From fcdef2d96cdb51ac59cbca0b33f898916c04aed6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maxime=20=E2=80=9Cpep=E2=80=9D=20Buquet?= <pep@bouah.net>
Date: Sat, 11 Apr 2020 18:11:24 +0200
Subject: [PATCH] plugins: Add dependencies support
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Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>
---
 poezio/core/core.py      |  4 ++--
 poezio/plugin.py         |  6 ++++++
 poezio/plugin_manager.py | 45 +++++++++++++++++++++++++++++++++++++++-
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/poezio/core/core.py b/poezio/core/core.py
index 525d02a6..14852ac2 100644
--- a/poezio/core/core.py
+++ b/poezio/core/core.py
@@ -518,10 +518,10 @@ class Core:
         plugins = config.get('plugins_autoload')
         if ':' in plugins:
             for plugin in plugins.split(':'):
-                self.plugin_manager.load(plugin)
+                self.plugin_manager.load(plugin, unload_first=False)
         else:
             for plugin in plugins.split():
-                self.plugin_manager.load(plugin)
+                self.plugin_manager.load(plugin, unload_first=False)
         self.plugins_autoloaded = True
 
     def start(self):
diff --git a/poezio/plugin.py b/poezio/plugin.py
index 61e0ea87..81c849b4 100644
--- a/poezio/plugin.py
+++ b/poezio/plugin.py
@@ -3,6 +3,8 @@ Define the PluginConfig and Plugin classes, plus the SafetyMetaclass.
 These are used in the plugin system added in poezio 0.7.5
 (see plugin_manager.py)
 """
+
+from typing import Set
 from asyncio import iscoroutinefunction
 from functools import partial
 from configparser import RawConfigParser
@@ -399,7 +401,11 @@ class BasePlugin(object, metaclass=SafetyMetaclass):
     Class that all plugins derive from.
     """
 
+    # Internal use only
+    _unloading = False
+
     default_config = None
+    dependencies: Set[str] = set()
 
     def __init__(self, name, plugin_api, core, plugins_conf_dir):
         self.__name = name
diff --git a/poezio/plugin_manager.py b/poezio/plugin_manager.py
index 75a6b4a3..c44a8ecc 100644
--- a/poezio/plugin_manager.py
+++ b/poezio/plugin_manager.py
@@ -7,6 +7,7 @@ plugin env.
 
 import logging
 import os
+from typing import Dict, Set
 from importlib import import_module, machinery
 from pathlib import Path
 from os import path
@@ -27,6 +28,8 @@ class PluginManager:
     And keeps track of everything the plugin has done through the API.
     """
 
+    rdeps: Dict[str, Set[str]] = {}
+
     def __init__(self, core):
         self.core = core
         # module name -> module object
@@ -58,10 +61,25 @@ class PluginManager:
         for plugin in set(self.plugins.keys()):
             self.unload(plugin, notify=False)
 
-    def load(self, name: str, notify=True):
+    def set_rdeps(self, name):
+        """
+        Runs through plugin dependencies to build the reverse dependencies table.
+        """
+
+        if name not in self.rdeps:
+            self.rdeps[name] = set()
+        for dep in self.plugins[name].dependencies:
+            if dep not in self.rdeps:
+                self.rdeps[dep] = {name}
+            else:
+                self.rdeps[dep].add(name)
+
+    def load(self, name: str, notify=True, unload_first=True):
         """
         Load a plugin.
         """
+        if not unload_first and name in self.plugins:
+            return None
         if name in self.plugins:
             self.unload(name)
 
@@ -109,8 +127,20 @@ class PluginManager:
         self.event_handlers[name] = []
         try:
             self.plugins[name] = None
+
+            for dep in module.Plugin.dependencies:
+                self.load(dep, unload_first=False)
+                if dep not in self.plugins:
+                    log.debug(
+                        'Plugin %s couldn\'t load because of dependency %s',
+                        name, dep
+                    )
+                    return None
+
             self.plugins[name] = module.Plugin(name, self.plugin_api, self.core,
                                                self.plugins_conf_dir)
+            self.set_rdeps(name)
+
         except Exception as e:
             log.error('Error while loading the plugin %s', name, exc_info=True)
             if notify:
@@ -122,8 +152,20 @@ class PluginManager:
                 self.core.information('Plugin %s loaded' % name, 'Info')
 
     def unload(self, name: str, notify=True):
+        """
+        Unloads plugin as well as plugins depending on it.
+        """
+
         if name in self.plugins:
             try:
+                self.plugins[name]._unloading = True  # Prevents loops
+                for rdep in self.rdeps[name].copy():
+                    if rdep in self.plugins and not self.plugins[rdep]._unloading:
+                        self.unload(rdep)
+                        if rdep in self.plugins:
+                            log.debug('Failed to unload reverse dependency %s first.', rdep)
+                            return None
+
                 for command in self.commands[name].keys():
                     del self.core.commands[command]
                 for key in self.keys[name].keys():
@@ -143,6 +185,7 @@ class PluginManager:
                 if self.plugins[name] is not None:
                     self.plugins[name].unload()
                 del self.plugins[name]
+                del self.rdeps[name]
                 del self.commands[name]
                 del self.keys[name]
                 del self.tab_commands[name]