Prevents duplicate loading of plugins

In cases of multiple load_plugins calls
Adds test for future proofing

glue/main.py

@@ -49,7 +49,7 @@ def load_plugins(splash=None, require_qt_plugins=False, plugins_to_load=None):
     config = PluginConfig.load()
 
     if plugins_to_load is None:
-        plugins_to_load = [i.value for i in list(iter_plugin_entry_points())]
+        plugins_to_load = [i.module for i in list(iter_plugin_entry_points())]
         if require_qt_plugins:
             plugins_to_require = [*REQUIRED_PLUGINS, *REQUIRED_PLUGINS_QT]
         else:
@@ -59,7 +59,8 @@ def load_plugins(splash=None, require_qt_plugins=False, plugins_to_load=None):
     n_plugins = len(plugins_to_require)
 
     for i_plugin, item in enumerate(list(iter_plugin_entry_points())):
-        if item.value.replace(':setup', '') in plugins_to_load:
+
+        if item.module in plugins_to_load:
             if item.module not in _installed_plugins:
                 _installed_plugins.add(item.name)
 

glue/tests/test_main.py

@@ -0,0 +1,20 @@
+from unittest.mock import patch
+
+from glue.main import load_plugins
+
+
+def test_no_duplicate_loading(capsys):
+    """
+    Regression test for duplicated loading of plugins
+    on subsequent calls of `load_plugins()` after initial
+    glue-qt startup.
+
+    """
+    from glue.logger import logger
+
+    with patch.object(logger, 'info') as info:
+        load_plugins()
+
+    for acall in info.call_args_list:
+        if 'Loading plugin' in acall[0][0]:
+            assert 'failed' in acall[0][0]