refactor: Move get_course_by_id helper from LMS to core

This helper is used by the LMS, CMS, _and_ `openedx.core`,
so let's move it to `openedx.core` to reduce import complexity.

The following files no longer import from LMS:
- cms/djangoapps/contentstore/management/commands/edit_course_tabs.py
- lms/djangoapps/ccx/migrations/0006_set_display_name_as_override.py
- openedx/core/djangoapps/ccxcon/api.py
- openedx/core/djangoapps/verified_track_content/models.py
- openedx/features/course_experience/plugins.py

Note: The LTI XBlock has a dependency on this import path (!?);
a fix can be found here [1].

- [1] https://github.com/edx/xblock-lti-consumer/pull/154

openedx/core/djangoapps/ccxcon/api.py

@@ -13,8 +13,8 @@ from oauthlib.oauth2 import BackendApplicationClient
 from requests_oauthlib import OAuth2Session
 from rest_framework.status import HTTP_200_OK, HTTP_201_CREATED
 
-from lms.djangoapps.courseware.courses import get_course_by_id
 from openedx.core.djangoapps.models.course_details import CourseDetails
+from openedx.core.lib.courses import get_course_by_id
 from common.djangoapps.student.models import anonymous_id_for_user
 from common.djangoapps.student.roles import CourseInstructorRole
 

openedx/core/djangoapps/course_groups/cohorts.py

@@ -20,6 +20,7 @@ from eventtracking import tracker
 
 from lms.djangoapps.courseware import courses
 from openedx.core.lib.cache_utils import request_cached
+from openedx.core.lib.courses import get_course_by_id
 from common.djangoapps.student.models import get_user_by_username_or_email
 
 from .models import (
@@ -387,7 +388,7 @@ def add_cohort(course_key, name, assignment_type):
         raise ValueError(_("You cannot create two cohorts with the same name"))
 
     try:
-        course = courses.get_course_by_id(course_key)
+        course = get_course_by_id(course_key)
     except Http404:
         raise ValueError("Invalid course_key")  # lint-amnesty, pylint: disable=raise-missing-from
 
@@ -593,7 +594,7 @@ def _get_course_cohort_settings(course_key):
     try:
         course_cohort_settings = CourseCohortsSettings.objects.get(course_id=course_key)
     except CourseCohortsSettings.DoesNotExist:
-        course = courses.get_course_by_id(course_key)
+        course = get_course_by_id(course_key)
         course_cohort_settings = migrate_cohort_settings(course)
     return course_cohort_settings
 
@@ -608,7 +609,7 @@ def get_legacy_discussion_settings(course_key):  # lint-amnesty, pylint: disable
             'always_cohort_inline_discussions': course_cohort_settings.always_cohort_inline_discussions
         }
     except CourseCohortsSettings.DoesNotExist:
-        course = courses.get_course_by_id(course_key)
+        course = get_course_by_id(course_key)
         return _get_cohort_settings_from_modulestore(course)
 
 

openedx/core/djangoapps/courseware_api/views.py

@@ -29,7 +29,7 @@ from lms.djangoapps.courseware.access_response import (
     CoursewareMicrofrontendDisabledAccessError,
 )
 from lms.djangoapps.courseware.context_processor import user_timezone_locale_prefs
-from lms.djangoapps.courseware.courses import check_course_access, get_course_by_id
+from lms.djangoapps.courseware.courses import check_course_access
 from lms.djangoapps.courseware.masquerade import setup_masquerade
 from lms.djangoapps.courseware.module_render import get_module_by_usage_id
 from lms.djangoapps.courseware.tabs import get_course_tab_list
@@ -39,6 +39,7 @@ from lms.djangoapps.grades.api import CourseGradeFactory
 from lms.djangoapps.verify_student.services import IDVerificationService
 from openedx.core.lib.api.authentication import BearerAuthenticationAllowInactiveUser
 from openedx.core.lib.api.view_utils import DeveloperErrorViewMixin
+from openedx.core.lib.courses import get_course_by_id
 from openedx.core.djangoapps.programs.utils import ProgramProgressMeter
 from openedx.features.course_experience import DISPLAY_COURSE_SOCK_FLAG
 from openedx.features.content_type_gating.models import ContentTypeGatingConfig

openedx/core/djangoapps/verified_track_content/models.py

@@ -14,7 +14,6 @@ from django.utils.translation import ugettext_lazy
 from edx_django_utils.cache import RequestCache
 from opaque_keys.edx.django.models import CourseKeyField
 
-from lms.djangoapps.courseware.courses import get_course_by_id
 from openedx.core.djangoapps.course_groups.cohorts import (
     CourseCohort,
     get_course_cohorts,
@@ -23,6 +22,7 @@ from openedx.core.djangoapps.course_groups.cohorts import (
 )
 from openedx.core.djangoapps.verified_track_content.tasks import sync_cohort_with_mode
 from openedx.core.lib.cache_utils import request_cached
+from openedx.core.lib.courses import get_course_by_id
 from common.djangoapps.student.models import CourseEnrollment
 
 log = logging.getLogger(__name__)

openedx/core/lib/courses.py

@@ -4,6 +4,7 @@ Common utility functions related to courses.
 
 from django import forms
 from django.conf import settings
+from django.http import Http404
 
 from opaque_keys import InvalidKeyError
 from opaque_keys.edx.locator import CourseKey
@@ -82,3 +83,19 @@ def clean_course_id(model_form, is_required=True):
         raise forms.ValidationError(msg)
 
     return course_key
+
+
+def get_course_by_id(course_key, depth=0):
+    """
+    Given a course id, return the corresponding course descriptor.
+
+    If such a course does not exist, raises a 404.
+
+    depth: The number of levels of children for the modulestore to cache. None means infinite depth
+    """
+    with modulestore().bulk_operations(course_key):
+        course = modulestore().get_course(course_key, depth=depth)
+    if course:
+        return course
+    else:
+        raise Http404("Course not found: {}.".format(str(course_key)))

openedx/features/course_experience/plugins.py

@@ -8,8 +8,8 @@ This includes any locally defined CourseTools.
 from django.urls import reverse
 from django.utils.translation import ugettext as _
 
-from lms.djangoapps.courseware.courses import get_course_by_id
 from common.djangoapps.student.models import CourseEnrollment
+from openedx.core.lib.courses import get_course_by_id
 
 from . import DISABLE_UNIFIED_COURSE_TAB_FLAG
 from .course_tools import CourseTool