feat: remove subtree (#17647) (#17954)

* feat: remove subtree

* test: remove_subtree

(cherry picked from commit d05ed27a01)

Co-authored-by: Raffael Meyer <14891507+barredterra@users.noreply.github.com>

frappe/tests/test_nestedset.py

@@ -12,6 +12,7 @@ from frappe.utils.nestedset import (
 	NestedSetRecursionError,
 	get_descendants_of,
 	rebuild_tree,
+	remove_subtree,
 )
 
 records = [
@@ -206,6 +207,10 @@ class TestNestedSet(FrappeTestCase):
 		with self.assertRaises(NestedSetChildExistsError):
 			frappe.delete_doc("Test Tree DocType", "Parent 1")
 
+	def test_remove_subtree(self):
+		remove_subtree("Test Tree DocType", "Parent 2")
+		self.test_basic_tree()
+
 	def test_merge_groups(self):
 		global records
 		el = {"some_fieldname": "Parent 2", "parent_test_tree_doctype": "Root Node", "is_group": 1}

frappe/utils/nestedset.py

@@ -237,6 +237,28 @@ def validate_loop(doctype, name, lft, rgt):
 		frappe.throw(_("Item cannot be added to its own descendents"), NestedSetRecursionError)
 
 
+def remove_subtree(doctype: str, name: str, throw=True):
+	"""Remove doc and all its children."""
+	frappe.has_permission(doctype, ptype="delete", throw=throw)
+
+	# Determine the `lft` and `rgt` of the subtree to be removed.
+	lft, rgt = frappe.db.get_value(doctype, name, ["lft", "rgt"])
+
+	# Delete the subtree by removing all nodes whose values for `lft` and `rgt`
+	# lie within above values or match them.
+	frappe.db.delete(doctype, {"lft": (">=", lft), "rgt": ("<=", rgt)})
+
+	# The width of the subtree is calculated as the difference between `rgt` and
+	# `lft` plus 1.
+	width = rgt - lft + 1
+
+	# All `lft` and `rgt` values, that are greater than the `rgt` of the removed
+	# subtree, must be reduced by the width of the subtree.
+	table = frappe.qb.DocType(doctype)
+	frappe.qb.update(table).set(table.lft, table.lft - width).where(table.lft > rgt).run()
+	frappe.qb.update(table).set(table.rgt, table.rgt - width).where(table.rgt > rgt).run()
+
+
 class NestedSet(Document):
 	def __setup__(self):
 		if self.meta.get("nsm_parent_field"):