[cache] fix typed value unmarshaling

Author: capcom6

pkg/cache/memory.go

@@ -27,7 +27,7 @@ type memoryItem struct {
 	validUntil time.Time
 }
 
-func newItem(value []byte, opts options) *memoryItem {
+func newMemoryItem(value []byte, opts options) *memoryItem {
 	item := &memoryItem{
 		value:      value,
 		validUntil: opts.validUntil,
@@ -152,7 +152,7 @@ func (m *memoryCache) newItem(value []byte, opts ...Option) *memoryItem {
 	}
 	o.apply(opts...)
 
-	return newItem(value, o)
+	return newMemoryItem(value, o)
 }
 
 func (m *memoryCache) getItem(getter func() (*memoryItem, bool)) (*memoryItem, error) {

pkg/cache/redis.go

@@ -37,7 +37,7 @@ if deleteFlag then
 end
 
 if ttlTs > 0 then
-  redis.call('HExpireAt', KEYS[1], ttlTs, field)
+  redis.call('HExpireAt', KEYS[1], ttlTs, 'FIELDS', '1', field)
 elseif ttlDelta > 0 then
   local ttl = redis.call('HTTL', KEYS[1], field)
   local newTtl = ttl + ttlDelta

pkg/cache/typed.go

@@ -3,6 +3,7 @@ package cache
 import (
 	"context"
 	"fmt"
+	"reflect"
 )
 
 type Item interface {
@@ -40,30 +41,24 @@ func (c *Typed[T]) SetOrFail(ctx context.Context, key string, value T, opts ...O
 
 func (c *Typed[T]) Get(ctx context.Context, key string, opts ...GetOption) (T, error) {
 	data, err := c.storage.Get(ctx, key, opts...)
+	var zero T
 	if err != nil {
-		return *new(T), fmt.Errorf("failed to get value from cache: %w", err)
+		return zero, fmt.Errorf("failed to get value from cache: %w", err)
 	}
 
-	var value T
+	value, err := newItem[T]()
+	if err != nil {
+		return zero, err
+	}
 	if err := value.Unmarshal(data); err != nil {
-		return *new(T), fmt.Errorf("failed to unmarshal value from cache: %w", err)
+		return zero, fmt.Errorf("failed to unmarshal value from cache: %w", err)
 	}
 
 	return value, nil
 }
 
 func (c *Typed[T]) GetAndDelete(ctx context.Context, key string) (T, error) {
-	data, err := c.storage.GetAndDelete(ctx, key)
-	if err != nil {
-		return *new(T), fmt.Errorf("failed to get value from cache: %w", err)
-	}
-
-	var value T
-	if err := value.Unmarshal(data); err != nil {
-		return *new(T), fmt.Errorf("failed to unmarshal value from cache: %w", err)
-	}
-
-	return value, nil
+	return c.Get(ctx, key, AndDelete())
 }
 
 func (c *Typed[T]) Delete(ctx context.Context, key string) error {
@@ -81,9 +76,12 @@ func (c *Typed[T]) Drain(ctx context.Context) (map[string]T, error) {
 	}
 
 	items := make(map[string]T, len(data))
-	for key, value := range data {
-		var item T
-		if err := item.Unmarshal(value); err != nil {
+	for key, raw := range data {
+		item, err := newItem[T]()
+		if err != nil {
+			return nil, err
+		}
+		if err := item.Unmarshal(raw); err != nil {
 			return nil, fmt.Errorf("failed to unmarshal value from cache: %w", err)
 		}
 
@@ -96,3 +94,20 @@ func (c *Typed[T]) Drain(ctx context.Context) (map[string]T, error) {
 func (c *Typed[T]) Close() error {
 	return c.storage.Close()
 }
+
+func newItem[T Item]() (T, error) {
+	var zero T
+
+	t := reflect.TypeOf((*T)(nil)).Elem()
+	if t.Kind() != reflect.Ptr {
+		return zero, fmt.Errorf("cache: type %s must be a pointer", t.String())
+	}
+
+	v := reflect.New(t.Elem())
+	item, ok := v.Interface().(T)
+	if !ok {
+		return zero, fmt.Errorf("cache: cannot create value of type %s", t.String())
+	}
+
+	return item, nil
+}