From 691eb31b6159fad45d7d2d6085ce84643ede8823 Mon Sep 17 00:00:00 2001
From: Sagar Vora <sagar@resilient.tech>
Date: Fri, 5 Jan 2024 10:07:14 +0530
Subject: [PATCH] fix: delete existing children first to avoid
 `UniqueValidationError`

---
 frappe/model/document.py | 45 ++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/frappe/model/document.py b/frappe/model/document.py
index 1201d3755b0..ec0799e99ff 100644
--- a/frappe/model/document.py
+++ b/frappe/model/document.py
@@ -420,36 +420,35 @@ def update_children(self):
 
 	def update_child_table(self, fieldname: str, df: Optional["DocField"] = None):
 		"""sync child table for given fieldname"""
-		rows = []
 		df: "DocField" = df or self.meta.get_field(fieldname)
+		all_rows = self.get(df.fieldname)
 
-		for d in self.get(df.fieldname):
-			d: Document
-			d.db_update()
-			rows.append(d.name)
-
-		if (
-			df.options in (self.flags.ignore_children_type or [])
+		# delete rows that do not match the ones in the document
+		# if the doctype isn't in ignore_children_type flag and isn't virtual
+		if not (
+			df.options in (self.flags.ignore_children_type or ())
 			or frappe.get_meta(df.options).is_virtual == 1
 		):
-			# do not delete rows for this because of flags
-			# hack for docperm :(
-			return
+			existing_row_names = [row.name for row in all_rows if row.name and not row.is_new()]
+
+			tbl = frappe.qb.DocType(df.options)
+			qry = (
+				frappe.qb.from_(tbl)
+				.where(tbl.parent == self.name)
+				.where(tbl.parenttype == self.doctype)
+				.where(tbl.parentfield == fieldname)
+				.delete()
+			)
 
-		# delete rows that do not match the ones in the document
-		tbl = frappe.qb.DocType(df.options)
-		qry = (
-			frappe.qb.from_(tbl)
-			.where(tbl.parent == self.name)
-			.where(tbl.parenttype == self.doctype)
-			.where(tbl.parentfield == fieldname)
-			.delete()
-		)
+			if existing_row_names:
+				qry = qry.where(tbl.name.notin(existing_row_names))
 
-		if rows:
-			qry = qry.where(tbl.name.notin(rows))
+			qry.run()
 
-		qry.run()
+		# update / insert
+		for d in all_rows:
+			d: Document
+			d.db_update()
 
 	def get_doc_before_save(self) -> "Document":
 		return getattr(self, "_doc_before_save", None)