Enhanced flask-babel to also allow plugins to provide translated strings

This way plugins can maintain their own translations of their UIs. Some monkey patching was necessary, not the cleanest solution but it should work.

src/octoprint/server/__init__.py

@@ -59,6 +59,7 @@ import octoprint.slicing
 
 from . import util
 util.tornado.fix_ioloop_scheduling()
+util.flask.enable_plugin_translations()
 
 
 UI_API_KEY = ''.join('%02X' % ord(z) for z in uuid.uuid4().bytes)

src/octoprint/server/util/flask.py

@@ -24,6 +24,59 @@ import octoprint.users
 from werkzeug.contrib.cache import SimpleCache
 
 
+#~~ monkey patching
+
+def enable_plugin_translations():
+	import os
+	from flask import _request_ctx_stack
+	from babel import support
+	import flask.ext.babel
+
+	import octoprint.plugin
+
+	def fixed_get_translations():
+		"""Returns the correct gettext translations that should be used for
+		this request.  This will never fail and return a dummy translation
+		object if used outside of the request or if a translation cannot be
+		found.
+		"""
+		logger = logging.getLogger(__name__)
+
+		ctx = _request_ctx_stack.top
+		if ctx is None:
+			return None
+		translations = getattr(ctx, 'babel_translations', None)
+		if translations is None:
+			locale = flask.ext.babel.get_locale()
+
+			plugins = octoprint.plugin.plugin_manager().enabled_plugins
+			for name, plugin in plugins.items():
+				dirname = os.path.join(plugin.location, 'translations')
+				if not os.path.isdir(dirname):
+					continue
+
+				try:
+					plugin_translations = support.Translations.load(dirname, [locale])
+				except:
+					logger.exception("Error while trying to load translations for plugin {name}".format(**locals()))
+				else:
+					if translations is None:
+						translations = plugin_translations
+					else:
+						translations = translations.merge(plugin_translations)
+
+			dirname = os.path.join(ctx.app.root_path, 'translations')
+			core_translations = support.Translations.load(dirname, [locale])
+			if translations is None:
+				translations = core_translations
+			else:
+				translations = translations.merge(core_translations)
+
+			ctx.babel_translations = translations
+		return translations
+
+	flask.ext.babel.get_translations = fixed_get_translations
+
 #~~ passive login helper
 
 def passive_login():