Prevent invalid file in Environment plugins directory from disabling Trac instance

[Ryan J Ollos]

imp.load_source can raise a SystemExit exception when there is an invalid file in the Environment's plugins directory. A common scenario seems to be that the user will select setup.py with the plugin installation file picker on the Plugins admin panel.

The patch might be as simple as (needs more testing):

trac/loader.py

@@ -87 +87 @@
                     env.log.debug('Loading file plugin %s from %s',
                                   plugin_name, plugin_file)
                     if plugin_name not in sys.modules:
-                        module = imp.load_source(plugin_name, plugin_file)
+                        try:
+                            imp.load_source(plugin_name, plugin_file)
+                        except SystemExit, e:
+                            env.log.warn("Can't load file plugin %s: %s",
+                                         plugin_file, exception_to_unicode(e))
                     if path == auto_enable:
                         _enable_plugin(env, plugin_name)
                 except Exception, e:

The issue has come up a few times recently:

• ​gmessage:trac-users:xqH_Rigciw0/MX7SEIVkWZAJ
• ​gmessage:trac-users:cXiWmefH7Tg/1tDa6uV0VXUJ
• ​gmessage:trac-dev:2FpBrUdw8ho/fNLCwDBXWegJ
• ​th:comment:2:ticket:12055
• comment:9:ticket:9390
• ​th:#12416

[Ryan J Ollos]

Here's a relevant TODO tags/trac-1.0.2/trac/admin/web_ui.py@:500#L466​. Validating the upload sounds like a good idea in addition to protecting against an invalid file in the environment plugins directory.

[Ryan J Ollos]

Another report of this issue in ​SO:27905150.