Merge pull request #7556 from vmg/vmg/cache-init

cache: handle all possible initialization cases

go/cache/cache.go

@@ -47,15 +47,21 @@ type cachedObject interface {
 // implementation.
 func NewDefaultCacheImpl(cfg *Config) Cache {
 	switch {
-	case cfg == nil || (cfg.MaxEntries == 0 && cfg.MaxMemoryUsage == 0):
+	case cfg == nil:
 		return &nullCache{}
 
 	case cfg.LFU:
+		if cfg.MaxEntries == 0 || cfg.MaxMemoryUsage == 0 {
+			return &nullCache{}
+		}
 		return NewRistrettoCache(cfg.MaxEntries, cfg.MaxMemoryUsage, func(val interface{}) int64 {
 			return val.(cachedObject).CachedSize(true)
 		})
 
 	default:
+		if cfg.MaxEntries == 0 {
+			return &nullCache{}
+		}
 		return NewLRUCache(cfg.MaxEntries, func(_ interface{}) int64 {
 			return 1
 		})

go/cache/cache_test.go

@@ -0,0 +1,47 @@
+package cache
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"vitess.io/vitess/go/cache/ristretto"
+)
+
+func TestNewDefaultCacheImpl(t *testing.T) {
+	assertNullCache := func(t *testing.T, cache Cache) {
+		_, ok := cache.(*nullCache)
+		require.True(t, ok)
+	}
+
+	assertLFUCache := func(t *testing.T, cache Cache) {
+		_, ok := cache.(*ristretto.Cache)
+		require.True(t, ok)
+	}
+
+	assertLRUCache := func(t *testing.T, cache Cache) {
+		_, ok := cache.(*LRUCache)
+		require.True(t, ok)
+	}
+
+	tests := []struct {
+		cfg    *Config
+		verify func(t *testing.T, cache Cache)
+	}{
+		{&Config{MaxEntries: 0, MaxMemoryUsage: 0, LFU: false}, assertNullCache},
+		{&Config{MaxEntries: 0, MaxMemoryUsage: 0, LFU: true}, assertNullCache},
+		{&Config{MaxEntries: 100, MaxMemoryUsage: 0, LFU: false}, assertLRUCache},
+		{&Config{MaxEntries: 0, MaxMemoryUsage: 1000, LFU: false}, assertNullCache},
+		{&Config{MaxEntries: 100, MaxMemoryUsage: 1000, LFU: false}, assertLRUCache},
+		{&Config{MaxEntries: 100, MaxMemoryUsage: 0, LFU: true}, assertNullCache},
+		{&Config{MaxEntries: 100, MaxMemoryUsage: 1000, LFU: true}, assertLFUCache},
+		{&Config{MaxEntries: 0, MaxMemoryUsage: 1000, LFU: true}, assertNullCache},
+	}
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("%d.%d.%v", tt.cfg.MaxEntries, tt.cfg.MaxMemoryUsage, tt.cfg.LFU), func(t *testing.T) {
+			cache := NewDefaultCacheImpl(tt.cfg)
+			tt.verify(t, cache)
+		})
+	}
+}