Render correct template in API (#1404)

* Explicitly render templates of correct blueprint

* Remove unused constant

connexion/apis/flask_api.py

@@ -4,6 +4,7 @@
 """
 
 import logging
+import pathlib
 import warnings
 from typing import Any
 
@@ -296,7 +297,13 @@ def console_ui_home(self):
         }
         if self.options.openapi_console_ui_config is not None:
             template_variables['configUrl'] = 'swagger-ui-config.json'
-        return flask.render_template('index.j2', **template_variables)
+
+        # Use `render_template_string` instead of `render_template` to circumvent the flask
+        # template lookup mechanism and explicitly render the template of the current blueprint.
+        # https://github.com/zalando/connexion/issues/1289#issuecomment-884105076
+        template_dir = pathlib.Path(self.options.openapi_console_ui_from_dir)
+        index_path = template_dir / 'index.j2'
+        return flask.render_template_string(index_path.read_text(), **template_variables)
 
     def console_ui_static_files(self, filename):
         """

connexion/options.py

@@ -3,7 +3,6 @@
 """
 
 import logging
-import pathlib
 from typing import Optional  # NOQA
 
 try:
@@ -13,7 +12,6 @@
 
 from connexion.decorators.uri_parsing import AbstractURIParser
 
-MODULE_PATH = pathlib.Path(__file__).absolute().parent
 NO_UI_MSG = """The swagger_ui directory could not be found.
     Please install connexion with extra install: pip install connexion[swagger-ui]
     or provide the path to your local installation by passing swagger_path=<your path>