feat: waffle flag for redirecting to courseware MFE

1. This is a partial check-in.  It causes jump_to links in the header user menu to work, but doesn’t address any other dashboard links.
2. I also need to figure out the best way to test this, having not tested a toggle like this before.

lms/djangoapps/courseware/toggles.py

@@ -0,0 +1,30 @@
+"""
+Toggles for courseware in-course experience.
+"""
+
+from openedx.core.djangoapps.site_configuration import helpers as configuration_helpers
+from openedx.core.djangoapps.waffle_utils import CourseWaffleFlag, WaffleFlagNamespace
+
+# Namespace for courseware waffle flags.
+WAFFLE_FLAG_NAMESPACE = WaffleFlagNamespace(name='courseware')
+
+# Waffle flag to redirect to another learner profile experience.
+# .. toggle_name: courseware.redirect_to_microfrontend
+# .. toggle_implementation: CourseWaffleFlag
+# .. toggle_default: False
+# .. toggle_description: Supports staged rollout of a new micro-frontend-based implementation of the courseware page.
+# .. toggle_category: micro-frontend
+# .. toggle_use_cases: incremental_release, open_edx
+# .. toggle_creation_date: 2020-01-29
+# .. toggle_expiration_date: 2020-12-31
+# .. toggle_warnings: Also set settings.LEARNING_MICROFRONTEND_URL and ENABLE_COURSEWARE_MICROFRONTEND.
+# .. toggle_tickets:
+# .. toggle_status: supported
+REDIRECT_TO_COURSEWARE_MICROFRONTEND = CourseWaffleFlag(WAFFLE_FLAG_NAMESPACE, 'redirect_to_microfrontend')
+
+
+def should_redirect_to_courseware_microfrontend(course_key):
+    return (
+        configuration_helpers.get_value('ENABLE_COURSEWARE_MICROFRONTEND') and
+        REDIRECT_TO_COURSEWARE_MICROFRONTEND.is_enabled(course_key)
+    )

lms/djangoapps/courseware/url_helpers.py

@@ -2,14 +2,14 @@
 Module to define url helpers functions
 """
 
-
 import six
+from django.conf import settings
 from django.urls import reverse
 from six.moves.urllib.parse import urlencode  # pylint: disable=import-error
 
 from xmodule.modulestore.django import modulestore
 from xmodule.modulestore.search import navigation_index, path_to_location
-
+from lms.djangoapps.courseware.toggles import should_redirect_to_courseware_microfrontend
 
 def get_redirect_url(course_key, usage_key, request=None):
     """ Returns the redirect url back to courseware
@@ -25,6 +25,10 @@ def get_redirect_url(course_key, usage_key, request=None):
         Redirect url string
     """
 
+    if should_redirect_to_courseware_microfrontend(course_key):
+      path = path_to_location(modulestore(), usage_key, request, full_path=True)
+      return get_microfrontend_redirect_url(course_key, path)
+
     (
         course_key, chapter, section, vertical_unused,
         position, final_target_id
@@ -52,3 +56,39 @@ def get_redirect_url(course_key, usage_key, request=None):
         )
     redirect_url += "?{}".format(urlencode({'activate_block_id': six.text_type(final_target_id)}))
     return redirect_url
+
+def get_microfrontend_redirect_url(course_key, path):
+  """
+    The micro-frontend determines the user's position in the vertical via
+    a separate API call, so all we need here is the course_key, section, and vertical
+    IDs to format it's URL.
+
+    It is also capable of determining our section and vertical if they're not present.  Fully specifying it all is preferable, though, as the micro-frontend can save itself some work, resulting in a better user experience.
+
+    We're building a URL like this:
+
+    http://localhost:2000/course-v1:edX+DemoX+Demo_Course/block-v1:edX+DemoX+Demo_Course+type@sequential+block@19a30717eff543078a5d94ae9d6c18a5/block-v1:edX+DemoX+Demo_Course+type@vertical+block@4a1bba2a403f40bca5ec245e945b0d76
+  """
+
+  redirect_url = '{base_url}/{prefix}/{course_key}'.format(
+   base_url=settings.LEARNING_MICROFRONTEND_URL,
+   prefix='course/',
+   course_key=course_key
+  )
+
+  # The first four elements of the path list are the ones we care about here:
+  # - course
+  # - chapter
+  # - sequence
+  # - vertical
+  # We skip course because we already have it from our argument above, and we skip chapter because the micro-frontend URL doesn't include it.
+  if len(path) > 2:
+    redirect_url += '/{sequence_key}'.format(
+      sequence_key=path[2]
+    )
+  if len(path) > 3:
+    redirect_url += '/{vertical_key}'.format(
+      vertical_key=path[3]
+    )
+
+  return redirect_url

lms/envs/devstack.py

@@ -295,4 +295,4 @@ EDXNOTES_INTERNAL_API = 'http://edx.devstack.edxnotesapi:18120/api/v1'
 EDXNOTES_CLIENT_NAME = 'edx_notes_api-backend-service'
 
 ############## Settings for Microfrontends  #########################
-LEARNING_MICROFRONTEND_URL = 'http://localhost:2000/'
+LEARNING_MICROFRONTEND_URL = 'http://localhost:2000'