fix: handle duplicate adapter entries (#1012)

Signed-off-by: Andreas Bichinger <andreas.bichinger@gmail.com>

persist/adapter.go

@@ -44,8 +44,10 @@ func LoadPolicyLine(line string, m model.Model) {
 func LoadPolicyArray(rule []string, m model.Model) {
 	key := rule[0]
 	sec := key[:1]
-	m[sec][key].Policy = append(m[sec][key].Policy, rule[1:])
-	m[sec][key].PolicyMap[strings.Join(rule[1:], model.DefaultSep)] = len(m[sec][key].Policy) - 1
+	if m.HasPolicy(sec, key, rule[1:]) {
+		return
+	}
+	m.AddPolicy(sec, key, rule[1:])
 }
 
 // Adapter is the interface for Casbin adapters.

persist/persist_test.go

@@ -1,9 +1,53 @@
-package persist
+// Copyright 2017 The casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package persist_test
 
 import (
 	"testing"
+
+	"github.com/casbin/casbin/v2"
+	"github.com/casbin/casbin/v2/model"
+	"github.com/casbin/casbin/v2/persist"
 )
 
 func TestPersist(t *testing.T) {
 	//No tests yet
 }
+
+func testRuleCount(t *testing.T, model model.Model, expected int, sec string, ptype string, tag string) {
+	t.Helper()
+
+	ruleCount := len(model[sec][ptype].Policy)
+	if ruleCount != expected {
+		t.Errorf("[%s] rule count: %d, expected %d", tag, ruleCount, expected)
+	}
+}
+
+func TestDuplicateRuleInAdapter(t *testing.T) {
+	e, _ := casbin.NewEnforcer("../examples/basic_model.conf")
+
+	_, _ = e.AddPolicy("alice", "data1", "read")
+	_, _ = e.AddPolicy("alice", "data1", "read")
+
+	testRuleCount(t, e.GetModel(), 1, "p", "p", "AddPolicy")
+
+	e.ClearPolicy()
+
+	//simulate adapter.LoadPolicy with duplicate rules
+	persist.LoadPolicyArray([]string{"p", "alice", "data1", "read"}, e.GetModel())
+	persist.LoadPolicyArray([]string{"p", "alice", "data1", "read"}, e.GetModel())
+
+	testRuleCount(t, e.GetModel(), 1, "p", "p", "LoadPolicyArray")
+}