navigation: Cache and copy Menu for sorting

.Site.Menus is mutated when it is sorted for now and this causes concurrency problem (#7594)
In this patch, each related sort function copies Menu before sorting to prevent
race condition.

Pages already have such a sort and cache logic and this patch is identical to it.

Closes #7594

1 files changed, 81 insertions, 0 deletions

diff --git a/navigation/menu_cache_test.go b/navigation/menu_cache_test.go
new file mode 100644
index 000000000..4bb8921bf
--- /dev/null
+++ b/navigation/menu_cache_test.go
@@ -0,0 +1,81 @@
+// Copyright 2021 The Hugo 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 navigation
+
+import (
+	"sync"
+	"sync/atomic"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func createSortTestMenu(num int) Menu {
+	menu := make(Menu, num)
+	for i := 0; i < num; i++ {
+		m := &MenuEntry{}
+		menu[i] = m
+	}
+	return menu
+}
+
+func TestMenuCache(t *testing.T) {
+	t.Parallel()
+	c := qt.New(t)
+	c1 := newMenuCache()
+
+	changeFirst := func(m Menu) {
+		m[0].title = "changed"
+	}
+
+	var o1 uint64
+	var o2 uint64
+
+	var wg sync.WaitGroup
+
+	var l1 sync.Mutex
+	var l2 sync.Mutex
+
+	var testMenuSets []Menu
+
+	for i := 0; i < 50; i++ {
+		testMenuSets = append(testMenuSets, createSortTestMenu(i+1))
+	}
+
+	for j := 0; j < 100; j++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for k, menu := range testMenuSets {
+				l1.Lock()
+				m, ca := c1.get("k1", nil, menu)
+				c.Assert(ca, qt.Equals, !atomic.CompareAndSwapUint64(&o1, uint64(k), uint64(k+1)))
+				l1.Unlock()
+				m2, c2 := c1.get("k1", nil, m)
+				c.Assert(c2, qt.Equals, true)
+				c.Assert(menuEqual(m, m2), qt.Equals, true)
+				c.Assert(menuEqual(m, menu), qt.Equals, true)
+				c.Assert(m, qt.Not(qt.IsNil))
+
+				l2.Lock()
+				m3, c3 := c1.get("k2", changeFirst, menu)
+				c.Assert(c3, qt.Equals, !atomic.CompareAndSwapUint64(&o2, uint64(k), uint64(k+1)))
+				l2.Unlock()
+				c.Assert(m3, qt.Not(qt.IsNil))
+				c.Assert("changed", qt.Equals, m3[0].title)
+			}
+		}()
+	}
+	wg.Wait()
+}