fix: Validation added to restrict multiple course page with same course

[marslanabdulrauf]

What are the relevant tickets?

https://github.com/mitodl/hq/issues/6749

Description (What does it do?)

This PR adds Validation to restrict creating multiple course pages with same course object

Screenshots (if appropriate):

How can this be tested?

Scenario 1:

1. Create a CoursePage in CMS
2. Try to create ExternalCoursePage with same course -- You should get error

Scenario 2:

1. Create an ExternalCoursePage in CMS
2. Try to create CoursePage with the same course -- You should get error

[Anas12091101]

Thanks @marslanabdulrauf for creating this PR. I have some questions:

In addition to applying validations, can we filter courses using the is_external field when creating CoursePage and ExternalCoursePage?

This would ensure that only internal courses appear in the course list for CoursePage, while external courses appear in the list for ExternalCoursePage.

[Anas12091101]

Suggested change

	def test_external_course_page_with_same_course_run_in_internal_course_page():
	"""
	Tests that a CoursePage with the same course run as another CoursePage.
	"""
	course_page = CoursePageFactory.create()
	with pytest.raises(ValidationError) as context:
	ExternalCoursePageFactory.create(course=course_page.course)
	assert (
	str(context.value)
	== "{'__all__': ['There is already an internal course page associated with this course.']}"
	)
	def test_internal_course_page_with_same_course_run_in_external_course_page():
	"""
	Tests that an ExternalCoursePage with the same course run as another ExternalCoursePage.
	"""
	external_course_page = ExternalCoursePageFactory.create()
	with pytest.raises(ValidationError) as context:
	CoursePageFactory.create(course=external_course_page.course)
	assert (
	str(context.value)
	== "{'__all__': ['There is already an external course page associated with this course.']}"
	)
	@pytest.mark.parametrize(
	"existing_factory, new_factory, expected_error",
	[
	(CoursePageFactory, ExternalCoursePageFactory,
	"{'__all__': ['There is already an internal course page associated with this course.']}"),
	(ExternalCoursePageFactory, CoursePageFactory,
	"{'__all__': ['There is already an external course page associated with this course.']}"),
	]
	)
	def test_prevent_duplicate_course_pages(existing_factory, new_factory, expected_error):
	"""
	Tests that creating a course page with the same course run as another course page raises a ValidationError.
	"""
	existing_page = existing_factory.create()
	with pytest.raises(ValidationError) as context:
	new_factory.create(course=existing_page.course)
	assert str(context.value) == expected_error

We can parameterize the test here to avoid code duplication.

[Anas12091101]

Please add a doc string

[Anas12091101]

How do we plan to handle the existing incorrect data? Should the wrong page be deleted or unpublished? In a similar case, Bon previously unpublished the course page: https://github.com/mitodl/hq/issues/6107#issuecomment-2632165868.

@cachob, I'd love to hear your thoughts on this.

If we decide to go with unpublishing, we may need to update the logic accordingly.

[cachob]

Let's delete the pages - one of our objectives to make the CMS tidy.

[marslanabdulrauf]

As per our discussion (@arslanashraf7, @Anas12091101), filtering courses based on the course page could lead to unexpected scenarios. For now, we will stick with raising a validation error.

[marslanabdulrauf]

Hi @cachob,

I queried the RC instance and did not find any duplicates.

Since I don't have Production access, could you please run the following query on Production to identify any duplicate CoursePage or ExternalCoursePage instances? If duplicates exist, we can then determine which pages need to be deleted.

from cms.models import CoursePage, ExternalCoursePage

# Find courses that have both an internal and external course page
duplicate_courses = CoursePage.objects.filter(
    course__in=ExternalCoursePage.objects.values_list("course", flat=True)
).values_list("course__id", flat=True)

# Fetch the duplicate CoursePage and ExternalCoursePage instances
duplicate_internal_pages = CoursePage.objects.filter(course_id__in=duplicate_courses)
duplicate_external_pages = ExternalCoursePage.objects.filter(course_id__in=duplicate_courses)

Let me know if you find any duplicates or if further help is needed. Thanks!