From 587e1a4ad89da2be46368baafb4f00b3b3d0c64a Mon Sep 17 00:00:00 2001
From: shniubobo <shniubobo@outlook.com>
Date: Sat, 31 Oct 2020 20:34:45 +0800
Subject: [PATCH] Fix plugins running twice in autoreload mode

Fixes #2817
---
 pelican/plugins/_utils.py     |  3 +++
 pelican/tests/test_plugins.py | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/pelican/plugins/_utils.py b/pelican/plugins/_utils.py
index 4e6ec3c5..ffe32799 100644
--- a/pelican/plugins/_utils.py
+++ b/pelican/plugins/_utils.py
@@ -53,6 +53,9 @@ def load_legacy_plugin(plugin, plugin_paths):
     if spec is None:
         raise ImportError('Cannot import plugin `{}`'.format(plugin))
     else:
+        # Avoid loading the same plugin twice
+        if spec.name in sys.modules:
+            return sys.modules[spec.name]
         # create module object from spec
         mod = importlib.util.module_from_spec(spec)
         # place it into sys.modules cache
diff --git a/pelican/tests/test_plugins.py b/pelican/tests/test_plugins.py
index 06940884..29729539 100644
--- a/pelican/tests/test_plugins.py
+++ b/pelican/tests/test_plugins.py
@@ -131,6 +131,17 @@ class PluginTest(unittest.TestCase):
                  'normal subpackage plugin'},
                 get_plugin_names(plugins))
 
+            # ensure normal plugins are loaded only once
+            SETTINGS = {
+                'PLUGINS': ['normal_plugin'],
+                'PLUGIN_PATHS': [self._NORMAL_PLUGIN_FOLDER],
+            }
+            plugins = load_plugins(SETTINGS)
+            for plugin in load_plugins(SETTINGS):
+                # The second load_plugins() should return the same plugin
+                # objects as the first one
+                self.assertIn(plugin, plugins)
+
             # namespace plugin short
             SETTINGS = {
                 'PLUGINS': ['ns_plugin']