fix: activate plugins in deterministic order

errbot/plugin_manager.py

@@ -5,7 +5,8 @@
 import sys
 import traceback
 from copy import deepcopy
-from importlib import machinery
+from graphlib import CycleError
+from graphlib import TopologicalSorter as BaseTopologicalSorter
 from pathlib import Path
 from typing import Any, Callable, Dict, List, Optional, Set, Tuple, Type
 
@@ -165,6 +166,12 @@ def check_errbot_version(plugin_info: PluginInfo):
 BL_PLUGINS = "bl_plugins"
 
 
+class TopologicalSorter(BaseTopologicalSorter):
+    def find_cycle(self):
+        """Wraps private method as public one."""
+        return self._find_cycle()
+
+
 class BotPluginManager(StoreMixin):
     def __init__(
         self,
@@ -420,7 +427,8 @@ def activate_non_started_plugins(self):
         """
         log.info("Activate bot plugins...")
         errors = ""
-        for name, plugin in self.plugins.items():
+        for name in self.get_plugins_activation_order():
+            plugin = self.plugins.get(name)
             try:
                 if self.is_plugin_blacklisted(name):
                     errors += (
@@ -446,6 +454,29 @@ def activate_non_started_plugins(self):
                 errors += f"Error: flow {name} failed to start: {e}.\n"
         return errors
 
+    def get_plugins_activation_order(self) -> List[str]:
+        """
+        Calculate plugin activation order, based on their dependencies.
+
+        :return: list of plugin names, in the best order to start them.
+        """
+        plugins_graph = {
+            name: set(info.dependencies) for name, info in self.plugin_infos.items()
+        }
+        plugins_in_cycle = set()
+        while 1:
+            plugins_sorter = TopologicalSorter(plugins_graph)
+            try:
+                # Return plugins which are part of a circular dependency at the end,
+                # the rest of the code expects to have all plugins returned
+                return list(plugins_sorter.static_order()) + list(plugins_in_cycle)
+            except CycleError:
+                # Remove cycle from the graph, and
+                cycle = set(plugins_sorter.find_cycle())
+                plugins_in_cycle.update(cycle)
+                for plugin_name in cycle:
+                    plugins_graph.pop(plugin_name)
+
     def _activate_plugin(self, plugin: BotPlugin, plugin_info: PluginInfo):
         """
         Activate a specific plugin with no check.

setup.py

@@ -42,6 +42,9 @@
     "deepmerge>=0.1.0",
 ]
 
+if py_version < (3, 9):
+    deps.append("graphlib-backport")
+
 src_root = os.curdir