Change v2 req_tree to not return root node, improve OpenAPI spec #3010

ChristopherChudzicki · 2025-10-14T13:46:06Z

What are the relevant tickets?

https://github.com/mitodl/hq/issues/8763

Description (What does it do?)

Changes the req_tree property on v2/programs response to NOT include the root node.
Fixes some openapi spec issues with req_tree.

How can this be tested?

Check the v1/programs and v2/programs responses:
- on v1, req_tree should include the root node; this was not the original intent when req_tree was added, but maintains backward compatibility
- on v2, req_tree should not include the root node.
Check that the catalog programs page loads correctly
- The program catalog page on the frontend uses v2/programs; This PR changes the req_tree property on the response. However, the req_tree property was not used anywhere on the frontend from this response. (Only from v1/programs and v1/enrollments).
Check that the individual program page loads correctly.
- Individual program pages on the frontend use the v1/programs api; this was not changed, but good to check.

If you'd like to generate the API client locally, I suggest:
- check out branch cc/local-generation from mitodl/mitxonline-api-clients#48
- run BRANCH_NAME=cc/improve-req_tree-spec ./scripts/local-generate.sh

Additional Information

New code in MIT Learn that uses req_tree currently works around the inaccuracies fixed in this PR via @ts-expect-error; Upgrading the generated client will cause typechecking errors in MIT Learn, but in all cases the errors can be fixed by removing @ts-expect-error.

ChristopherChudzicki · 2025-10-14T16:04:20Z

courses/serializers/v2/programs.py

-    course = serializers.CharField(source="course_id", allow_null=True, default=None)
-    program = serializers.CharField(source="program_id", required=False)


The API currently returns integers for this.

I believe we are only using this serializer in read-only viewsets (only v2 ProgramViewSet?), and iirc DRF does not run validation on response data, only request data, which is why it hasn't caused runtime problems.

(Switching to IntegerField fixes the openapi spec, too)

ChristopherChudzicki · 2025-10-14T16:18:05Z

courses/serializers/v2/programs.py

-            ProgramRequirementNodeType.OPERATOR,
-            ProgramRequirementNodeType.COURSE,
-        )
+        choices=[x.value for x in ProgramRequirementNodeType]


There are four node types:

class ProgramRequirementNodeType(models.TextChoices): PROGRAM_ROOT = "program_root", "Program Root" # Present since beginning OPERATOR = "operator", "Operator" # Present since beginning COURSE = "course", "Course" # Present since beginning PROGRAM = "program", "Program" # Recently Added

I think PROGRAM should have been added to the serializer in #2772.

PROGRAM_ROOT has been excluded since requirements were first added.

@rhysyngsun Do you recall why PROGRAM_ROOT is excluded? I can understand we might not want people creating / adding new PROGRAM_ROOT nodes via a (not currently exposed) creation/update API. Is that the reason?

(My goal here for the OpenAPI spec accuracy; currently spec thinks req_tree can only have course and operator nodes).

PROGRAM_ROOT would never show up, it's just an anchor node for the root of the tree in the database, it's basically a pointer to the program itself. So yeah, it shouldn't be in the API schema

It does show up in the API response, e.g., https://mitxonline.mit.edu/api/v2/programs/1/, at the root:

{ "id": 1, "title": "Data, Economics, and Design of Policy: International Development", "readable_id": "program-v1:MITx+DEDP", "req_tree": [ { "data": { "node_type": "program_root", "operator": null, "operator_value": null, "program": 1, "course": null, "required_program": null, "title": "", "elective_flag": false }, "id": 1, "children": [ { "data": { "node_type": "operator", "operator": "all_of", "operator_value": null, "program": 1, "course": null, "required_program": null, "title": "Required Courses", "elective_flag": false }, "id": 2, "children": [ { "data": { "node_type": "course", "operator": null, "operator_value": null, "program": 1, "course": 1, "required_program": null, "title": null, "elective_flag": false }, "id": 4 }, { "data": { "node_type": "course", "operator": null, "operator_value": null, "program": 1, "course": 2, "required_program": null, "title": null, "elective_flag": false }, "id": 5 }, { "data": { "node_type": "course", "operator": null, "operator_value": null, "program": 1, "course": 3, "required_program": null, "title": null, "elective_flag": false }, "id": 6 } ] }, { "data": { "node_type": "operator", "operator": "min_number_of", "operator_value": "2", "program": 1, "course": null, "required_program": null, "title": "Elective Courses", "elective_flag": true }, "id": 3, "children": [ { "data": { "node_type": "course", "operator": null, "operator_value": null, "program": 1, "course": 5, "required_program": null, "title": null, "elective_flag": false }, "id": 7 }, { "data": { "node_type": "course", "operator": null, "operator_value": null, "program": 1, "course": 6, "required_program": null, "title": null, "elective_flag": false }, "id": 8 }, { "data": { "node_type": "course", "operator": null, "operator_value": null, "program": 1, "course": 4, "required_program": null, "title": null, "elective_flag": false }, "id": 20 } ] } ] } ] // Omitting other fields for brevity }

It shouldn't be returned, it's a bit silly to have an array of a single requirements tree like that. Ideally we'd redesign that but it might be too late for that unless the integration you're doing is the first usage of it.

...but it might be too late for that unless the integration you're doing is the first usage of it.

The v1 programs and enrollments apis returns the same response (for req_tree, at least) and is used on mitxonline frontend. mitodl/mit-learn#2590 will be the first usage of req_tree from the v2 enrollments API in learn or mitxonline, as far as I can tell.

So if we want to change it in the v2 api, that would be straightforward. I agree it's a bit silly for the response to be array with 1 item. I'd prefer:

no array, req_tree = root node, or

array, req_tree = root_node.children

@rhysyngsun I've updated the v2/programs response so that req_tree is an array of nodes, program.req_tree = root_node.children.

Looking back a bit at https://github.com/mitodl/mitxonline/pull/1070/files#diff-97a17b4355029f455bcde3c73bdc32a4579fc81f007ee6fb8594d0f9656effe1R390 this seems to have been the intent, and it's what the update methods on serializers expect. I don't think the update methods are actually exposed anywhere, but now the response data matches what they would use.

ChristopherChudzicki · 2025-10-16T17:48:38Z

courses/serializers/v2/programs.py

+    required_program = serializers.IntegerField(
+        source="required_program_id", allow_null=True, default=None
+    )


required_program is not new—it was added in #2772 and can be seen in the current response at https://mitxonline.mit.edu/api/v2/programs/1

In #2772 it was added to the v1 serializer but not the v2 serializer

rhysyngsun

LGTM

ChristopherChudzicki commented Oct 14, 2025

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ChristopherChudzicki added the Needs Review label Oct 14, 2025

ChristopherChudzicki mentioned this pull request Oct 14, 2025

Program Summary mitodl/mit-learn#2590

Open

ChristopherChudzicki added 2 commits October 15, 2025 11:37

improve openapi for req_tree

a1e5af0

return root children from v2 req_tree

fc54035

ChristopherChudzicki force-pushed the cc/improve-req_tree-spec branch from d62269f to dde7c6d Compare October 15, 2025 15:37

ChristopherChudzicki changed the title ~~improve openapi for req_tree~~ Change v2 req_tree to not return root node, improve OpenAPI spec Oct 15, 2025

ChristopherChudzicki force-pushed the cc/improve-req_tree-spec branch from dde7c6d to 5604d75 Compare October 15, 2025 15:44

return root children from v2 req_tree

8b6a106

ChristopherChudzicki force-pushed the cc/improve-req_tree-spec branch from 5604d75 to 8b6a106 Compare October 15, 2025 18:43

ChristopherChudzicki requested a review from rhysyngsun October 15, 2025 19:49

ChristopherChudzicki commented Oct 16, 2025

View reviewed changes

rhysyngsun self-assigned this Oct 16, 2025

rhysyngsun approved these changes Oct 16, 2025

View reviewed changes

ChristopherChudzicki merged commit 549cab3 into main Oct 16, 2025
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odlbot mentioned this pull request Oct 16, 2025

Release 0.131.6 #3015

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		course = serializers.CharField(source="course_id", allow_null=True, default=None)
		program = serializers.CharField(source="program_id", required=False)

Change v2 req_tree to not return root node, improve OpenAPI spec #3010

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