Fix image cache eviction for sites with subdir in baseURL

Fixes #5006

resource/image_cache.go

@@ -33,7 +33,7 @@ type imageCache struct {
 
 func (c *imageCache) isInCache(key string) bool {
 	c.mu.RLock()
-	_, found := c.store[key]
+	_, found := c.store[c.normalizeKey(key)]
 	c.mu.RUnlock()
 	return found
 }
@@ -41,6 +41,7 @@ func (c *imageCache) isInCache(key string) bool {
 func (c *imageCache) deleteByPrefix(prefix string) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
+	prefix = c.normalizeKey(prefix)
 	for k := range c.store {
 		if strings.HasPrefix(k, prefix) {
 			delete(c.store, k)
@@ -48,6 +49,16 @@ func (c *imageCache) deleteByPrefix(prefix string) {
 	}
 }
 
+func (c *imageCache) normalizeKey(key string) string {
+	// It is a path with Unix style slashes and it always starts with a leading slash.
+	key = filepath.ToSlash(key)
+	if !strings.HasPrefix(key, "/") {
+		key = "/" + key
+	}
+
+	return key
+}
+
 func (c *imageCache) clear() {
 	c.mu.Lock()
 	defer c.mu.Unlock()