Requirements PATCH: explicit null clears parent_id (issue #30)

src/opal/api/routes/requirements.py

@@ -326,7 +326,17 @@ def update_requirement(
     old_values = get_model_dict(req)
     # Nullable fields clear on explicit null (model_fields_set distinguishes
     # absent from null — issue #30); non-nullable fields keep the None-skip.
-    clearable = {"rationale", "category", "verification_method", "tbr_owner_id", "tbr_due"}
+    # parent_id clears too: a level-0 root has no parent, so promoting a child
+    # back to a root is a legitimate edit. level is a separate field and is not
+    # adjusted here — the caller sets it in the same PATCH if it should change.
+    clearable = {
+        "rationale",
+        "category",
+        "verification_method",
+        "tbr_owner_id",
+        "tbr_due",
+        "parent_id",
+    }
     for field in (
         "title",
         "statement",

tests/unit/test_se_requirements.py

@@ -753,3 +753,24 @@ def test_api_patch_explicit_null_clears_nullable_fields(client, test_user):
     assert body["tbr_due"] is None
     assert body["category"] == "propulsion"
     assert body["title"] == req["title"]  # non-nullable untouched
+
+
+def test_api_patch_explicit_null_clears_parent(client):
+    """Issue #30 — parent_id is nullable ('level-0 roots have no parent'), so a
+    child promotes back to a root on explicit null. level is independent and is
+    only changed when the caller sends it."""
+    parent = _api_create(client, title="Vehicle", level=0)
+    child = _api_create(client, title="Engine", level=1, parent_id=parent["id"])
+    assert child["parent_id"] == parent["id"]
+
+    r = client.patch(f"/api/requirements/{child['id']}", json={"parent_id": None})
+    assert r.status_code == 200, r.text
+    body = r.json()
+    assert body["parent_id"] is None
+    assert body["level"] == 1  # untouched — clearing the parent does not relevel
+
+    # It stays cleared on reload, and omitting the field leaves it alone.
+    r = client.patch(f"/api/requirements/{child['id']}", json={"title": "Engine A"})
+    assert r.status_code == 200, r.text
+    assert r.json()["parent_id"] is None
+    assert client.get(f"/api/requirements/{child['id']}").json()["parent_id"] is None