Separate module importing from plugin identification

This change allows the test framework to reliably specify
which plugins to load and use within the same process.

Previously, plugins were loaded by importing files and then
accessing the Plugin class' list of subclasses.
Now, it's possible to run dotbot multiple times without
plugins accruing across runs with different configurations
and CLI arguments.

In addition, this fixes some circular imports that were
previously avoided because plugins were imported in a function.

dotbot/cli.py

@@ -1,4 +1,4 @@
-import os, glob
+import glob
 import sys
 
 from argparse import ArgumentParser, RawTextHelpFormatter
@@ -6,6 +6,7 @@ from .config import ConfigReader, ReadingError
 from .dispatcher import Dispatcher, DispatchError
 from .messenger import Messenger
 from .messenger import Level
+from .plugins import Clean, Create, Link, Shell
 from .util import module
 
 import dotbot
@@ -118,9 +119,10 @@ def main():
         else:
             log.use_color(sys.stdout.isatty())
 
+        plugins = []
         plugin_directories = list(options.plugin_dirs)
         if not options.disable_built_in_plugins:
-            from .plugins import Clean, Create, Link, Shell
+            plugins.extend([Clean, Create, Link, Shell])
         plugin_paths = []
         for directory in plugin_directories:
             for plugin_path in glob.glob(os.path.join(directory, "*.py")):
@@ -129,7 +131,7 @@ def main():
             plugin_paths.append(plugin_path)
         for plugin_path in plugin_paths:
             abspath = os.path.abspath(plugin_path)
-            module.load(abspath)
+            plugins.extend(module.load(abspath))
         if not options.config_file:
             log.error("No configuration file specified")
             exit(1)
@@ -151,6 +153,7 @@ def main():
             skip=options.skip,
             exit_on_failure=options.exit_on_failure,
             options=options,
+            plugins=plugins,
         )
         success = dispatcher.dispatch(tasks)
         if success:

dotbot/dispatcher.py

@@ -7,11 +7,12 @@ from .context import Context
 
 class Dispatcher(object):
     def __init__(
-        self, base_directory, only=None, skip=None, exit_on_failure=False, options=Namespace()
+        self, base_directory, only=None, skip=None, exit_on_failure=False, options=Namespace(), plugins=None,
     ):
         self._log = Messenger()
         self._setup_context(base_directory, options)
-        self._load_plugins()
+        plugins = plugins or []
+        self._plugins = [plugin(self._context) for plugin in plugins]
         self._only = only
         self._skip = skip
         self._exit = exit_on_failure
@@ -65,9 +66,6 @@ class Dispatcher(object):
                         return False
         return success
 
-    def _load_plugins(self):
-        self._plugins = [plugin(self._context) for plugin in Plugin.__subclasses__()]
-
 
 class DispatchError(Exception):
     pass

dotbot/plugins/clean.py

@@ -1,10 +1,10 @@
 import os
 import sys
 
-import dotbot
+from ..plugin import Plugin
 
 
-class Clean(dotbot.Plugin):
+class Clean(Plugin):
     """
     Cleans broken symbolic links.
     """

dotbot/plugins/create.py

@@ -1,8 +1,9 @@
 import os
-import dotbot
+
+from ..plugin import Plugin
 
 
-class Create(dotbot.Plugin):
+class Create(Plugin):
     """
     Create empty paths.
     """

dotbot/plugins/link.py

@@ -2,11 +2,12 @@ import os
 import sys
 import glob
 import shutil
-import dotbot
+
-import dotbot.util
+from ..plugin import Plugin
+from ..util import shell_command
 
 
-class Link(dotbot.Plugin):
+class Link(Plugin):
     """
     Symbolically links dotfiles.
     """
@@ -139,7 +140,7 @@ class Link(dotbot.Plugin):
         return success
 
     def _test_success(self, command):
-        ret = dotbot.util.shell_command(command, cwd=self._context.base_directory())
+        ret = shell_command(command, cwd=self._context.base_directory())
         if ret != 0:
             self._log.debug("Test '%s' returned false" % command)
         return ret == 0

dotbot/plugins/shell.py

@@ -1,10 +1,8 @@
-import os
+from ..plugin import Plugin
-import subprocess
+from ..util import shell_command
-import dotbot
-import dotbot.util
 
 
-class Shell(dotbot.Plugin):
+class Shell(Plugin):
     """
     Run arbitrary shell commands.
     """
@@ -50,7 +48,7 @@ class Shell(dotbot.Plugin):
                 self._log.lowinfo("%s [%s]" % (msg, cmd))
             stdout = options.get("stdout", stdout)
             stderr = options.get("stderr", stderr)
-            ret = dotbot.util.shell_command(
+            ret = shell_command(
                 cmd,
                 cwd=self._context.base_directory(),
                 enable_stdin=stdin,

dotbot/util/module.py

@@ -1,4 +1,7 @@
-import sys, os.path
+import os
+import sys
+
+from dotbot.plugin import Plugin
 
 # We keep references to loaded modules so they don't get garbage collected.
 loaded_modules = []
@@ -7,8 +10,17 @@ loaded_modules = []
 def load(path):
     basename = os.path.basename(path)
     module_name, extension = os.path.splitext(basename)
-    plugin = load_module(module_name, path)
+    loaded_module = load_module(module_name, path)
-    loaded_modules.append(plugin)
+    plugins = []
+    for name in dir(loaded_module):
+        possible_plugin = getattr(loaded_module, name)
+        try:
+            if issubclass(possible_plugin, Plugin) and possible_plugin is not Plugin:
+                plugins.append(possible_plugin)
+        except TypeError:
+            pass
+    loaded_modules.append(loaded_module)
+    return plugins
 
 
 if sys.version_info >= (3, 5):