not os.path.exists(os.path.join(home, ".f"))
+
+
+def test_plugin_context_plugin(capfd, home, dotfiles, run_dotbot):
+    """Verify that the plugin context is available to plugins."""
+
+    plugin_file = os.path.join(
+        os.path.dirname(os.path.abspath(__file__)), "dotbot_plugin_context_plugin.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)