fix(journal entry): validate opening entry against pcv on save

(cherry picked from commit f8aa4c730c)

# Conflicts:
#	erpnext/accounts/doctype/journal_entry/journal_entry.py
#	erpnext/accounts/general_ledger.py

erpnext/accounts/doctype/journal_entry/journal_entry.py

@@ -21,6 +21,7 @@ from erpnext.accounts.doctype.repost_accounting_ledger.repost_accounting_ledger
 from erpnext.accounts.doctype.tax_withholding_category.tax_withholding_category import (
 	get_party_tax_withholding_details,
 )
+from erpnext.accounts.general_ledger import validate_opening_entry_against_pcv
 from erpnext.accounts.party import get_party_account
 from erpnext.accounts.utils import (
 	cancel_exchange_gain_loss_journal,
@@ -123,6 +124,9 @@ class JournalEntry(AccountsController):
 		if not self.is_opening:
 			self.is_opening = "No"
 
+		if self.is_opening == "Yes":
+			validate_opening_entry_against_pcv(self.company)
+
 		self.clearance_date = None
 
 		self.validate_party()

erpnext/accounts/general_ledger.py

@@ -802,13 +802,24 @@ def check_freezing_date(posting_date, adv_adj=False):
 				)
 
 
-def validate_against_pcv(is_opening, posting_date, company):
+def validate_opening_entry_against_pcv(company):
-	if is_opening and frappe.db.exists("Period Closing Voucher", {"docstatus": 1, "company": company}):
+	if frappe.db.exists("Period Closing Voucher", {"docstatus": 1, "company": company}):
 		frappe.throw(
-			_("Opening Entry can not be created after Period Closing Voucher is created."),
+			_(
+				"A Period Closing Voucher is already submitted and an Opening Entry can no longer be created. {0} to learn more."
+			).format(
+				'<a href="https://docs.frappe.io/erpnext/period-closing-voucher#14-pcv-and-opening-entries" target="_blank" rel="noopener">'
+				+ _("Read the docs")
+				+ "</a>"
+			),
 			title=_("Invalid Opening Entry"),
 		)
 
+
+def validate_against_pcv(is_opening, posting_date, company):
+	if is_opening:
+		validate_opening_entry_against_pcv(company)
+
 	# Local import so you don't have to touch file-level imports
 	from frappe.query_builder.functions import Max